# Space Radar Journal: full text > Field notes from Space Radar, the free, open-source 3D map of everything in orbit: satellites, stations, planets and stars. Every story ends on the map, so you can go and look. # Stars with no distance, 4 383 pulsars and the farthest galaxy > Release 1.5.0 fills the sky with what the catalogues know, and says on every card how a distance was found, or that it never was. By Space Radar. Published 2026-10-31. Category: Stars & Galaxies. Tags: pulsars, stars, MoM-z14, distance, release 1.5. 4 min read. Canonical: https://blog.spaceradar.ai/stars-without-a-distance-and-the-farthest-light/ ![The Milky Way's stage with the pulsar PSR J0437-4715 selected: its card says 509 light-years and 5.76 milliseconds a turn.](/media/stars-without-a-distance-and-the-farthest-light/psr-j0437.jpg) *PSR J0437-4715, the nearest millisecond pulsar, 509 light-years away by parallax.* Release 1.5.0 fills Space Radar's sky with what the catalogues know and the map had left out: the IAU's approved star names, more than ten thousand stars whose distance has never been measured, 4 383 pulsars, magnetars, dead stars and quiet black holes, the dwarf galaxies of the Local Group, named clusters of galaxies, the farthest galaxies yet found and a thousand quasars. Every one of them is something you can search for, select and read about, and every card says how its distance was found, or that it was not. ## A star with no distance The map's 109 389 stars are each placed in 3D at the distance their parallax gives. The catalogue they come from, HYG, also lists 10 224 stars that have no parallax at all. Before this release they were simply missing. Now they are drawn as directions: points on the sky you see from a world's own stage, where you would look up and find them, but nowhere in the 3D space between the stars, because nobody knows where along that line they are. Tap one and its card opens with its brightness and its class, and no distance. The row says "Not measured", and the camera stays where it is, because there is no place to fly to. The Garnet Star in Cepheus, one of the reddest stars the eye can see, is one of them. At the Camera setting about 850 of these stars are bright enough to be drawn; the rest are fainter, and the 63 that have names can be found by search. ![The card of the Garnet Star, a red supergiant: its magnitude 4.23 and class M2Ia, and no distance.](/media/stars-without-a-distance-and-the-farthest-light/garnet-star.jpg) *The Garnet Star's card: a magnitude and a class, and no distance, because none has been measured.* The same release joins the stars to the IAU's list of approved names, so a star's card can show the name the International Astronomical Union has given it, and a search for one of the names it gave to planets finds the planet. ## Dead stars, pulsars and black holes The pulsars come from the ATNF catalogue, version 2.9.0, which lists 4 503. The map places 4 383 of them: by parallax where its error is under 20 %, by the cluster or remnant a pulsar belongs to where that is known, and otherwise by the dispersion of its radio pulses, which the card calls a model's estimate. They are small marks on a layer that is off until you turn it on. The magnetars of the McGill catalogue, the black holes of the BlackCAT tables, Gaia BH2, four record-holding white dwarfs and the 24 brown dwarfs within 20 light-years join them. Luhman 16 A, the nearest brown dwarf, is 6.5 light-years from the Sun. ![Luhman 16 A selected among the nearby stars: a brown dwarf 6.51 light-years from the Sun.](/media/stars-without-a-distance-and-the-farthest-light/luhman-16.jpg) *Luhman 16 A, a brown dwarf 6.51 light-years away: a card and a mark, with no photograph.* ## Beyond the Milky Way The Local Volume Database adds 85 confirmed dwarf galaxies of the Local Group the map did not have, which with the Milky Way, Andromeda and Triangulum makes 124 members. Thirty-five clusters of galaxies have their own records, among them the Bullet Cluster and El Gordo. A thousand of the brightest quasars of the Milliquas catalogue are on a layer of their own, with all nine known beyond a redshift of 7. At the far end are the record holders. MoM-z14, at a redshift of 14.44, is drawn where it is now, 33.9 billion light-years away. That number is a comoving distance worked out from the redshift with the Planck 2018 cosmology, and the card gives the time its light has travelled from the same redshift beside it, so the two are not confused. ![MoM-z14 selected against the oldest light, the cosmic microwave background, with its card open.](/media/stars-without-a-distance-and-the-farthest-light/mom-z14.jpg) *MoM-z14, at redshift 14.44, against the map's picture of the oldest light.* ## Why it was hard None of this may slow down the first screen. The new catalogues together weigh 247 kB compressed, and none of it is fetched when the page opens: it arrives the first time a visitor searches, opens one of these layers, follows a link to one of these objects or climbs the ladder to where they are. ## Measured, modelled, illustrative - **Measured:** positions, pulsar periods, parallax distances and redshifts, each from the catalogue or paper the card names. - **Modelled:** a pulsar's distance from its dispersion, and a galaxy's present distance from its redshift. Both cards say so. - **Illustrative:** the marks themselves. Nothing here is a 3D model except the black holes' existing portraits. ## How to try it - [PSR J0437-4715, the nearest millisecond pulsar](https://www.spaceradar.ai/#go=exotic-psr-j0437-4715) - [Luhman 16 A, the nearest brown dwarf](https://www.spaceradar.ai/#go=exotic-bd-luhman-16-a) - [MoM-z14, the farthest galaxy on the map](https://www.spaceradar.ai/#go=exotic-mom-z14) Or search for "Garnet Star", then look at its card. ## Pictures and sources Screenshots of Space Radar 1.5.1 (MIT licence) from the project's `look` workflow, probe `r15-a45`. The data: IAU WGSN star names (CC BY); HYG v4.4 (CC BY-SA 4.0); the ATNF pulsar catalogue (Manchester and others, 2005); the McGill Online Magnetar Catalog (Olausen and Kaspi, 2014); BlackCAT (Corral-Santana and others, 2016); the Local Volume Database (CC0); MCXC and Milliquas v8 through HEASARC. The work is Sara-Agent's, the project's agent, in [pull request 1312](https://github.com/Sara-Managed-Projects/space-radar/pull/1312); the quoted terms are in section 3n of [CREDITS.md](https://github.com/Sara-Managed-Projects/space-radar/blob/main/CREDITS.md). **Fly there in the 3D map:** [Fly to the nearest millisecond pulsar](https://www.spaceradar.ai/#go=exotic-psr-j0437-4715). Free, in your browser, no account. ## Sources 1. [Space Radar changelog: release 1.5.0](https://github.com/Sara-Managed-Projects/space-radar/blob/main/CHANGELOG.md) --- # Arrokoth, Kleopatra and nine more small worlds in their own shapes > Release 1.5.0 replaces the generic rock with the shapes spacecraft and radar measured for eleven small bodies, and says on every card what was seen. By Space Radar. Published 2026-10-30. Category: Solar System. Tags: asteroids, Arrokoth, Kleopatra, comets, shape models, release 1.5. 4 min read. Canonical: https://blog.spaceradar.ai/eleven-small-worlds-in-their-own-shapes/ ![Arrokoth, two reddish lobes of different sizes joined at a neck, against the Milky Way, with its card open beside it.](/media/eleven-small-worlds-in-their-own-shapes/arrokoth.jpg) *Arrokoth in release 1.5.0: New Horizons' shape model with its own brightness map, 43 au from the Sun.* Release 1.5.0 gives eleven small bodies of the Solar System the shapes that spacecraft and radar actually measured. Select one of them on the map and fly close, and the generic grey rock is replaced by a published shape model: Arrokoth's two lobes, Kleopatra's dog bone, the contact binary 1996 HW1. Each sits on its own orbit from JPL, and each card says what was seen and what was filled in. ## The eleven Five come from the missions that flew past them. Arrokoth is New Horizons' target beyond Neptune, the most distant object a spacecraft has visited, two lumps of ice and rock joined at a neck about 35 kilometres from end to end. Donaldjohanson is the main-belt asteroid NASA's Lucy flew past in April 2025, named for the discoverer of the Lucy fossil that the mission is named after; its shape is DLR's, from Lucy's pictures. The comet 67P/Churyumov-Gerasimenko and the asteroids Lutetia and Steins come from Rosetta. Six come from radar. Toutatis, Geographos, Kleopatra, Mithra, Golevka and 1996 HW1 were never visited; their outlines were worked out from the echoes of radio pulses sent from Earth by planetary radar teams; Toutatis's model, for one, is Hudson and Ostro's from Goldstone. The models are the ones NASA publishes for 3D printing. ![Donaldjohanson, a pale elongated rock with a narrow waist, seen as the map frames it.](/media/eleven-small-worlds-in-their-own-shapes/donaldjohanson.jpg) *52246 Donaldjohanson as the map frames it on arrival: DLR's shape from Lucy's flyby.* None of these ten asteroids was a place on the map before this release. The map drew a generic rock only for what JPL's close-approach table held that week, and 67P was one dot among the comets. ## Grey from albedo, relief from the source The colour of each body is not chosen by eye. Its grey follows its measured albedo, the fraction of light it reflects, through one rule for all eleven, with a tint of the same lightness for its spectral type. The albedo and its reference are written in each body's row of the registry. Arrokoth's is the published 0.21 and 67P's the published 0.065, which is why the comet looks so much darker than the asteroids beside it. Where a model had to be simplified to load quickly in a browser, the full-resolution model's surface detail was baked into a normal map inside the file, so the craters and ridges you see are the source's own and nothing is invented. Arrokoth keeps its published brightness map, softened, and its red is a modelled approximation of New Horizons' colour. ![Kleopatra, a long metal-rich asteroid shaped like a dog bone, with its card open.](/media/eleven-small-worlds-in-their-own-shapes/kleopatra.jpg) *216 Kleopatra, 276 km from end to end, from the radar shape model (Ostro and others, 2000).* ## Why it was hard Shape models come in many formats and sizes. Rosetta's full 67P model has 788 000 plates; the browser gets 40 000 with the rest of the detail carried in the normal map, and the file arrives only when you select the comet and come close. The turning was the other problem. The mission bodies turn at the pole and rate their datasets give. The radar bodies do not turn at all, because their files state no axes, and their cards say so rather than inventing a spin. ## How to try it Search the map for a name, or open one directly: - [Arrokoth, beyond Neptune](https://www.spaceradar.ai/#go=asteroid-486958) - [Kleopatra, in the main belt](https://www.spaceradar.ai/#go=asteroid-216) - [Donaldjohanson, visited by Lucy](https://www.spaceradar.ai/#go=asteroid-52246) - [1996 HW1, a near-Earth contact binary](https://www.spaceradar.ai/#go=asteroid-8567) Press "Fly to it", then drag to turn round the body. "About it" on the card says how its shape was made. ![1996 HW1, two lobes touching, a smooth radar shape seen against dark space.](/media/eleven-small-worlds-in-their-own-shapes/1996-hw1.jpg) *8567 (1996 HW1), found by radar to be a contact binary: two lobes touching.* ## Measured, modelled, reconstructed - **Measured:** the outlines, the poles and rotation rates of the mission bodies, and the orbits, which are held to JPL Horizons within 0.0002 au by the project's tests. - **Modelled:** the grey, from one rule on the albedo; the tint, from the spectral type; and the phase of every turn, which no source gives for a chosen day. - **Reconstructed:** the sides that no camera saw. Lutetia, Steins, Donaldjohanson and Arrokoth were each imaged from one side as the spacecraft went by, and their cards say which part is inferred. The radar shapes are smooth at this size, from 3 000 to 13 000 plates each: recognisable, but plain. About 54 more radar shapes, and Halley, Gaspra, Ida and Mathilde, wait on a server that refused the project's build machine. The Rosetta datasets for 67P, Lutetia and Steins state no licence, and whether to keep them is still an open question for the owner. ## Pictures and sources Screenshots of Space Radar 1.5.1 (MIT licence) from the project's `look` workflow, probe `r15-b1`. Arrokoth's shape and albedo map: Porter (2024), New Horizons LORRI data, NASA Planetary Data System (CC0). Donaldjohanson: DLR, NASA NAIF Lucy SPICE bundle (CC0). Radar shapes: NASA 3D Resources (public domain). The shapes were prepared by Sara-Agent, the project's agent, in [pull request 1309](https://github.com/Sara-Managed-Projects/space-radar/pull/1309); every row is in [CREDITS.md](https://github.com/Sara-Managed-Projects/space-radar/blob/main/CREDITS.md). **Fly there in the 3D map:** [Fly to Arrokoth](https://www.spaceradar.ai/#go=asteroid-486958). Free, in your browser, no account. ## Sources 1. [Space Radar changelog: release 1.5.0](https://github.com/Sara-Managed-Projects/space-radar/blob/main/CHANGELOG.md) --- # Moments: a mission replayed in 3D on one clock > Release 1.5.0 adds a new kind of tour, a Moment, and its first demonstration: Apollo 11's Saturn V from ignition to the jettison of the escape tower. By Space Radar. Published 2026-10-29. Category: Missions & Spacecraft. Tags: Saturn V, Apollo 11, Moments, rockets, release 1.5. 5 min read. Canonical: https://blog.spaceradar.ai/moments-a-mission-on-one-clock/ ![The Saturn V on the pad at ignition, steam and flame thrown sideways out of the trench under it.](/media/moments-a-mission-on-one-clock/ignition.jpg) *T−00:00:04: the five F-1 engines lighting, the steam out of the flame trench drawn both ways.* Release 1.5.0 adds a new kind of tour to Space Radar, a Moment: a mission replayed in 3D on one clock, from the pad to orbit, with the camera, the stages and the flames all following the same mission time. One Moment ships with it, a 41-second demonstration of Apollo 11's Saturn V from ignition to the jettison of the escape tower. ## What a Moment is A trip on the map moves you from place to place. A Moment holds you at one place in time and lets a mission happen around you. The link `#moment=demo-saturn&t=-9.5` opens the player paused nine and a half seconds before lift-off. Press play and the five F-1 engines light, centre first, then the outboard pairs; the hold-down arms keep the stack on the pad until all five are at full thrust; it clears the tower, rolls onto its flight azimuth, 72 degrees east of north, and climbs. The clock is printed on screen the whole time, as a mission clock (`T−00:00:08`) and as a compression beside it. The first seconds play at `×1`, real time. The long climb through maximum dynamic pressure plays at `×27.5`, then the player slows to `×4` for the centre engine shutting down and to `×2` for staging, when the first stage drops away with its retro-rockets firing. Nothing is hidden about the pace: whatever is sped up says so. ![The Saturn V seen from the side 45 km up, a long white plume behind it over a blue Earth.](/media/moments-a-mission-on-one-clock/centre-engine-out.jpg) *T+00:02:17 at ×4: the centre engine is out and the plume widens in thin air, 45 km up.* ## Seven kinds of shot, and your own camera The player directs itself with seven kinds of shot: the pad, a long-lens tracking camera 1.6 km away that narrows as the rocket climbs, a chase, an orbit round the stack, an onboard view, the globe and a wide view. The Earth below is the map's own, the Sun and the Moon are where they were at 13:32 UTC on 16 July 1969, and stars appear when the sky above the rocket is dark enough. You can take the camera at any moment. Drag, scroll or pinch and the view is yours; let go and the director takes it back at the next shot. The chapters open in place above the strip, so you can jump to ignition, lift-off, maximum dynamic pressure or staging. The share button gives a link to the second you are looking at, and that link opens the player paused on the same second. ![The Moment player with its list of chapters open above the play strip.](/media/moments-a-mission-on-one-clock/chapters.jpg) *The chapters, opened in place above the strip. Each one is a second you can link to.* ## Why it was hard A rocket launch changes scale fast: metres at the pad, a hundred kilometres up and nearly two hundred downrange by the time the tower goes. The player has to keep the pad's steam, a 110-metre stack and the curve of the Earth all drawn without the numbers breaking, so the scene moves its origin with the rocket. A visitor on a phone gets the same Moment at a lower tier, and anyone who has asked the system for reduced motion gets it opened paused, with cuts in place of camera moves. None of it costs a visitor who never opens a Moment anything. The player and its files are fetched only when the link is opened; the map's first screen is unchanged. ## How to try it Open [the Saturn V Moment](https://www.spaceradar.ai/#moment=demo-saturn&t=-9.5) and press play, or use the space bar. The arrow keys step through time, `[` and `]` move between chapters, and Escape closes the player and puts the map back where it was. **Fly there in the 3D map:** [The Saturn V Moment](https://www.spaceradar.ai/#moment=demo-saturn&t=-9.5) ![The Saturn V's second stage burning over the Earth, its pale blue hydrogen flame below it.](/media/moments-a-mission-on-one-clock/second-stage.jpg) *T+00:02:54 at ×11: the five J-2 engines of the second stage; hydrogen burns pale and nearly clear.* ## Measured, reconstructed, illustrative The demonstration is honest about what it knows, and the line under the player says the same. - **Measured:** the event times come from the Apollo 11 Mission Report (NASA MSC-00171, 1969), Table 3-I: lift-off at 00:00:00.6, the outboard engines cut off at 00:02:41.7, the second stage lit at 00:02:43.0 and the tower jettisoned at 00:03:17.9. The places of the Sun and the Moon are computed for that day. - **Reconstructed:** the path between those events. The heights and the distances downrange are approximate, which is why this Moment is called a demonstration. - **Illustrative:** the flames, the steam and the ground within 25 km of the pad are drawn. In this release the stages are cut from one model of the whole rocket, and the stack stands on bare concrete because there is no model of the Mobile Launcher yet. The same release adds the vehicles for the Moments to come: the Saturn V in eleven parts in flight order, the Lunar Module in two stages and the Command and Service Module from NASA's models, SLS and Orion in named parts, and the R-7 with the Vostok capsule, its ejection seat and parachutes, built from published dimensions. The Moments of Vostok 1, Apollo 11 and Artemis II themselves are not written yet. ## Pictures and sources Screenshots of Space Radar 1.5.1 (MIT licence) from the project's `look` workflow, probe `moments`. The Saturn V is NASA's model from NASA 3D Resources (public domain), and the Earth's map is Solar System Scope's (CC BY 4.0). The player and the demonstration were built by Sara-Agent, the project's agent, in [pull request 1305](https://github.com/Sara-Managed-Projects/space-radar/pull/1305); the full rows are in [CREDITS.md](https://github.com/Sara-Managed-Projects/space-radar/blob/main/CREDITS.md). **Fly there in the 3D map:** [Watch the Saturn V Moment](https://www.spaceradar.ai/#moment=demo-saturn&t=-9.5). Free, in your browser, no account. ## Sources 1. [Space Radar changelog: release 1.5.0](https://github.com/Sara-Managed-Projects/space-radar/blob/main/CHANGELOG.md) --- # Free planetarium software for a classroom with no Wi-Fi > Nearly half the world’s schools are not online. Space Radar is built so that one of them can keep its own copy on an old laptop and teach the sky from it. How that works, what a lesson looks like, and what it honestly cannot do without a network. By Ivan Akselrot. Published 2026-10-26. Category: How It's Built. Tags: classroom, offline, planetarium software, education, present mode. 10 min read. Canonical: https://blog.spaceradar.ai/free-planetarium-software-offline-classroom/ At eight minutes past five, Universal Time, on the morning of 8 October 2026, I did something unkind to a web page. I opened Space Radar in a browser, let it settle, and cut the network. Then I pressed reload. The Earth came back, with its storms. So did the satellites, the space stations, the list of trips, the asteroid due to pass in five hours. One thing was different. The small status line at the foot of the panel, which normally counts the sources it has read, now said: “Offline: showing saved copies from a day ago.” This piece is about that line, and about the people it is for. Space Radar is free planetarium software that runs in a browser, and it is built to keep running when the network does not. I think of that as the classroom copy. ![Free planetarium software in present mode: the Moon in the upper half of the screen and, below it, large text for a room to read, headed Half, then full](/media/free-planetarium-software-offline-classroom/11-01-present-moon.jpg) *A trip in present mode, the way a class sees it: no panels, the words large enough to read from the back, one line of controls. This is stop three of “Why the Moon changes shape”.* ## Half the schools Start with who is on the other end. Giga, the programme run by UNICEF and the International Telecommunication Union to connect schools, says that [nearly half of the world’s six million schools](https://aiforgood.itu.int/speaker/giga/) are still offline. The ITU counted 2.2 billion people without the internet in 2025. Those are the dramatic cases. The ordinary one is a school that is online in the staff room and not in the room with the projector, or online until thirty children open the same page, or online behind a filter that blocks half of what a science site needs. The project’s own troubleshooting table has a row for that last one, and notes drily that it is “common behind school filters”. A planetarium, meanwhile, is a building. There were [4,267 of them in the world](https://lochnessproductions.com/reference/attendance/attendif.html) at the last count I could find, from 2020. Most children will never sit in one. So the question I care about is small and practical. Can a teacher with one middling laptop, a projector and no signal stand in front of a class and show where the Moon is tonight? The README answers in a sentence: a school, a university, a kindergarten or a village library can run its own copy, “on an old laptop, with no internet at all”. ![The Space Radar home screen running with no network: the Earth, satellites and trip list as usual, and at the foot of the panel the line Offline: showing saved copies from a day ago](/media/free-planetarium-software-offline-classroom/11-03-offline.jpg) *My test on 8 October 2026: one ordinary visit, then no network, then reload. The only visible change is the last line of the panel. The age it gives is the age of the oldest copy it is using.* ## A folder, not a service The reason this is possible is almost boring. Space Radar has no server-side program and no database. It is a folder of files. Any computer that can hand a folder to a web browser can run it, and the [guide for doing so](https://github.com/Sara-Managed-Projects/space-radar/blob/main/docs/RUN_LOCALLY.md) is addressed, in its first line, to “teachers, librarians, club leaders and anyone who is not a programmer”. What you need is modest: a computer from the last eight years or so, a browser, and Python, which most computers already have. You get the folder, type one line to serve it, and open the address it gives you. Add one option to that line and every other machine in the room can open it too. Inside the folder there are two kinds of thing, and the difference matters. The first kind never changes and ships with the app: the planets and moons and their maps, the stars, the constellations, the photographs of nebulae, every 3D model, all 26 guided trips with their narration, and the mathematics that moves it all. That part needs no network, ever. The planets and the Moon are computed, not downloaded, so they are right for any date. The second kind changes daily: the list of satellites and their orbits, the launches, the passing asteroids, the space weather. For these the app keeps a saved copy and reads it first. One short script fills that copy while you are online. It downloads about 24 megabytes from the project’s own site and, in the words of its documentation, “contacts nobody else”. - **110 MB** is the whole thing on disk, the saved data included. About 40 of those megabytes are the trips’ narration and music. There is a second route, which is the one I tested. Visit the live site once, and a small program the browser keeps, a [service worker](https://developer.mozilla.org/en-US/docs/Web/API/Service_Worker_API), holds on to the app and to the maps, models and sounds you used. Next time it starts with the cable out. It keeps only what that browser has actually seen, so the documentation gives the one piece of advice a teacher needs: to have a trip ready for a room with no network, play it through once on that computer first. ## What a lesson looks like Pick a trip and press Present, or add `present=1` to its link. The panels go. The words of each stop are set large. The trip waits. From there a presenter’s clicker is the whole interface, because a clicker sends the arrow keys. Right for the next stop, left for the one before, F for full screen. The words on the screen are the captions, so the room does not need loudspeakers. If you do have sound, a voice reads each stop and the trip waits for it to finish. The guide suggests where to begin: [why the Moon changes shape](https://www.spaceradar.ai/#trip=moon-phases&present=1), the planets tonight, [the Sun today](https://www.spaceradar.ai/#trip=the-sun-today), Mars, [the constellations](https://www.spaceradar.ai/#trip=the-constellations&present=1), the life of a star. Six of the trips start from your own place, so there is one thing to do before the bell: tell it the school’s town. Otherwise it guesses from the computer’s clock, and says that it guessed. **Fly there in the 3D map:** [Why the Moon changes shape](https://www.spaceradar.ai/#trip=moon-phases&present=1) ![A trip stop about the Plough: the stars of the Great Bear and the Little Bear joined by lines, with Polaris labelled, and a card explaining how to find north](/media/free-planetarium-software-offline-classroom/11-04-plough.jpg) *Stop six of twelve in the constellations trip: two stars at the end of the bowl, followed five times their own gap, point at Polaris. The card’s last line says the figures are “a tradition, drawn by us”.* ![The surface of the Sun filling the screen in orange, with a card titled Spots, and an eleven-year beat](/media/free-planetarium-software-offline-classroom/11-06-sunspots.jpg) *From “The Sun today”. Online, this stop shows today’s numbered sunspot groups; offline it cannot, and the list below says so.* ## The honest list Here is where a brochure would stop, and where the project’s documentation gets interesting. It has a table with two columns: “Works with no internet” and “Needs the internet”. It was filled in by measurement, by serving the folder with every outside address blocked and writing down what happened. What works: the Earth, the Moon, every planet and moon with their maps; the stars, the Milky Way, the nebula photographs; all the trips with narration and captions; the satellites and both space stations, from the saved copy; search, the time scrubber, tonight’s passes; present mode; the sky from a city you pick by hand. What does not: today’s clouds, storms and lightning, for which you get a fixed cloud map; the close-up tiles of the Earth, the Moon and Mars; fresh launches and space weather; the maps of sea temperature and rain; your exact location on some machines. And then the paragraph that I think every piece of classroom software should be made to carry: > Be honest with your class about age. A satellite’s position is worked out from numbers measured on a certain day. The saved copy is as old as the day it was made, and every card says so at its foot. After a week or two, the guide warns, a low satellite such as the space station “can be minutes away from where the app draws it”. Refresh the copy when you can. Tell the children when you cannot. It is a better lesson about data than most of them will get that year. ## No accounts, and why that is a school feature In 2022 Human Rights Watch examined 163 education products that governments had endorsed for children during the pandemic. It found that [145 of them, 89 percent](https://www.hrw.org/report/2022/05/25/how-dare-they-peep-my-private-life/childrens-rights-violations-governments), put children’s rights at risk or infringed them outright. A copy of Space Radar on a school laptop cannot do that, and not because of a policy. There are no accounts to create. There is nothing to send, and when the network is unplugged, nowhere to send it. The project’s design rules put it in five words, “Nobody is tracked”, but the stronger guarantee is the cable lying on the desk. The same holds for a class website. One live object or one trip can be put into any page as [an embedded frame](https://www.spaceradar.ai/?embed=1&at=sat-25544), and the [embedding notes](https://github.com/Sara-Managed-Projects/space-radar/blob/main/docs/EMBEDDING.md) are specific about what a reader gets: the scene, the object’s name and two numbers, one link back. “Nothing is stored on the reader’s device by the embed: no cookie, no tracker.” ![An embedded frame of the Earth seen close up over Arabia and North Africa, with a small tag for the International Space Station giving its height, speed and the age of its elements](/media/free-planetarium-software-offline-classroom/11-02-embed.jpg) *The embed: the space station over North Africa on 8 October 2026, with its tag and one link, “Open in Space Radar”. No sidebar, no search, no clock.* ## What I would tell a teacher Three cautions, since this is a piece about honesty. The interface, the cards and the voice are in English only. For many classrooms that is the largest obstacle on this page, and for now the teacher is the translator. Pupils’ own machines are a special case. Browsers allow a page to keep itself for offline use only when it comes from a secure address or from the computer itself. Thirty tablets reading from the teacher’s laptop will need that laptop running. In the guide’s words, that is “the browser’s rule, not ours”. And the ready-made download that the guide describes, a single zip that starts offline, had not yet been published when I wrote this. The route that works today is to copy the repository and run the save script once, or simply to visit the site on the classroom computer while it has a connection. None of this is new as an idea. [Kiwix](https://kiwix.org/en/) has carried Wikipedia into places without the internet for years. What I wanted was the same stubbornness for the sky: a planetarium that a school owns the way it owns a globe. So try the unkind test yourself. Open [the map](https://www.spaceradar.ai/) on the computer you teach from. Play one trip through. Then pull the cable, reload, and read the last line of the panel. > **About Space Radar.** Space Radar is a free, open-source live 3D map of everything in orbit and beyond, built to run in a classroom with no internet. It is at [spaceradar.ai](https://www.spaceradar.ai/), with no account; the code and the classroom guide are on [GitHub](https://github.com/Sara-Managed-Projects/space-radar). **Fly there in the 3D map:** [Moon phases, in present mode](https://www.spaceradar.ai/#trip=moon-phases&present=1). Free, in your browser, no account. ## Questions people ask ### Is there free planetarium software that works offline? Yes. Space Radar runs from a folder on an ordinary computer with no internet, or from the browser after one online visit. Stellarium is another free, open-source option, installed as a desktop program. ### What does a school need to run it? A computer from the last eight years or so, a web browser and Python 3. No account, licence key or build tool is involved; the whole copy is about 110 MB. ### What stops working without the internet? Anything that is today’s news: live clouds, fresh launches and space weather, close-up map tiles. Planets, stars, eclipses and the guided trips are unaffected; satellites are drawn from a saved copy that states its age. ### Does it collect pupils’ data? No. There are no accounts, no analytics cookies and no personal data in any request. A copy running with the network unplugged has nowhere to send anything. ## Sources 1. [GitHub](https://github.com/Sara-Managed-Projects/space-radar) 2. [Nearly half of the world’s six million schools](https://aiforgood.itu.int/speaker/giga/) 3. [4,267 of them in the world](https://lochnessproductions.com/reference/attendance/attendif.html) 4. [Service worker](https://developer.mozilla.org/en-US/docs/Web/API/Service_Worker_API) 5. [145 of them, 89 percent](https://www.hrw.org/report/2022/05/25/how-dare-they-peep-my-private-life/childrens-rights-violations-governments) 6. [Kiwix](https://kiwix.org/en/) 7. [Spaceradar.ai](https://www.spaceradar.ai) 8. [Giga.global](https://giga.global/) 9. [Itu.int: PR 2025 11 17 Facts and Figures.aspx](https://www.itu.int/en/mediacentre/Pages/PR-2025-11-17-Facts-and-Figures.aspx) 10. [Kiwix.org: about us](https://kiwix.org/en/about-us/) 11. [Stellarium.org](https://stellarium.org/) --- # A solar eclipse simulator, and a clock you can drag > Drag the clock on a map of space and the Moon’s shadow, the seasons and the planets all move to where they will be. The satellites move too, and the map tells you to trust those less. On honest time travel. By Ivan Akselrot. Published 2026-10-24. Category: Solar System. Tags: time machine, eclipse simulator, Moon phases, orbits, accuracy. 9 min read. Canonical: https://blog.spaceradar.ai/solar-eclipse-simulator-time-machine/ In March 1715 a sheet of paper went on sale in London showing England with a dark oval lying across it. The astronomer Edmond Halley had worked out where the shadow of the Moon would fall on the morning of 3 May, and he had it printed weeks beforehand. The eclipse came, and London had three and a half minutes of night. By the usual account his timing was out by about four minutes, and his path by about twenty miles. That sheet was a solar eclipse simulator made of ink. What made it possible is still the strangest fact about the sky: the big things in it keep their appointments. Know where the Sun and the Moon are, and you know where the shadow goes, three centuries ago or three centuries on. I work on Space Radar, a live map of space, and at the bottom of its screen there is a clock you can drag. This piece is about what happens when you do. Most of what is on the map obeys. Some of it only pretends to, and the interesting part is that the map tells you which. ![A solar eclipse simulator view of the Earth during the ring eclipse of 6 February 2027, seen over South America and the Atlantic, with a card titled A ring, not a night](/media/solar-eclipse-simulator-time-machine/10-04-ring-eclipse.jpg) *The next solar eclipse after this article, 6 February 2027, a ring and not a total one. The card’s small print: “Shadow computed from the Moon’s and the Sun’s positions; timing from Astronomy Engine, to about a minute.”* ## A tape, not a slider The clock is a pill at the foot of the picture. Left alone it reads LIVE and the time. Above it is a strip of ticks, and the strip is the thing you move: time is a tape that slides under a fixed mark, the way a station slides under the needle of an old radio. The reason is in the code, in a comment: the things worth going to are a satellite pass in forty minutes and an eclipse in ten months, and on one fixed track “the next pass is a pixel from now”. So the tape has three gears, a minute, an hour or a day to the tick, and a speed button that runs the clock at up to an hour a second. On the tape there are marks. The next pass over your place. A launch. An asteroid going by. The peak of a meteor shower. The Moon’s four phases. Tap a mark and the clock goes there. The tape reaches a month back and a year on. Another comment in the code says why it has the place a video player gives its own: > Time is not a setting; it is the one control a map of things in motion is about. ![The Space Radar home screen with the time bar at the bottom set to days: tick marks, small marks for coming events, and hatched stretches labelled rougher](/media/solar-eclipse-simulator-time-machine/10-03-tape.jpg) *The tape in its widest gear, a day to the tick. The small shapes are events you can jump to. The hatching, and the word “rougher”, are the subject of the last part of this piece.* ## The line that never stops The simplest thing to watch is the edge of night. Half the Earth is always in daylight, and the line between the halves sweeps westward over the ground as the planet turns, at the equator at about [1,675 kilometres an hour](https://gpm.nasa.gov/education/articles/orbits-r-us). Drag the tape by hand and you can pull dusk across a continent and watch the cities switch on behind it. Then go further. One of the trips, [the living Earth](https://www.spaceradar.ai/#trip=the-living-earth), sets the clock to 21 June and then to 22 December and stops at each. In June the line between day and night crosses the map at a slant, and the Arctic never gets dark. Six months on it leans the other way. The card says what you are looking at: the Earth is tipped over by twenty-three degrees and keeps leaning the same way all year. “That lean, and nothing else, makes the seasons.” **Fly there in the 3D map:** [The living Earth](https://www.spaceradar.ai/#trip=the-living-earth) ![The Earth with Africa, Arabia and Europe in daylight and the line of night running at a slant, as on 21 June](/media/solar-eclipse-simulator-time-machine/10-01-june-solstice.jpg) *21 June 2027: the north is tipped towards the Sun. Nothing in this picture is stored; the lit half is worked out from where the Sun is at that instant.* ![The Earth with the Americas half in night, the line between day and night slanting the opposite way, as on 22 December](/media/solar-eclipse-simulator-time-machine/10-02-december-solstice.jpg) *22 December 2027, half an orbit later. The Sun sends the same energy as before; the tilt decides who gets it.* ## Eclipses, to the minute Halley needed weeks of work with tables. The map does it while you watch, with the same ingredients: where the Sun is, where the Moon is, and a line through both. The Moon’s shadow on the Earth is not a stored animation. It is drawn from the two positions at the instant on the clock, so it is right for any eclipse you can scrub to. The trip called “Chasing the solar eclipse” takes the clock to the next few. After the ring of February 2027 comes the one people are already booking flights for: 2 August 2027, a total eclipse whose shadow crosses southern Spain, North Africa and Arabia, with up to [6 minutes 23 seconds of totality](https://eclipse.gsfc.nasa.gov/SEgoogle/SEgoogle2001/SE2027Aug02Tgoogle.html), according to NASA. You can stand above the Earth at [the minute it happens](https://www.spaceradar.ai/#trip=chasing-the-solar-eclipse&stop=2) and watch the dark core cross the ground. The last stop turns the arrangement round. Now the Earth is in the way, and [the Moon slides into our shadow](https://www.spaceradar.ai/#trip=chasing-the-solar-eclipse&stop=5). The next total one the map finds is on 31 December 2028, which is a fine thing to know two years early. **Fly there in the 3D map:** [The Moon slides into our shadow](https://www.spaceradar.ai/#trip=chasing-the-solar-eclipse&stop=5) Why can a web page do this for dates so far off? Because the motions of the Sun, the Moon and the planets are known very well indeed. The reference tables that NASA’s Jet Propulsion Laboratory publishes for them [run from the year 1549 to 2650](https://ssd.jpl.nasa.gov/planets/eph_export.html). The map does these sums with an open-source library, [Astronomy Engine](https://github.com/cosinekitty/astronomy). The tape says it in six words: “Planets and moons hold for centuries.” ## A year in a minute Speed is the other half of a time machine. One trip runs the clock 525,600 times too fast, which is exactly [a year in a minute](https://www.spaceradar.ai/#trip=a-year-in-a-minute). Every second is six days. Mercury laps the Sun in fifteen seconds. The Moon goes round the Earth in four and a half. It teaches something that no still diagram can. The planets do not go round like horses on a carousel. The inner ones overtake, again and again, and the outer ones barely seem to try: in the minute it takes the Earth to go round once, Jupiter covers a twelfth of its path. ![The Sun at the centre of four orbit rings with small dots for Mercury, Venus, the Earth and Mars, and a card titled Everything inside Mars, going round](/media/solar-eclipse-simulator-time-machine/10-06-year-in-a-minute.jpg) *The inner Solar System with the clock running a year a minute. The card’s caveat: the planets are dots “drawn far larger than they are”, each on the path it really follows.* ## Backwards, to a Sunday evening in 1969 The tape itself goes back only a month. Some things go back much further, because they are links to a moment. More than a dozen missions have a timeline on their card, each event with its date and its source. Choose one and the clock goes there. So you can open [the Moon at 20:17 UTC on 20 July 1969](https://www.spaceradar.ai/#event=apollo-11.landing), the minute the Eagle landed. The time pill reads “57 years ago”. The lander is where it is. What the map has worked out afresh is the light: the Moon is lit as it was that day. **Fly there in the 3D map:** [The Moon at 20:17 UTC on 20 July 1969](https://www.spaceradar.ai/#event=apollo-11.landing) ![The Apollo 11 lunar module on the Moon, and a card showing the event The Eagle has landed, 20 July 1969, 20:17 UTC](/media/solar-eclipse-simulator-time-machine/10-07-apollo-event.jpg) *20 July 1969, 20:17 UTC. Under the event the card says “The clock is at this moment. Live brings it back.”* Here the honesty gets specific. For a spacecraft that was moving, the map needs a record of its path on that date, and often it has none. Then it says so and does not move the clock at all. I came across this by accident on the space station’s own card, on an event from 2011: “The map has no path for International Space Station on that day, so the clock stays where it is.” ## Where the time machine stops being honest Which brings us to the hatching on the tape. A week either side of now, the strip is shaded and marked “rougher”, and if you ask why, it answers: “Satellite places are rough this far from now.” A satellite is not a planet. It ploughs through the thin top of the atmosphere, which swells and shrinks with the Sun’s mood, and its operators fire its thrusters without telling a web page. The published numbers for its orbit are a fit to recent tracking, good to something like a kilometre near the day they were made and worse with every day after. So the map calls a satellite’s place “measured” only within twelve hours of that day. Beyond a month, it stops drawing the satellite at all. ![The time bar moved sixteen days ahead, with the tape hatched and labelled rougher and the Earth with satellites above it](/media/solar-eclipse-simulator-time-machine/10-09-rougher.jpg) *The clock sixteen days ahead. The Earth, the Sun’s light and the Moon are right for that date. The satellites are where old numbers say they would be, and the hatching is the map saying so.* The same goes for the weather. Scrub more than half a day from the latest satellite picture and the clouds on the globe become a stand-in, and a line says they are “illustrative”. A launch on the tape is a plan, and reads “give or take” when the date is not fixed. I find this the most satisfying part of the whole thing. A time machine that moved everything with equal confidence would be easier to build and nicer to demo. It would also be lying about half of what it showed. One last appointment, then. On 13 April 2029 an asteroid about 340 metres across, Apophis, will pass some 32,000 kilometres above the ground, inside the ring of television satellites. The map will [take you to that evening](https://www.spaceradar.ai/#trip=asteroids-that-come-close&stop=7) today. The card under it is three words long where it matters: “It will miss.” Then press Live, and come back to now. > **About Space Radar.** Space Radar is a free, open-source live 3D map of everything in orbit and beyond, with a clock you can drag. It runs in a browser at [spaceradar.ai](https://www.spaceradar.ai/), with no account; the code is on [GitHub](https://github.com/Sara-Managed-Projects/space-radar). **Fly there in the 3D map:** [A year in a minute](https://www.spaceradar.ai/#trip=a-year-in-a-minute). Free, in your browser, no account. ## Questions people ask ### Is there a free solar eclipse simulator online? Yes. Space Radar draws the Moon’s shadow on the Earth for any eclipse its clock can reach, computed from the Sun’s and Moon’s positions, in a browser with no account. NASA also publishes interactive path maps for each eclipse. ### How accurately can an eclipse be predicted? Very. The motions of the Sun and Moon are known well enough that eclipse times are given to the second decades ahead; the map’s own timing is good to about a minute. ### Can I see where a satellite will be next month? Only roughly. Published orbits are fits to recent tracking and drift within days, so the map marks satellite positions more than a week from now as “rougher”. ### Can I go back in time on the map? The timeline reaches a month back and a year forward, and links can open other moments, such as the Apollo 11 landing. Planets and moons are computed for any date. ## Sources 1. [GitHub](https://github.com/Sara-Managed-Projects/space-radar) 2. [1,675 kilometres an hour](https://gpm.nasa.gov/education/articles/orbits-r-us) 3. [6 minutes 23 seconds of totality](https://eclipse.gsfc.nasa.gov/SEgoogle/SEgoogle2001/SE2027Aug02Tgoogle.html) 4. [Run from the year 1549 to 2650](https://ssd.jpl.nasa.gov/planets/eph_export.html) 5. [Astronomy Engine](https://github.com/cosinekitty/astronomy) 6. [Spaceradar.ai](https://www.spaceradar.ai) 7. [En.wikipedia.org: Solar eclipse of May 3, 1715](https://en.wikipedia.org/wiki/Solar_eclipse_of_May_3,_1715) 8. [Eclipse.gsfc.nasa.gov: SEdecade2021](https://eclipse.gsfc.nasa.gov/SEdecade/SEdecade2021.html) 9. [Arxiv.org: 1002.2277](https://arxiv.org/abs/1002.2277) --- # A virtual space tour that begins with a family photo > A map with a legend tells you everything at once. A guide tells you one thing, then the next. On the 26 narrated trips in Space Radar, how they are written, and three of them retold. By Ivan Akselrot. Published 2026-10-22. Category: How It's Built. Tags: guided trips, narration, education, 3D map, astronomy. 10 min read. Canonical: https://blog.spaceradar.ai/virtual-space-tour-narrated-trips/ In April 1972 an astronaut called Charlie Duke walked a little way from his lunar module and left a photograph of his family lying on the ground. They had signed the back and pressed their thumbprints into it. Under the signatures it says: “This is the family of Astronaut Duke from Planet Earth, who landed on the Moon on the twentieth of April 1972.” It is still there. Nobody has been back to look at it, and its exact spot has never been surveyed. But the lander it lies beside has been located to within three metres, and you can go and stand over the spot. That is how one virtual space tour I know begins. It is the first stop of a trip called “The strangest things we have ever sent”, one of 26 guided, narrated journeys in Space Radar, the live map of space I work on. This piece is about why the map teaches that way. A legend can tell you what the orange dots are. It takes a guide to make you care about one of them. ![A virtual space tour stop on the Moon: a grey lunar surface with the Apollo 16 lander, a pale marker where a photograph lies, and a card titled A photograph lying in the dust](/media/virtual-space-tour-narrated-trips/08-02-duke-photo.jpg) *Stop one of six. The card’s small print is careful: the lunar module’s position is measured to three metres, and the photograph itself “has never been surveyed”.* ## The oldest trick in the dome On 7 May 1925 the Deutsches Museum in Munich [opened a room to the public](https://www.deutsches-museum.de/en/museum-island/programme/programme-a-z/planetarium/history-of-the-planetarium) in which a machine by Carl Zeiss threw about 4,500 stars onto the inside of a dome. The machine was the wonder. What made it a lesson was the person standing beside it in the dark with a pointer, deciding where a roomful of people looked, and in what order. That is the trick. A sky, or a map of everything in orbit, gives you all of it at once, and a beginner faced with all of it sees none of it. A guide removes almost everything. Look here. Now here. Now turn round. So Space Radar has trips. A trip is a chain of stops. At each one the camera flies to a real place, a short card appears, and a voice reads it. There are 205 stops across the 26 trips, and a little over an hour of narration in all. The shortest take a minute. None takes more than five. ![The Space Radar home screen with a list of trip cards down the left side: Where people are living in space right now, The living Earth, Why the Moon changes shape, A dark sky and others](/media/virtual-space-tour-narrated-trips/08-01-trip-list.jpg) *Some of the 26. A trip that cannot run today is greyed with its reason and never hidden; the two dated ones show when their event next happens.* ## Six things we left out there Back to the strange things. From Duke’s photograph the camera lifts and crosses to another part of the Moon, where in 1971 Alan Shepard hit two golf balls with a six-iron head fixed to a sampling tool. The card corrects a legend in passing: they went “twenty-four and forty yards, not the miles everybody repeats”. Third stop: the wreck of Beresheet, the Israeli lander that hit the Moon in 2019 carrying a disc library of thirty million pages and some dried tardigrades. Nobody knows where in the wreck the discs ended up, the card says, or whether the tardigrades survived. Then the camera leaves the Moon altogether and goes a very long way, to Voyager 1 and [the gold record bolted to its side](https://www.spaceradar.ai/#trip=strangest-things&stop=4). The card picks three things from [what is on that record](https://science.nasa.gov/mission/voyager/golden-record-contents/): whale song, greetings in fifty-five languages, “and one woman’s heartbeat, recorded two days after she decided to get married”. **Fly there in the 3D map:** [The gold record bolted to its side](https://www.spaceradar.ai/#trip=strangest-things&stop=4) ![The Voyager 1 spacecraft against black space with a card titled A gold record, further away than anything, giving 172 AU from Earth and 17 930 days in space](/media/virtual-space-tour-narrated-trips/08-03-golden-record.jpg) *Voyager 1 on 8 October 2026: 172 times as far from us as the Sun is, and 17,930 days out. Its position is “worked out rather than measured”, which is the map’s way of saying nobody can see it.* After that, a car going round the Sun with a towel in its glovebox. And then the stop the whole trip was built for: the camera pulls back until the Earth is a point. “Every one of those things was made by people standing on that. From out here you cannot pick it out of the dark.” Six stops, about two minutes, and not one of them is a lesson in orbital mechanics. But at the end of it you know that the Moon has places, that Voyager is far in a way you can feel, and that all of it started in one spot. A table could not have done that. ## Why the Moon changes shape, in seven stops The second trip I want to retell is the one I would show a class first. Ask [why the Moon changes shape](https://www.spaceradar.ai/#trip=moon-phases) and the tempting answer is the Earth’s shadow. It is a reasonable guess, and it is wrong; one of the stops is named for the mistake. The trip does not say so straight away. It takes you far above the north pole and shows the Moon’s whole path as a ring, with the Sun off to one side lighting the same half of both worlds, all the time. Then it drops you to where the Earth is and runs the clock at ten hours a second. A thin edge of light appears on the Moon and grows. Nothing is covering it. You are simply seeing more of its day side each evening as it moves round. ![The Earth as a small blue point at the centre of a thin ring that marks the Moon's path, with the Moon as a small dot on the ring](/media/virtual-space-tour-narrated-trips/08-04-moon-month.jpg) *The Moon’s month from above the north pole, on a date in January 2027. The ring is thirty Earths out. Both worlds are drawn larger than they are, and the card says so.* Only at stop six does the shadow come in. The clock jumps to the next total lunar eclipse and the Earth’s shadow really does slide across the Moon. Now you can see that it looks nothing like a phase, and the card explains why it is rare: the Moon’s path is tilted five degrees against ours, so at most full Moons it passes above or below the shadow. The last stop puts you on your own street, tonight, with the Moon where it is for you. “Look again tomorrow at the same hour.” ![The Moon as a thin lit crescent on its right edge, with a card titled A sliver that grows](/media/virtual-space-tour-narrated-trips/08-05-moon-sliver.jpg) *Stop two, a couple of days after a new Moon. The trip runs the clock at ten hours a second here; the line under the title always says what moment is shown.* > A trip may not promise a stop it will not deliver. ## How a trip is written That sentence is from the top of the file where all 26 trips live, and it is the one rule the rest come from. A trip is not a film. It is a few dozen lines of plain text in [a file anyone can read](https://github.com/Sara-Managed-Projects/space-radar/blob/main/registry/tours.yaml), and each stop names exactly one real target: an object, a world, a landing site, a patch of sky, or the visitor’s own place. If the target cannot be found on the day, because a satellite has come down or a source could not be read, the stop is dropped before the count is shown. “Five stops, about two minutes” has to be a true sentence. The other rules are about honesty and about the ear. Every number and name on a card needs a source, written in a comment above the trip. A card may not call a model or a false-colour map a photograph. A card may not state the time itself; the frame prints “Shown at” from the clock, so the words cannot drift from the picture. And the words are written to be heard: short sentences, plain words, for a curious twelve-year-old. The voice is [synthetic](https://huggingface.co/hexgrad/Kokoro-82M), and the app says so on the button that turns it on. It was slowed to four fifths of its natural speed, about 155 words a minute, with a note in the file that I am fond of: “a planetarium is not in a hurry”. The script that makes the audio refuses any number it does not know how to pronounce. Every clip is then played to a speech recogniser, to catch a name said wrong. I should be honest about the limit of that. A machine has heard every clip. As I write, an open issue in the project’s tracker says that no person has yet sat and listened to all of it. ## The life of a star, told with nine real ones The third trip is the one that shows what the method is for. Nobody can watch a star live; it takes millions or billions of years. But the sky holds stars of every age at once, and [the trip visits one real star at each stage](https://www.spaceradar.ai/#trip=life-of-a-star), in order, like a family album assembled from strangers. **Fly there in the 3D map:** [The trip visits one real star at each stage](https://www.spaceradar.ai/#trip=life-of-a-star) It starts in the Orion Nebula, where stars are being made now. Then the Pleiades, about a hundred million years old, “which for a star is childhood”. Then our own Sun, a little under half way through. Arcturus, which is what the Sun will become. Betelgeuse, heavy, young and already near its end. The Helix Nebula, a star like ours letting go of its outer layers. And then the other ending. In the year 1054, the card says, Chinese astronomers recorded a new star that could be seen in daylight for nearly a month. The camera is already flying to where it was. [What is there today is the Crab Nebula](https://www.spaceradar.ai/#trip=life-of-a-star&stop=8), and at its centre a ball twenty kilometres across, spinning thirty times a second. ![The Crab Nebula, a tangle of orange filaments around a blue glow, with a card titled A star that blew up and a photo credit line](/media/virtual-space-tour-narrated-trips/08-06-crab.jpg) *The wreck of the star of 1054. Under the text the card names who took the picture and what was done to it: “edges faded and sky darkened by us”.* ## In a room, with a clicker A trip on a phone is a private thing. The same trip can be given to a room. Add one word to its link, or press Present on its first card, and the panels go, the words of each stop are set large enough to read from the back, and whoever holds the clicker decides when to move on. The words on screen are the captions, so the room does not need sound. A teacher can open [the Mars trip, ready to present](https://www.spaceradar.ai/#trip=mars-where-we-have-driven&present=1), and be the person with the pointer. ![A trip in present mode: Mars filling the upper half of the screen and large text below it for a room to read](/media/virtual-space-tour-narrated-trips/08-08-present.jpg) *Present mode. No sidebar, no search, one line of controls. The arrow keys, which is what a presenter’s clicker sends, move between stops.* That, in the end, is all a trip is: somebody chose where you should look first. Tonight, take the two-minute one. [Start with the photograph in the dust](https://www.spaceradar.ai/#trip=strangest-things), let it carry you out past the planets, and wait for the last stop, when the camera turns round. **Fly there in the 3D map:** [Start with the photograph in the dust](https://www.spaceradar.ai/#trip=strangest-things) > **About Space Radar.** Space Radar is a free, open-source live 3D map of everything in orbit and beyond, with 26 narrated trips. It runs in a browser at [spaceradar.ai](https://www.spaceradar.ai/), with no account; the code is on [GitHub](https://github.com/Sara-Managed-Projects/space-radar). **Fly there in the 3D map:** [Take a trip: the life of a star](https://www.spaceradar.ai/#trip=life-of-a-star). Free, in your browser, no account. ## Questions people ask ### Is there a free virtual space tour I can take online? Yes. Space Radar has 26 guided trips that run in a browser with no account, each a few minutes long, with narration and captions. NASA’s Eyes and several museums offer tours of their own as well. ### How long does a trip take? Between one and five minutes. Each trip’s card shows its number of stops and its length before you start, and you can pause, go back or leave at any stop. ### Is the narration a real person? No. It is a synthetic voice made in advance from the words on the cards, and the app says so. Captions carry the same words, so a trip works with the sound off. ### Can I show a trip to a class? Yes. Present mode sets the words large, hides the panels and waits for a clicker or the arrow keys. It also works from a copy saved on the school’s own computer. ## Sources 1. [GitHub](https://github.com/Sara-Managed-Projects/space-radar) 2. [Opened a room to the public](https://www.deutsches-museum.de/en/museum-island/programme/programme-a-z/planetarium/history-of-the-planetarium) 3. [What is on that record](https://science.nasa.gov/mission/voyager/golden-record-contents/) 4. [Synthetic](https://huggingface.co/hexgrad/Kokoro-82M) 5. [Spaceradar.ai](https://www.spaceradar.ai) 6. [Spectrum.ieee.org: planetarium history](https://spectrum.ieee.org/planetarium-history) --- # What Is in the Sky Tonight? Relearning to Look Up > What is in the sky tonight, seen from an ordinary city balcony, is a short list. Almost nobody is taught it any more. It takes one evening to learn. By Ivan Akselrot. Published 2026-10-20. Category: Skywatching. Tags: stargazing, night sky, light pollution, planets, constellations. 11 min read. Canonical: https://blog.spaceradar.ai/what-is-in-the-sky-tonight/ At 4:31 on the morning of 17 January 1994, an earthquake of magnitude 6.7 threw Los Angeles out of bed and switched it off. The power failed across the city. People stood in the street in the dark, waiting for the next aftershock, and some of them looked up. Then the phones began to ring at Griffith Observatory, on its hill above Hollywood. The callers wanted to know why the sky looked so strange, and whether it had something to do with the earthquake. Ed Krupp, the observatory’s director, has told the story ever since. Nothing was wrong with the sky. With the lights out, the people of Los Angeles were seeing the stars, and they did not recognise them. This piece is about what those callers had lost, and about how little it takes to get a working part of it back. Most people alive have never seen the Milky Way from the place where they live. But the question people really type into a search box, *what is in the sky tonight*, has a short answer even from a balcony in the middle of a city, and it can be learned in an evening. I spent mine with [Space Radar](https://www.spaceradar.ai/), a free live map of the sky and of everything in orbit, set to a balcony in Tel Aviv on a moonless night in October 2026. ![The evening sky over Tel Aviv on 12 October 2026 with Saturn above the eastern horizon and the constellation figures drawn in](/media/what-is-in-the-sky-tonight/04-01-evening-sky-tel-aviv.jpg) *Tel Aviv, 12 October 2026, 20:45, looking east-south-east. The one bright point in this whole stretch of sky is not a star: it is Saturn, 1.3 billion kilometres away.* ## The street lamp that erased the Milky Way In 2016 a team led by the Italian physicist Fabio Falchi published [a world atlas of artificial night-sky brightness](https://www.science.org/doi/10.1126/sciadv.1600377): satellite data on the light we send upwards, checked against sky-brightness measurements taken from the ground. Its numbers are still the ones everybody quotes. More than 80 per cent of humanity lives under a light-polluted sky. The Milky Way, our own galaxy seen edge-on from the inside, is hidden from more than a third of the people on Earth, including 60 per cent of Europeans and nearly 80 per cent of North Americans. The mechanism is ordinary. A street lamp, a billboard, a floodlit car park each send part of their light sideways and upwards. The air scatters it, and the sky over a town glows like a dimly lit ceiling. The stars do not go out. They are outshone, the way a candle is outshone when somebody switches on the main light. ![The night side of the Earth from space, with Europe, North Africa and the Middle East picked out in city lights](/media/what-is-in-the-sky-tonight/04-05-earth-at-night.jpg) *Every glow here is a town, and the part of its light that reaches orbit is light that lit nothing on the ground. This is what the atlas measures.* And the ceiling is getting brighter. In 2023 Christopher Kyba and his colleagues [analysed 51,351 observations](https://noirlab.edu/public/news/noirlab2302/) sent in between 2011 and 2022 by volunteers who simply went outside and compared the stars they could see with a set of charts. The stars were vanishing at a rate that matches a sky brightening by 7 to 10 per cent every year, far faster than satellites had suggested. Kyba put it in terms of one childhood. - **250 → 100** A child born where 250 stars are visible would see only about 100 of them from the same spot by the age of eighteen. You can watch the effect without leaving your chair. The two pictures below are the same patch of south-western sky over Tel Aviv at the same minute, drawn first as a city centre shows it and then as it looks from a dark place. Nothing was added to the second one. It is what the first one is hiding. To do the same for your own town, [see your sky from a city, a town’s edge and a dark place](https://www.spaceradar.ai/#trip=a-dark-sky&stop=3). **Fly there in the 3D map:** [See your sky from a city, a town’s edge and a dark place](https://www.spaceradar.ai/#trip=a-dark-sky&stop=3) ![The south-western sky from a city centre above a skyline: an orange glow along the horizon and only two bright stars, Vega and Altair, with the constellation figures drawn in](/media/what-is-in-the-sky-tonight/04-03-city-sky.jpg) *From the city centre. The constellation lines are drawn by the map; the sky itself offers Vega, Altair and very little else.* ![The same south-western sky from a dark place: thousands of stars and the glow of the Lagoon Nebula in Sagittarius](/media/what-is-in-the-sky-tonight/04-04-dark-sky.jpg) *The same sky, the same minute, from a dark place. The stars lie thickest along the Milky Way, which runs from Vega and Altair down to Sagittarius on the horizon.* ## What survives the glow is a short list Here is the consolation. The brightest things in the sky are bright enough to beat any street lamp, and there are few enough of them to learn by name. From a truly dark site the unaided eye can pick out roughly 2,500 stars at one time. From the centre of a large city the count falls to [a dozen or two](https://coolcosmos.ipac.caltech.edu/ask/206-How-many-stars-can-you-see-at-night-). That sounds like a loss, and it is, but it is also a gift to a beginner: the city has deleted everything except the landmarks. The first landmarks are the planets. Five of them can be seen without a telescope, and on a given night some of those are up and some are not. The trick for telling a planet from a star is old and reliable: stars twinkle and planets, mostly, do not. A star is so far away that its light arrives as a single point, which moving air pushes about. A planet is a tiny disc, and a disc holds steady. > The city has deleted everything except the landmarks. The second trick is that the planets all keep to one line across the sky, the same path the Sun took during the day. Find one and the others are somewhere along it. ![Space Radar’s Tonight panel for Tel Aviv, listing the next satellite pass and the night’s brightest sights with their magnitudes, beside the evening sky with Saturn labelled](/media/what-is-in-the-sky-tonight/04-02-tonight-panel.jpg) *The map’s answer for one balcony on one night: the next satellite pass, then the night’s best by brightness. Magnitude runs backwards: the lower the number, the brighter the object, so Jupiter at −1.9 outshines every star in the sky.* On my October evening the map’s answer for Tel Aviv was three planets. Saturn was already climbing in the east as the sky went dark, and would stand highest, 60 degrees up in the south, a few minutes before midnight. Jupiter and Mars would not rise until the small hours and were best just before dawn. The Moon, a two-day-old sliver, had set before the sky was dark. That list changes week by week, which is why it is worth asking again: [see which planets are up tonight](https://www.spaceradar.ai/#trip=planets-tonight), each in turn and then from your own street. **Fly there in the 3D map:** [See which planets are up tonight](https://www.spaceradar.ai/#trip=planets-tonight) ![Saturn and its rings seen from close by, lit from the side, with stars behind](/media/what-is-in-the-sky-tonight/04-08-saturn.jpg) *What that steady yellowish point is. The rings reach 80,000 kilometres out from the planet and are in places only about ten metres thick; a small telescope shows them.* ## Four minutes of people One light in the evening sky behaves like nothing else. It appears low in the west, steady and white, with no flashing lights. It crosses the whole sky in a few minutes and then, often, fades out in mid-air before it reaches the far horizon. That is the International Space Station, and [it can be followed live](https://www.spaceradar.ai/#at=sat-25544). It flies a little over 400 kilometres up, a four-hour drive if the road went straight up, at about 28,000 kilometres an hour, and laps the planet roughly every hour and a half. You see it only near dusk and dawn, for a plain geometric reason: you have to be standing in the dark while the station, far above you, is still in sunlight. When it fades in mid-sky, it has just flown into the Earth’s shadow. For the people on board, that was a sunset. ![The International Space Station above the Earth with Space Radar’s live card showing its height and speed](/media/what-is-in-the-sky-tonight/04-06-iss.jpg) *The station’s height and speed, worked out live from its published orbit. NASA’s own description of a pass: like a very bright star moving across the sky, except that it does not blink or change direction.* A pass is the easiest wonder in astronomy. It needs no dark site, no equipment and no patience, only the time and the direction, which [NASA’s Spot the Station](https://www.nasa.gov/spot-the-station/) or any pass predictor will give you. The other satellites are harder. In the hour after sunset you may notice faint, steady points sliding between the stars. There are thousands of them now, and almost all are too dim for a city sky. ## The sky your great-grandmother could read For most of history, knowing the sky was not a hobby. It was the clock, the calendar and the compass. Around 700 BC the Greek farmer-poet Hesiod told his brother when to work: begin the harvest when the Pleiades rise, and the ploughing when they set. Jewish law still defines the end of the day by observation. The Talmud says that night has come when three medium-sized stars can be seen, a rule that takes for granted that anybody can step outside and judge the stars for themselves. And for sailors in the northern hemisphere the height of the Pole Star above the horizon simply *was* their latitude. ![The winter evening sky over Tel Aviv looking south-east: Orion with Betelgeuse and Rigel, Sirius below it, Procyon, Gemini, and bright Jupiter low in the east](/media/what-is-in-the-sky-tonight/04-10-winter-sky.jpg) *The same balcony three months later, on 10 January 2027 at 21:00. Orion’s three belt stars point down to Sirius, the brightest star in the sky. The brighter light in the east is not a star: Jupiter.* The method they all used is still the best one. Nobody memorises the sky. You learn one figure and step from it to the next, the way you learn a new city from a single street. Orion’s belt points one way to Sirius and the other way towards Aldebaran and the Pleiades. The two end stars of the Plough point to the Pole Star. The 88 constellations on a modern chart were agreed by astronomers only in 1922, but the paths between them are thousands of years old. If you want a guide for the first walk, [take the tour of the constellations](https://www.spaceradar.ai/#trip=the-constellations). **Fly there in the 3D map:** [Take the tour of the constellations](https://www.spaceradar.ai/#trip=the-constellations) ## The one pollution that leaves at the speed of light There is one thing to be said for light pollution. It has no residue. Carbon stays in the air for centuries and plastic stays in the sea. Shade a lamp or switch it off, and its share of the glow is gone before your hand leaves the switch. > Shade a lamp or switch it off, and its share of the glow is gone before your hand leaves the switch. That is why the dark is coming back in places. [DarkSky International](https://darksky.org/what-we-do/international-dark-sky-places/) has certified more than 200 Dark Sky Places in 22 countries as of 2026: parks, reserves and whole towns that have agreed to aim their lamps at the ground, keep them warm in colour and no brighter than they need to be. The Ramon Crater in Israel’s Negev desert became the first in the Middle East in 2017. None of these places is unlit. They light the pavement and leave the sky alone. ## Ten minutes tonight Go outside about an hour after sunset. Stand with the nearest lamp behind you, and put the phone in your pocket: the eye needs twenty to thirty minutes to reach full night vision, and a single bright screen sends it back to the start. Ten minutes is enough to begin. Look for the brightest light that does not twinkle. That is a planet. Then find one figure, any one, and one star in it whose name you will remember tomorrow. If the station is due, wait for it. All of this is laid out for your own place in [tonight’s sky from your street](https://www.spaceradar.ai/#trip=tonight-from-your-street), and when you want the open sky itself, [the Tonight view](https://www.spaceradar.ai/#m=now) shows it for any hour you choose. It guesses your place from your time zone, so tell it your town first. Then, on some clear weekend near new Moon, drive to a gap between the lights. The sky that puzzled Los Angeles in 1994 is still there every night, behind the glow, waiting for a power cut or for forty minutes in a car. > **About Space Radar.** Space Radar is a free, open-source live 3D map of everything in orbit and of the sky from where you stand. It runs in a browser at [spaceradar.ai](https://www.spaceradar.ai/), with no account. **Fly there in the 3D map:** [The planets tonight, from your street](https://www.spaceradar.ai/#trip=planets-tonight). Free, in your browser, no account. ## Questions people ask ### What planets are visible tonight? Up to five can be seen without a telescope: Mercury, Venus, Mars, Jupiter and Saturn. Which of them are up depends on the date and on where you are; in mid-October 2026, from mid-northern latitudes, Saturn is up all evening and Jupiter and Mars before dawn. ### How do I tell a planet from a star? A planet shines with a steady light, while stars twinkle, most of all near the horizon. Planets also keep close to the path the Sun and Moon follow across the sky. ### Can I see the International Space Station without a telescope? Yes. It looks like a very bright star that moves steadily across the sky for a few minutes, without flashing lights, and it is visible only within a few hours of sunset or sunrise. ### Why can I not see the Milky Way from my city? It is still there, but the glow of artificial light scattered in the air outshines it. More than a third of humanity lives where it cannot be seen at all. ## Sources 1. [A world atlas of artificial night-sky brightness](https://www.science.org/doi/10.1126/sciadv.1600377) 2. [Analysed 51,351 observations](https://noirlab.edu/public/news/noirlab2302/) 3. [A dozen or two](https://coolcosmos.ipac.caltech.edu/ask/206-How-many-stars-can-you-see-at-night-) 4. [NASA’s Spot the Station](https://www.nasa.gov/spot-the-station/) 5. [DarkSky International](https://darksky.org/what-we-do/international-dark-sky-places/) 6. [Dus32w6mqcntr.cloudfront.net](https://dus32w6mqcntr.cloudfront.net) 7. [Earthquake.usgs.gov: executive](https://earthquake.usgs.gov/earthquakes/eventpage/ci3144585/executive) 8. [Nps.gov: connect](https://www.nps.gov/subjects/nightskies/connect.htm) 9. [Discovermagazine.com: for our own good let there be dark 40401](https://www.discovermagazine.com/for-our-own-good-let-there-be-dark-40401) 10. [Arxiv.org: 1609.01041](https://arxiv.org/abs/1609.01041) 11. [Science.org: science.abq7781](https://www.science.org/doi/10.1126/science.abq7781) 12. [Gfz.de: citizen scientists report global rapid reductions in the visibility of stars from 2011 to 2022](https://www.gfz.de/en/press/news/details/citizen-scientists-report-global-rapid-reductions-in-the-visibility-of-stars-from-2011-to-2022) 13. [Earthsky.org: how many stars could you see on a clear moonless night](https://earthsky.org/astronomy-essentials/how-many-stars-could-you-see-on-a-clear-moonless-night/) 14. [Cts.perseids.org](https://cts.perseids.org/read/greekLit/tlg0020/tlg002/perseus-eng2/375-385) 15. [Sefaria.org: Shabbat.35b](https://www.sefaria.org/Shabbat.35b) 16. [Jtsa.edu: babylonian talmud shabbat 35b](https://www.jtsa.edu/torah/babylonian-talmud-shabbat-35b/) 17. [Ru.wikipedia.org: Сочельник](https://ru.wikipedia.org/wiki/Сочельник) 18. [En.wikipedia.org: Pole star](https://en.wikipedia.org/wiki/Pole_star) 19. [Iau.org: constellations](https://www.iau.org/public/themes/constellations/) 20. [En.wikipedia.org: DarkSky International](https://en.wikipedia.org/wiki/DarkSky_International) 21. [Darksky.org: ramon crater named first international dark sky place in the mideast](https://darksky.org/ramon-crater-named-first-international-dark-sky-place-in-the-mideast/) 22. [Nps.gov: dark adaptation of the human eye and the value of red flashlights](https://www.nps.gov/articles/dark-adaptation-of-the-human-eye-and-the-value-of-red-flashlights.htm) 23. [Spaceradar.ai](https://www.spaceradar.ai) --- # ISS pass tonight? Ask the sky over your own street > Most sky apps assume you know the constellations. The Tonight view in Space Radar assumes you know which way is south. What it works out for one street on one evening, and what it admits it cannot know. By Ivan Akselrot. Published 2026-10-19. Category: Skywatching. Tags: ISS pass, tonight, visible passes, stargazing, ISS. 8 min read. Canonical: https://blog.spaceradar.ai/iss-pass-tonight-sky-from-your-street/ Friday 9 October 2026, half past seven in the evening, London. The Sun went down about an hour ago and the sky in the west is still the colour of weak tea. Say someone has stepped out onto the pavement with a phone, because a child asked whether you can see the space station from here. The question they type is the obvious one: is there an ISS pass tonight? I had asked exactly that, for London, two nights earlier, and the answer was not the one I hoped for. The station’s next pass was on Thursday morning at 09:19, two fists above the southern horizon, for about five minutes. Under the time there was one more sentence: “You would not see this pass: your sky is too light, or the station is in the Earth’s shadow.” That is a disappointing thing for a space map to say, and I think it is the most useful sentence on the page. This piece is about the part of Space Radar called Tonight: what it works out for one street on one evening, how it decides what is worth your ten minutes outside, and what it admits it cannot know. ![An ISS pass tonight view for London: a dusk sky with constellation lines over a city skyline, and a panel listing Jupiter, Tiangong, Saturn, the Pleiades and the Andromeda Galaxy with times and heights](/media/iss-pass-tonight-sky-from-your-street/09-01-tonight-london.jpg) *London at 19:30 on 9 October 2026, looking south-east. The panel’s last lines read “Dark 19:30 to 06:42 · no Moon, a dark night” and “Computed for your place. Brightness is an estimate.”* ## A list of seven, not a timetable Look at what the panel offers instead. Saturn, at magnitude 0.2, best at half past midnight, forty degrees up in the south. Jupiter before dawn, brighter still. The Pleiades by eye at 03:30. The Andromeda Galaxy, with the word “binoculars” beside it. China’s station, Tiangong, at 05:57, but only eleven degrees up. That is the whole list, and its shortness is a rule. The code that ranks it says so in a comment I like: a row’s score is how easy the thing is to see, “a rule, not a taste”. Brightness counts most, then height. At most seven rows, and never more than three satellite passes, because “this is a list of what to look at, not a timetable”. Two of the satellites in the list have a dash where their brightness should be. The map holds a published standard brightness for exactly two objects, the two space stations. For everything else it does not know, and so it prints “—”. A dash is less impressive than a number, and it is true. Heights are given in degrees and, in the trips, in fists. A fist held at arm’s length covers [about ten degrees](https://earthsky.org/astronomy-essentials/sky-measurements-degrees-arc-minutes-arc-seconds/) of sky, which is the only instrument most of us carry. ## What “visible” means Back to the pass at 09:19. The station was there. It crossed the sky above London exactly as computed, 429 kilometres up. Nobody could have seen it, for the same reason nobody sees the stars at breakfast. A satellite has no light of its own that you could see from the ground. You see sunlight bouncing off it. So three things have to be true at once, and the map checks all three: the satellite is high enough, more than ten degrees above your horizon; it is in sunlight; and you are in the dark, with the Sun at least six degrees below your own horizon. NASA’s own guidance says the same thing in plainer words: all sightings fall [within a few hours before or after sunrise or sunset](https://www.nasa.gov/spot-the-station/). In the middle of the night it fails the other way. You are in the dark, and so is the station, which has followed you into the Earth’s shadow. The small arc the map draws for each pass shows this: a solid line while the object is sunlit, a dashed one once it has gone into shadow. Many evening passes simply stop half way up the sky. ![The International Space Station above a blurred view of land and sea, with a card titled The next time it crosses your sky that ends You would not see this pass](/media/iss-pass-tonight-sky-from-your-street/09-05-pass.jpg) *The station at the top of its next pass over London, 1,116 kilometres from the observer. The card’s own caveat: the model is drawn 260 pixels wide whatever the distance; “the real station would be a bright dot”.* You can ask this of any satellite. Open [the space station’s card](https://www.spaceradar.ai/#at=sat-25544) and “When you can see it” gives the next pass for your place, or [the last stop of the trip up to the station](https://www.spaceradar.ai/#trip=journey-to-the-station&stop=4) flies you to it. The same goes for [Tiangong](https://www.spaceradar.ai/#at=sat-48274), the other place where people live up there. **Fly there in the 3D map:** [The space station’s card](https://www.spaceradar.ai/#at=sat-25544) > You would not see this pass: your sky is too light, or the station is in the Earth’s shadow. ## It does not assume you know the constellations Most astronomy apps are built around a star chart, and a star chart is a wonderful thing if you can already read one. Tonight starts from the other end. It gives a name you know, a clock time, a height and a compass direction: “best 00:30 · 40° up, S”. If you can find south, you can find Saturn. There are buttons for the sky you really have. North, East, South, West, for a window that faces one way. “Above 15°” and “Above 30°”, for a street with buildings on it. Dusk, Midnight and Dawn, to move the whole sky to the hour you will be awake. When you do want the figures, they are there, and not only ours. The lines can be switched to pictures, drawn by the artist Johan Meuris for [Stellarium](https://stellarium.org/) and shared under a free licence. And the 88 constellations that [astronomers agreed on in 1922](https://www.iau.org/public/themes/constellations/) can be exchanged for the Chinese sky, the Māori or the Hawaiian. Over London that Friday the patch of sky we call Aquarius holds, in the Chinese reading, the Rooftop, the Tomb, the Weeping and the Crying, and a pair of Deified Judges. ![The same London dusk sky labelled with the Chinese constellations, in Chinese characters and English: Rooftop, Encampment, Weeping, Crying, Deified Judge of Right and Wrong](/media/iss-pass-tonight-sky-from-your-street/09-07-chinese-sky.jpg) *The same stars, another people’s map. The sky-culture data comes from the Stellarium project’s contributors; one culture was left out because its licence forbids commercial use.* ## Your street, honestly The harder question is whose sky this is. The answer is: roughly yours, and the page tells you how roughly. It needs a place. With none set, it guesses from your device’s time zone and says that it is a guess. It does not look up your address from the network. You can pick a city from a list or let the browser share your position, behind a tap. The place stays in your browser. It needs to know how dark your sky is, and it does not ask. It reads NASA’s map of the Earth’s lights at night for your spot and decides: city, town or dark place. For central London the line is blunt: “City: stars to magnitude 4, no Milky Way.” You can overrule it, and see what the same evening would look like from a field. And it needs a horizon, which it cannot have. So it draws one, hills or roofs, and labels it. Under all the switches is a single sentence that sorts the whole picture into what kind of truth each part is: - **4 words** for the four kinds of truth in the sky view: “Stars measured, planets computed, air modelled, land drawn.” There is also a red switch. Red is the traditional colour of an observer’s torch, the one that is kindest to eyes that have got used to the dark, and one tap turns the whole page that colour. ![The Tonight view in red night mode, with illustrated constellation figures over the skyline and all the panel text in red](/media/iss-pass-tonight-sky-from-your-street/09-06-red-night.jpg) *Red light, with the constellation pictures switched on. The row of four buttons in the panel chooses whose constellations are drawn: Western, Chinese, Māori or Hawaiian.* ## On the pavement Everything above is on the phone as well, which is where it belongs. The sheet at the bottom slides out of the way and the sky fills the screen; the time bar stays, so a thumb can pull the evening forward to the hour the station comes. ![A phone screen showing the dusk sky over a skyline with the constellation Aquarius marked, a time bar and the tabs Earth, Planets, Stars and Tonight](/media/iss-pass-tonight-sky-from-your-street/09-11-phone.jpg) *The same evening on a phone. The bar above the tabs is time: drag it and the sky moves to that hour.* It has limits that no panel can fix. It does not know about your clouds; one of its own sentences ends “weather allowing”. A pass is only as good as the orbital data it was worked out from, which the card dates. The brightness of anything but the two stations is an estimate or a dash. All of it is in English. But the list is short, and it is for your street. There is a seven-stop trip that walks through it in order, [tonight from your street](https://www.spaceradar.ai/#trip=tonight-from-your-street): a first star, one figure, the Moon if it is up, a planet, the station’s next pass. Or open [the Tonight view](https://www.spaceradar.ai/#m=now) itself and tell it your town. **Fly there in the 3D map:** [Tonight from your street](https://www.spaceradar.ai/#trip=tonight-from-your-street) Then put the phone in your pocket. On an October evening in 2026, face south-east, and look for the one steady light that does not twinkle. That is Saturn, about 1.3 billion kilometres away, and it needs no pass at all. > **About Space Radar.** Space Radar is a free, open-source live 3D map of everything in orbit, and of the sky from where you stand. It runs in a browser at [spaceradar.ai](https://www.spaceradar.ai/), with no account; the code is on [GitHub](https://github.com/Sara-Managed-Projects/space-radar). **Fly there in the 3D map:** [Tonight, from your street](https://www.spaceradar.ai/#trip=tonight-from-your-street). Free, in your browser, no account. ## Questions people ask ### Is there an ISS pass tonight where I live? It depends on your place and the date; there are stretches of days with no visible pass at all. A tracker that knows your location lists the next ones, and should say whether each can actually be seen. ### Why can I only see the space station around dusk or dawn? Because you are seeing sunlight on it. The station must be in sunshine while you are in darkness, which happens in the hours after sunset and before sunrise. ### How do I find a planet without knowing the constellations? Use a time, a compass direction and a height. A planet is a bright point that does not twinkle; a fist at arm’s length is about ten degrees. ### Does Space Radar need my location? No. It guesses a place from your time zone and says so; you can choose a city by hand. Nothing about your place is sent to a server. ## Sources 1. [GitHub](https://github.com/Sara-Managed-Projects/space-radar) 2. [About ten degrees](https://earthsky.org/astronomy-essentials/sky-measurements-degrees-arc-minutes-arc-seconds/) 3. [Within a few hours before or after sunrise or sunset](https://www.nasa.gov/spot-the-station/) 4. [Astronomers agreed on in 1922](https://www.iau.org/public/themes/constellations/) 5. [Spaceradar.ai](https://www.spaceradar.ai) 6. [Astronomy.com: sky this month october 2026](https://www.astronomy.com/observing/sky-this-month-october-2026/) 7. [Heavens-above.com: faq.aspx](https://www.heavens-above.com/faq.aspx) --- # A live satellite map that tells you when it is guessing > Space Radar draws everything in orbit where it really is, for people who have never heard of an orbital element. Why I think a map of space has to be honest and kind at once, what that costs, and why it is free and open. By Ivan Akselrot. Published 2026-10-17. Category: How It's Built. Tags: open source, 3D map, honest data, accuracy, satellites. 11 min read. Canonical: https://blog.spaceradar.ai/live-satellite-map-open-source/ At twenty-five past midnight, Universal Time, on 8 October 2026, the Hubble Space Telescope was 468 kilometres above the night side of the Earth, moving at 27,485 kilometres an hour, and seventeen minutes away from its next sunrise. I know this because a live satellite map in my browser told me. Under those numbers, in small grey type, the same page added a sentence that most pages about space would rather not print: “Position propagated from elements 33 hours old.” That line is a confession. Nobody was looking at Hubble at that minute. A radar had measured its orbit a day and a half earlier, and my laptop had done the arithmetic to carry it forward. The dot on the screen was a very good estimate, and the page said that it was one. I build that page. It is called Space Radar, and it draws everything in orbit, and beyond it the Moon, the planets, the stars and the galaxy, each where it is at this second. The small grey line is the most important thing in it. This piece is about why: what it takes to show space as it really is to a person who became curious five minutes ago, and why I think the result has to be free, open, and willing to say “we do not know”. ![A live satellite map in a browser: the Earth half in daylight and half in night with city lights, satellites as small marks around it, and a panel listing what is happening in space today](/media/live-satellite-map-open-source/07-01-home.jpg) *The first screen, as it was on 8 October 2026: four named storms, the people in orbit, an asteroid passing in nine hours. The line at the foot of the panel reads “15 sources read · 4 stale · oldest a day ago”.* ## Two kinds of space website, and the gap between them There have been good satellite trackers on the web for decades, and nearly all of them were built by people who already know what an element set is. It is a short row of numbers that describes one orbit: how big, how tilted, how stretched, and where on it the object was at a stated moment. The numbers come from radar and telescope tracking, and since 1985 a great many of them have reached the public through [CelesTrak](https://celestrak.org/), the service run by the astrodynamicist T. S. Kelso. A tracker turns those rows into dots. The good ones are exact and generous, and they greet you with the words apogee, inclination and NORAD ID. At the other end are the beautiful ones: films and apps in which space looks the way we feel it should. They are patient with a beginner. They are also, often, closed, and what they show is a picture of space more than a reading of it. You cannot ask the picture how it knows. Between them there are things I admire. [Stellarium](https://stellarium.org/) has been an honest, open-source sky from the ground since 2001. NASA’s Eyes is a superb way to ride along with NASA’s own missions. What I could not find was one place that had the tracker’s truth and the film’s patience, for all of it at once: the satellite over your head, the rover on Mars, the star behind both. The project’s README states the aim in three short claims. Learning about space should be free and simple. It should run anywhere. It should be honest. Everything else is a consequence. ## What a live satellite map costs to get right Start with the arithmetic. Each satellite is moved by a model called SGP4, which goes back to the punch-card days of American space tracking and is still the one the public element sets are written for. It runs in your browser, for thousands of objects, again and again. Asteroids and comets go by Kepler’s equation. The Sun, the Moon and the planets come from an ephemeris library, which is why they are right for a date centuries away and a satellite is not. Then the manners. CelesTrak refreshes its files every two hours and asks every program to download each file once per update; ignore that, its [usage policy](https://celestrak.org/usage-policy.php) says, and your address goes to the firewall. So the map keeps a cache, never asks twice, and treats a refusal as an answer and not as a reason to retry. You can [follow Hubble live](https://www.spaceradar.ai/#at=sat-20580) and read at the foot of its card how old the copy is. **Fly there in the 3D map:** [Follow Hubble live](https://www.spaceradar.ai/#at=sat-20580) ![The Hubble Space Telescope above the night side of the Earth, with a card giving 468 km up, 27 485 km/h and 94 minutes a lap, and the line Position propagated from elements 33 hours old](/media/live-satellite-map-open-source/07-02-hubble-card.jpg) *Hubble in the Earth’s shadow, seventeen minutes before sunrise. The bar under the numbers is one lap: pale where the telescope is in sunlight, dark where it is not.* The hard part is not the mathematics. It is deciding what you are allowed to draw. The project keeps three words for this, and every card carries one of them in a line at its foot. *Measured*: a position worked out from a publisher’s data of a stated age. *Modelled*: computed from physics, with the error measured where it could be. *Illustrative*: a picture built to explain. The aurora on the night side is where NOAA’s forecast expects it in the next hour, and the card says “not a photograph”. The spiral of [the Milky Way seen from outside](https://www.spaceradar.ai/#trip=to-the-edge&stop=6) is an illustration, because nobody has ever been outside it with a camera. My favourite example is a small moon of Uranus. [Miranda](https://www.spaceradar.ai/#at=miranda) is about 472 kilometres across and 2.6 light-hours away. Drawn to scale from here it would be nothing at all, so the map cheats, and then it tells you exactly how. Its card says: “Uranus is drawn 388 times wider on the sky than it looks, so you can find it”, and Miranda “is drawn bigger still, or it would be too small to see.” ![Miranda, a moon of Uranus, drawn as a plain grey ball, with a card that explains how much larger than life it and Uranus are drawn](/media/live-satellite-map-open-source/07-10-miranda.jpg) *Miranda on 8 October 2026, drawn as a plain grey ball: 18.8 times the Earth–Sun distance away, a radio signal 2.6 hours each way. The grey paragraph in the card is the admission.* > Missing is shown as missing. Never a guess dressed as a reading, never an empty layer presented as an empty sky. That is from the project’s one-page design rules, and it has a practical edge. When a source cannot be read, the map does not show a sky with nothing in it. It says “could not look”. That is a third answer, different from “nothing there” and different from “all fine”, and a beginner deserves to be told which one they are getting. ## The person who just got curious Honesty alone would give you a very correct table. The other half of the idea is kindness, and it is mostly made of small refusals. A label says “Height”, not “apogee”. A card leads with three large numbers and puts the explanation one tap further in. No line of interface is longer than sixty characters. People type “station” into a search box and mean the International Space Station; the catalogue calls it ISS (ZARYA); a small file of aliases exists so that the person is right and the catalogue adjusts. For someone who does not know what to ask, there are guided trips: 26 of them as I write, 205 stops, a little over an hour of narration. The camera flies, a voice reads one short card at each stop, and the cards are written, by rule, for a curious twelve-year-old. One trip stands you at [the place where the first people landed on the Moon](https://www.spaceradar.ai/#trip=moon-landings&stop=2). Another pauses at [Saturn, backlit, with its rings](https://www.spaceradar.ai/#trip=outer-solar-system&stop=3). **Fly there in the 3D map:** [The place where the first people landed on the Moon](https://www.spaceradar.ai/#trip=moon-landings&stop=2) ![The Apollo 11 lunar module standing on the grey surface of the Moon, with a card titled The first people](/media/live-satellite-map-open-source/07-06-apollo-11.jpg) *Stop two of ten on the Moon-landings trip. Armstrong and Aldrin’s whole walk covered about 250 metres; the card’s last line says the lander’s position is measured.* And there is the teacher in a village where the signal comes and goes. For her the project keeps a budget, enforced by a test: a first visit may download no more than 4.0 megabytes, and the stated reason is “it has to open on a school connection”. The whole thing is a folder of files that runs from a laptop with no internet at all, and when it does, it says how many days old its saved data is. ![Two phone screens side by side: the Earth with satellites and a time bar, and the International Space Station with its height, speed and minutes per lap](/media/live-satellite-map-open-source/07-11-phone-pair.jpg) *The same map on a phone: one sheet, one thumb. On the right the station is 424 kilometres up, and the grey line gives the age of its elements as 36 hours.* - **4.0 MB** is the most a first visit is allowed to download. The reason written beside the number: “It has to open on a school connection.” ## Why it costs nothing and asks for nothing There is no account because there is nothing to log in to. Space Radar is a static website: the page and the public data arrive, and the physics runs on your own device. No database knows you were there. No advert pays for the visit, and no tracker follows you out. That is also what makes free sustainable. There is no server-side code to keep alive, only files. A school can put the folder on its own computer and never speak to us again. The code is under the [MIT licence](https://opensource.org/license/mit), which in plain words means: copy it, change it, build on it, keep the notice. The data is not ours to license. It belongs to the people who publish it for free, and the file that lists them, with each licence and each required credit line, runs to some 1,800 lines. It ends its summary with a sentence I would like more projects to print: none of these organisations endorses Space Radar. ## Built in the open, with the machines in the room The [repository on GitHub](https://github.com/Sara-Managed-Projects/space-radar) was opened on 7 September 2026. In its first month it took in about three hundred merged changes, and the README says plainly how: much of the project was written by people working with AI assistants, “held to account by tests and by sources”. The second half of that sentence is the one that matters. A fact on a card needs a source and the date it was read, and the automated checks refuse a row without them. Adding a moon, a landing site or a whole trip is a row in a [registry of plain text files](https://github.com/Sara-Managed-Projects/space-radar/tree/main/registry), not a change to the program, and one of the tests adds a moon of Saturn using rows alone and fails if that ever needs code. So what the project asks of people is modest. You do not need to be a graphics engineer. The ten-minute first contribution in the [contributor guide](https://github.com/Sara-Managed-Projects/space-radar/blob/main/CONTRIBUTING.md) is teaching the search box one word. A report that a number is wrong, with a link to who says so, is described there as gold. So are notes from anyone who has tried it in front of a real class. It has limits, and here they are. The interface is in English only; every word a visitor reads lives in one file, which is where a translation would start, and nobody has started one. The voice that reads the trips is synthetic and says so. Today’s clouds are real only where the weather satellites it reads can see; over Europe, Africa and the Indian Ocean they are a stand-in, and labelled as one. A satellite’s place more than a week from now is marked “rougher” on the timeline. The README still says 25 trips. And one open issue describes the Moon, up close, as “a soft painted ball”. Where it goes next is written in the same public list. Hold the phone up and have the sky on the screen match the sky overhead. A badge that says “drawn N times larger”, with a switch to true scale. None of it is promised. All of it is where anyone can argue with it. ![The Milky Way seen from outside as a spiral of white points, an illustration built from published measurements](/media/live-satellite-map-open-source/07-08-milky-way.jpg) *The one view on the map that nobody could photograph: our galaxy from outside, at a stop of the trip “To the edge of what we know”. It is an illustration built from measurements, and its card says so.* ## The grey line If you take one thing from this, take the habit. [Open the map](https://www.spaceradar.ai/), tap whatever is passing over your part of the world, and read the last line on its card before you read anything else. Ask the same of every chart of the sky you are ever shown: how old is this, who measured it, and what did you make up? Then, if a number of ours is wrong, tell us, and bring your source. > **About Space Radar.** Space Radar is a free, open-source live 3D map of everything in orbit: satellites, stations, debris, rockets, planets and stars, each at its real, computed position. It runs in a browser at [spaceradar.ai](https://www.spaceradar.ai/), with no account. **Fly there in the 3D map:** [To the edge of what we know](https://www.spaceradar.ai/#trip=to-the-edge). Free, in your browser, no account. ## Questions people ask ### Is there a free live satellite map that needs no account? Yes. Space Radar runs in a browser, shows satellites at positions computed from public orbital data, and has no sign-up, adverts or tracking. Other free trackers exist too; most assume you know the vocabulary. ### How does a satellite map know where the satellites are? It does not watch them. It downloads published orbital elements, measured by radar and telescopes a few hours or days earlier, and computes each position forward with a standard model called SGP4. ### Is Space Radar open source? Yes. The code is on GitHub under the MIT licence. The maps, catalogues, photographs and models it draws keep their own publishers’ licences, which are listed in the repository. ### Can it be used in a classroom without the internet? Yes. It is a folder of files that any computer can serve to a browser, with a saved copy of the changing data, and it states how old that copy is. ## Sources 1. [Repository on GitHub](https://github.com/Sara-Managed-Projects/space-radar) 2. [Usage policy](https://celestrak.org/usage-policy.php) 3. [Stellarium](https://stellarium.org/) 4. [MIT licence](https://opensource.org/license/mit) 5. [Spaceradar.ai](https://www.spaceradar.ai) 6. [Space-track.org: documentation](https://www.space-track.org/documentation) 7. [Celestrak.org: brief history](https://celestrak.org/brief-history.php) 8. [Science.nasa.gov: eyes](https://science.nasa.gov/eyes/) --- # How accurate is satellite tracking? Follow the numbers > A map of space is a pile of other people’s measurements. Who made them, how old they are, which parts are computed, which are photographs and which are honest drawings, and how to send a correction when one of them is wrong. By Ivan Akselrot. Published 2026-10-15. Category: How It's Built. Tags: accuracy, TLE, SGP4, data sources, satellites. 10 min read. Canonical: https://blog.spaceradar.ai/how-accurate-is-satellite-tracking/ There is a sentence on my screen this morning that nobody wrote. It says: “The oldest thing still in orbit is Vanguard 1, launched in 1958: 68 years of laps.” It is true. Vanguard 1 went up on 17 March 1958, and NASA still describes it as [the oldest artificial object orbiting the Earth](https://www.nasa.gov/image-article/vanguard-satellite-1958/). But the sentence on the screen did not come from NASA. A small piece of code read a catalogue of everything in orbit, found the earliest launch date among the things that have not come down, and made a sentence out of it. That is a nice trick, and it should make a careful reader slightly uneasy. Who keeps the catalogue? How old is this copy of it? What else on the page is generated, computed, photographed or simply drawn? People ask how accurate satellite tracking is as if there were one answer. There are several, and this piece follows the numbers on Space Radar back to where each of them comes from. ![How accurate is satellite tracking: the Earth surrounded by thousands of blue marks, one for each working satellite, with a panel of layer switches and counts](/media/how-accurate-is-satellite-tracking/12-09-everything.jpg) *Every working satellite the map could place on 8 October 2026: 16,626 of them. Each mark is drawn far larger than the satellite; from this distance the real things would be invisible.* ## Somebody else’s radar Space Radar has no radar. Neither does any other satellite map you have used. The watching is done by the United States Space Force, whose 18th Space Defense Squadron keeps the catalogue of tracked objects and produces, for each one, a short set of numbers describing its orbit. The military’s own site, Space-Track, [defines such a set](https://www.space-track.org/documentation) as “a mathematical representation of a satellite’s mean orbit”. Those sets are republished for everyone by [CelesTrak](https://celestrak.org/), and that is where the map reads them. It reads them politely, at most once per update, through a copy that the project saves so that thousands of visitors do not become thousands of requests. You can see the chain on any object. Open [the space station’s card](https://www.spaceradar.ai/#at=sat-25544) and tap “Sources for this record”. This morning it said, in order: that the shape on screen is drawn from a published model; that the orbit comes from CelesTrak’s list of crewed stations; and that the position was “propagated from elements 36 hours old”. **Fly there in the 3D map:** [The space station’s card](https://www.spaceradar.ai/#at=sat-25544) ![The International Space Station above the Earth with its card open at Sources for this record, naming CelesTrak and giving the age of the elements](/media/how-accurate-is-satellite-tracking/12-07-iss-sources.jpg) *The station’s card with its sources open. Three different kinds of claim are kept apart: where the shape comes from, where the orbit comes from, and how old the orbit is.* ## Even “measured” is generous So how accurate is the dot? The honest answer has two parts. Near the moment the numbers were made, quite good. For a typical low orbit the standard model is reckoned to be right to about a kilometre within a few days. For something moving at nearly eight kilometres a second, a kilometre is an eighth of a second. After that it decays, and not gently. A low satellite ploughs through thin air that nobody can forecast well, and the error grows by something like a kilometre a day, faster for small light things. This is why Space-Track itself warns that its public numbers are not good enough for deciding whether two objects will collide. The map’s own code is blunt about the vocabulary. A position is labelled “measured” only within twelve hours of the day its numbers were made, and “worked forward from an older measurement” after that. Above the line that sets the twelve hours, a programmer has left this: > A TLE is a fit, not an observation, so even “measured” is generous. A TLE is the old two-line format of those orbit numbers. The comment is right. No radar saw the station where the dot is. Radars saw it in several places some hours ago, a curve was fitted through them, and your browser has extended the curve. ## Two counts that disagree, and are both right Now the big number. How many things are up there? On the home screen there is a quiet link, “Debris, by the numbers”. Tap it and the map reads CelesTrak’s whole catalogue and counts. On 8 October 2026 its answer was: “17 450 of the 34 570 things tracked in orbit no longer work.” Of the rest, 17,066 were working satellites, and one stop of a trip shows [all of them at once](https://www.spaceradar.ai/#trip=satellites-and-junk&stop=2). **Fly there in the 3D map:** [All of them at once](https://www.spaceradar.ai/#trip=satellites-and-junk&stop=2) The European Space Agency, whose debris office [publishes its own figures](https://sdup.esoc.esa.int/discosweb/statistics/), gives a different total: about 47,140 objects regularly tracked, and about 15,900 satellites still functioning, as of its update of 31 July 2026. Neither is wrong. They are counting on different days, from different lists, with different rules for what counts as catalogued and what counts as working. A map that printed one of them without a date would be hiding that. The panel prints where its count came from and when: “Counted from CelesTrak’s catalogue as read on 6 October 2026: what radar can track, from about 10 cm across.” ![The Earth wrapped in thousands of grey and yellow dots, with a panel giving 34 570 things tracked, 12 347 pieces of debris, and counts by height](/media/how-accurate-is-satellite-tracking/12-02-debris.jpg) *The debris view. The counts are the catalogue’s. The places are not, and the panel says so: each dot is “at its real height and tilt, at a made-up place on its orbit”.* That caption deserves a second look. The catalogue the count is made from gives each object’s orbit but not where on the orbit it is this minute. So the dots are in the right shell, at the right tilt, at an invented point along the way. A prettier map would not have mentioned it. Smaller pieces are not in any catalogue. The panel quotes ESA’s model for those, about 1.5 million pieces between one and ten centimetres, and adds four words: “An estimate, not a count.” - **34,570** things tracked in orbit, by the count the map made from CelesTrak’s catalogue on 6 October 2026. ESA, counting differently, says about 47,140. ## Computed, catalogued, photographed Satellites are the shakiest numbers on the map. Almost everything else is firmer, and it helps to sort it into three piles. **Computed.** The Sun, the Moon, the planets and their moons are worked out afresh for the instant on the clock, from physics that holds for centuries. Nothing is downloaded. An eclipse in 2028 is as trustworthy as the Moon tonight. **Catalogued.** The stars are a list somebody measured. The 109,389 stars the map draws in three dimensions come from a public compilation built on the European satellite Hipparcos, and the build script says exactly what it kept: 119,614 rows in, and 10,224 of them “counted and not drawn” because nobody has measured their distance. Fainter stars might have come from Europe’s newer Gaia catalogue. They do not, and the credits file explains why: Gaia’s archive forbids commercial reuse, the project ships nothing under such a licence, “so nothing was downloaded”. **Photographed.** Thirty nebulae and galaxies on the map are real photographs, placed where the objects are in the sky, from the European Southern Observatory, the Hubble and Webb telescopes and America’s NOIRLab. Each carries a line under it. For [the Orion Nebula](https://www.spaceradar.ai/#trip=through-a-telescope&stop=2) it reads: “A real photograph, placed where it is in the sky. Picture: ESO/G. Beccari · CC BY 4.0, edges faded and sky darkened by us.” **Fly there in the 3D map:** [The Orion Nebula](https://www.spaceradar.ai/#trip=through-a-telescope&stop=2) ![The Orion Nebula as a colour photograph against black space, with a card titled With a camera and a credit line naming ESO and G. Beccari](/media/how-accurate-is-satellite-tracking/12-03-orion-credit.jpg) *The Orion Nebula, 1,344 light-years away. The card says whose photograph it is, under [what licence](https://www.eso.org/public/outreach/copyright/), what was changed, and why the red is stronger than an eye would find it.* And then there are things that look like photographs and are not. The map takes care over those. The colours on [the sea in the living-Earth trip](https://www.spaceradar.ai/#trip=the-living-earth&stop=5) are temperatures: “Measured, with the gaps filled in… A map of data, not a photograph.” The glowing ring of [the first black hole ever pictured](https://www.spaceradar.ai/#trip=black-holes&stop=5) is the Event Horizon Telescope’s own image, made with radio waves, and its card adds: “It is drawn far larger than it would look from here; the place is measured.” ![The Atlantic and the Americas coloured from purple at the poles to red at the equator, with a key from 0 to 32 degrees and a card titled The sea moves the heat](/media/how-accurate-is-satellite-tracking/12-04-sea-temperature.jpg) *Sea surface temperature, from satellites and buoys. The small print gives the day the data is from, 6 October 2026, and its publisher, NASA’s Jet Propulsion Laboratory.* ![An orange ring around a dark centre, the Event Horizon Telescope's picture of the black hole in the galaxy M87, with a card titled The first picture of a black hole](/media/how-accurate-is-satellite-tracking/12-08-m87.jpg) *M87’s black hole, 53.5 million light-years away. The picture is real, made by eight radio observatories working as one; its size on the screen is not, and the card says so.* ## The page that says how it is doing All of this would be easy to promise and quietly let slip. So there is a panel that reports on the map itself. It opens from the line at the foot of the sidebar, and its first sentence is: “Every source it reads, how old that reading is, and where it comes from. Nothing here is hidden in a footer.” Each source has one of three states. *Ok*: read recently. *Stale*: a copy is held and it is older than it should be. And a third, which most software pretends does not exist: *could not look*. The code is firm that this is “a third answer”, not a kind of failure and certainly not a kind of success. ![The Sources panel listing CelesTrak, Launch Library, NOAA and other sources, each marked ok or stale, beside the Earth](/media/how-accurate-is-satellite-tracking/12-01-sources.jpg) *The Sources panel on 8 October 2026. It was not a flattering day: the project’s saved copies were a day old, and several rows read “stale · a fresher copy is overdue”.* I chose that screenshot on purpose. On the morning I took it the saved copies were a day old, and five sources, among them the one that counts the people living in orbit, were marked stale. The project’s public issue list has an entry about exactly this, the live site falling behind and its copies ageing. I would rather show you the panel on a bad day, because a status page that is only ever green is telling you nothing. ## Check it, then correct it Here is how to audit any number on the map in about a minute. Open the object. Read the last line of its card for the age. Open “Sources for this record” for the publisher. Then go to the publisher, which is always a public site, and look the object up there. If the two disagree, the project wants to hear. The [list of every source](https://github.com/Sara-Managed-Projects/space-radar/blob/main/registry/sources.yaml) the map reads is a text file, with the address of each and how often it may be asked. The [credits](https://github.com/Sara-Managed-Projects/space-radar/blob/main/CREDITS.md) list every licence. And there is a form for [reporting a wrong number](https://github.com/Sara-Managed-Projects/space-radar/issues/new?template=data-accuracy.yml) that asks four things: which object, what the map says, what is correct and who says so, and when you saw it. Its first line is the project’s whole attitude in a sentence: “Getting it right matters more to this project than anything else.” Start with Vanguard 1, if you like. A small satellite, launched in March 1958, still going round. [Find the debris view](https://www.spaceradar.ai/) and read the sentence about it. Then ask it the question you should ask every number about the sky: who says? > **About Space Radar.** Space Radar is a free, open-source live 3D map of everything in orbit and beyond, where every number says where it came from. It runs in a browser at [spaceradar.ai](https://www.spaceradar.ai/), with no account; the code and its sources are on [GitHub](https://github.com/Sara-Managed-Projects/space-radar). **Fly there in the 3D map:** [The ISS, with its numbers on the card](https://www.spaceradar.ai/#at=sat-25544). Free, in your browser, no account. ## Questions people ask ### How accurate is satellite tracking on public websites? For a low orbit, about a kilometre near the time the orbit numbers were made, getting worse by roughly a kilometre a day. It is good for finding a satellite in the sky and not good enough for predicting collisions. ### Where does satellite tracking data come from? Radars and telescopes run mainly by the United States Space Force track objects and publish their orbits. CelesTrak and Space-Track distribute them, and trackers compute positions from those numbers. ### How many satellites are in orbit? It depends on who counts and when. In October 2026 CelesTrak’s catalogue listed about 17,000 working satellites among 34,570 tracked objects; ESA’s figures from July 2026 give about 15,900 working. ### Are the pictures on Space Radar real photographs? Some are. Thirty nebulae and galaxies and two black holes are real images with their credit shown. Planets wear maps made from spacecraft pictures, and anything illustrative or false-colour is labelled. ## Sources 1. [GitHub](https://github.com/Sara-Managed-Projects/space-radar) 2. [The oldest artificial object orbiting the Earth](https://www.nasa.gov/image-article/vanguard-satellite-1958/) 3. [Defines such a set](https://www.space-track.org/documentation) 4. [CelesTrak](https://celestrak.org/) 5. [Publishes its own figures](https://sdup.esoc.esa.int/discosweb/statistics/) 6. [What licence](https://www.eso.org/public/outreach/copyright/) 7. [Spaceradar.ai](https://www.spaceradar.ai) 8. [Arxiv.org: 1002.2277](https://arxiv.org/abs/1002.2277) 9. [Nasa.gov: spot the station](https://www.nasa.gov/spot-the-station/) 10. [Astronexus.com: hyg](https://www.astronexus.com/projects/hyg) 11. [Cosmos.esa.int: hipparcos](https://www.cosmos.esa.int/web/hipparcos) --- # Where Is Voyager 1 Now? The Farthest Things We Threw > Where is Voyager 1 now? Almost exactly one day away at the speed of light, and still answering. A short tour of the farthest things people have thrown, and of the people who never stopped listening. By Ivan Akselrot. Published 2026-10-14. Category: Black Holes & Extremes. Tags: Voyager 1, deep space, JWST, New Horizons, interstellar. 10 min read. Canonical: https://blog.spaceradar.ai/where-is-voyager-1-now/ Suzanne Dodd has a way of explaining her job. If she says good morning to Voyager 1 at eight o’clock on a Monday, she told CNN last winter, she gets its answer at about eight o’clock on Wednesday. Dodd manages the Voyager project at NASA’s Jet Propulsion Laboratory in California. The machine she is talking to left Florida on 5 September 1977. It weighs less than a small car, and its computers run more than a million times slower than the phone in your pocket. And on Wednesday 18 November 2026, at 10:16 in the morning Universal Time, it will pass a mark nothing built by people has ever reached: 25.9 billion kilometres from the Earth, the distance a radio signal covers in exactly twenty-four hours. One light-day. So where is Voyager 1 now? In early October 2026 it is about 25.8 billion kilometres away, six minutes short of that line, and leaving at 17 kilometres every second. This piece is about what such a distance means, about the handful of other things we have thrown that far or left parked on the way, and about the people who have spent whole careers listening to one machine. I followed them on [Space Radar](https://www.spaceradar.ai/), a free live map that draws each of them where it has been computed to be today. ## A day away, at the speed of light Kilometres stop meaning anything long before Voyager. Time is the better ruler. Radio travels at the speed of light, so measure everything by how long a hello takes. The Moon is 1.3 seconds away. The Webb telescope is five seconds. The Sun is eight minutes and twenty seconds, which means that if it went out you would have time to make a coffee before you knew. New Horizons, the probe that flew past Pluto, is nine hours out. Voyager 2 is about twenty. And Voyager 1, in a few weeks, will be a full day: you can [see where Voyager 1 is right now](https://www.spaceradar.ai/#at=deep-voyager-1), with its distance, its speed and the number of days it has been travelling. **Fly there in the 3D map:** [See where Voyager 1 is right now](https://www.spaceradar.ai/#at=deep-voyager-1) - **23 h 54 min** The time a radio signal takes to reach Voyager 1 in early October 2026. On 18 November it becomes 24 hours. It took 49 years to get one light-day from home. The nearest star is 4.2 light-*years* away. At Voyager’s pace that distance would take about 75,000 years, and Voyager is not even pointed that way. The farthest thing we ever threw has, on the scale of the galaxy, barely left the porch. > The farthest thing we ever threw has, on the scale of the galaxy, barely left the porch. ![Space Radar’s card for Voyager 1 beside the spacecraft, showing its distance, speed and days since launch](/media/where-is-voyager-1-now/06-02-voyager-1-card.jpg) *The map’s reading on 7 October 2026: 172 AU from the Earth (one AU is the distance from the Earth to the Sun), 60,905 km/h, and 17,929 days in space. The position comes from the track NASA’s Jet Propulsion Laboratory publishes.* ## A fridge bulb, heard from interstellar space Here is the part that should not work. Voyager’s transmitter puts out about 23 watts, which NASA likes to compare to [the light bulb in a refrigerator](https://www.jpl.nasa.gov/images/pia17047-voyager-signal-spotted-by-earth-radio-telescopes/). By the time that signal has spread across 25 billion kilometres there is almost nothing left of it. NASA’s own comparison is that a digital watch runs on twenty billion times more power than a receiving dish collects from Voyager, and that figure dates from when the spacecraft was much closer. We hear it anyway, because the ears are enormous. NASA’s Deep Space Network has dishes 70 metres across in California, in Spain and in Australia, spaced round the planet so that one of them always faces the right way. Voyager 2 left the plane of the planets heading south, and can now be commanded from only one of them: the big dish near Canberra. When that dish was closed for repairs in 2020, Voyager 2 flew for eleven months with nobody able to tell it anything. The data comes home at 160 bits a second. One ordinary phone photo, sent at that speed, would take about two days. And the power is running out. Each Voyager carries a lump of plutonium whose heat is turned into electricity, and each year it makes about four watts less. The team has been switching off heaters and instruments one at a time to keep the transmitter alive: Voyager 1’s cosmic ray detector in February 2025, one of Voyager 2’s particle instruments a month later. ![Space Radar’s card for Voyager 2 with the spacecraft, showing its distance from the Sun and its speed](/media/where-is-voyager-1-now/06-03-voyager-2-card.jpg) *Voyager 2, the only spacecraft ever to visit Uranus and Neptune, is leaving below the plane of the planets. It crossed into interstellar space on 5 November 2018, six years after its twin.* ## The people who grew old talking to one machine Edward Stone was a 36-year-old physics professor in 1972 when he was asked to be chief scientist of a plan to send two spacecraft past the giant planets. He held the job for fifty years. He was there for Jupiter’s volcanic moon and Saturn’s braided rings, for Neptune in 1989, and for 25 August 2012, when Voyager 1 left the bubble of thin gas the Sun blows around itself and became the first human object between the stars. He retired in 2022 and died in June 2024, aged 88. His [successor, Linda Spilker](https://www.jpl.nasa.gov/news/edward-stone-retires-after-50-years-as-nasa-voyagers-project-scientist), first worked on Voyager in 1977. ![The pale moon Triton half lit in the foreground with blue Neptune and its faint rings behind](/media/where-is-voyager-1-now/06-10-triton-neptune.jpg) *Triton, with Neptune behind it. Voyager 2 flew past both on 25 August 1989 and found geysers on a surface at minus 235 degrees. No spacecraft has been back.* The team today is small, and some of it is very experienced indeed. It includes NASA retirees in their eighties. It also includes people who were born after the spacecraft left. In November 2023 they needed all of it. Voyager 1 began sending gibberish. It took months to trace the fault to a single dead memory chip in a computer built in the 1970s, and then to move the lost code, piece by piece, into other corners of its memory. Every test took 22 and a half hours to arrive and 22 and a half to answer. [In April 2024 the spacecraft made sense again](https://www.jpl.nasa.gov/news/nasas-voyager-1-resumes-sending-engineering-updates-to-earth/). ## A record that may never be played Bolted to the side of each Voyager is a gold-plated copper record, with a needle and drawn instructions for playing it. A committee led by the astronomer Carl Sagan decided what to put on it. They chose 115 pictures, greetings in 55 languages, the sound of surf and thunder and whales, and 90 minutes of music, from Bach to Chuck Berry. One track is an hour of a young woman’s brain waves and heartbeat, squeezed into a minute. She was Ann Druyan, the project’s creative director, and it was recorded two days after she and Sagan had decided, on the telephone, to get married. You can [stand beside the record as it is now](https://www.spaceradar.ai/#trip=strangest-things&stop=4), a day’s light from the nearest person who could put it on a turntable. **Fly there in the 3D map:** [Stand beside the record as it is now](https://www.spaceradar.ai/#trip=strangest-things&stop=4) ![The Voyager 1 spacecraft with Space Radar’s trip card about the gold record it carries](/media/where-is-voyager-1-now/06-08-golden-record.jpg) *The golden record rides on the side of the spacecraft’s ten-sided body, under an aluminium cover engraved with instructions for playing it.* Voyager took its own picture of the senders, once. On 14 February 1990, six billion kilometres out, it turned its camera back and photographed the planets it had left. The Earth came out as a point of light less than a pixel wide. Then the cameras were switched off for good, to save power. ## The rest of the far-flung fleet Five spacecraft are on their way out of the Solar System for good. The two Pioneers went first and fell silent long ago; the last faint word from Pioneer 10 came in January 2003. The newest is [New Horizons](https://www.spaceradar.ai/#at=deep-new-horizons), which crossed Pluto in 2015 after nine and a half years of flight and is now about 65 times the Earth’s distance from the Sun. It carries, on its upper deck, a small container of the ashes of Clyde Tombaugh, the man who found Pluto in 1930. ![Pluto and its large moon Charon side by side, half lit by a distant Sun](/media/where-is-voyager-1-now/06-09-pluto-charon.jpg) *Pluto and Charon, which circle each other. New Horizons took nine and a half years to reach them; sending all the pictures home took until October 2016.* Not everything far away was thrown. [The James Webb Space Telescope](https://www.spaceradar.ai/#at=deep-jwst) was [placed, very carefully](https://science.nasa.gov/mission/webb/orbit/), 1.5 million kilometres from the Earth on the side away from the Sun, about four times as far as the Moon. From there the Sun, the Earth and the Moon are all in the same direction, so one sunshield the size of a tennis court can hide all three and let the 6.5-metre mirror cool to 225 degrees below zero. Its launch was so accurate that it kept enough fuel to hold that spot for about twenty years. **Fly there in the 3D map:** [The James Webb Space Telescope](https://www.spaceradar.ai/#at=deep-jwst) ![Space Radar’s card for the James Webb Space Telescope beside a model of the telescope seen from its sunshield side](/media/where-is-voyager-1-now/06-05-webb-card.jpg) *How far is the James Webb telescope? Five light-seconds: 1.5 million km, or 0.010 AU on the map’s card. Unlike Hubble, it is far too distant for anyone to visit and repair.* And one thing was thrown purely for show. In February 2018 a new rocket needed a test load, and its builder used his own car. The red Roadster has been [circling the Sun ever since](https://www.spaceradar.ai/#at=tesla-roadster), once every 557 days, out past the orbit of Mars and back. In January 2025 astronomers announced a new asteroid, 2018 CN41, and deleted it less than a day later. It was the car. ![A red car seen from underneath, drifting among the stars, with Space Radar’s trip card and its speed and distance](/media/where-is-voyager-1-now/06-06-roadster.jpg) *In the glovebox: a towel and a copy of “The Hitchhiker’s Guide to the Galaxy”. On a circuit board: “Made on Earth by humans”. The map draws it where an orbit last measured in March 2018 says it should be.* ## What we will hear last Nobody knows the date. NASA’s own estimate is that the Voyagers may stay within reach of the big dishes until about 2036, if they still have the power to transmit. Dodd said last year that she was confident at least one of them could keep working for another two to five years. September 2027 will be Voyager 1’s fiftieth birthday. The last thing we hear will not be a discovery. It will most likely be a thin stream of housekeeping numbers, temperatures and voltages, from a machine with one instrument left on. Some day a scheduled call will go unanswered, and somebody will try again the next day. After that the spacecraft simply goes on. In about 300 years it reaches the inner edge of the cloud of comets that surrounds the Sun. In the year 40,272, by NASA’s reckoning, it passes within 1.7 light-years of a faint star in the Little Bear. The record will still be on its side. > The last thing we hear will not be a discovery. Open the map tonight, or [take the trip out past Jupiter to the farthest thing we sent](https://www.spaceradar.ai/#trip=outer-solar-system), and look at Voyager’s card. It said 17,929 days in space on the evening I wrote this. By the time you have read this sentence, the spacecraft is another hundred kilometres away. *Distances are as of October 2026 and change every second; the figures here come from NASA’s Jet Propulsion Laboratory and from Space Radar’s own live readings. Space Radar is a free, open-source live 3D map of everything in orbit and beyond. It runs in a browser at [spaceradar.ai](https://www.spaceradar.ai/), with no account.* **Fly there in the 3D map:** [Fly to Voyager 1](https://www.spaceradar.ai/#at=deep-voyager-1). Free, in your browser, no account. ## Questions people ask ### Where is Voyager 1 now? As of October 2026 it is about 25.8 billion km from the Earth, roughly 172 times the Earth’s distance from the Sun, in interstellar space. It reaches one light-day, 25.9 billion km, on 18 November 2026. ### Is Voyager 1 still working? Yes. As of 2026 it still sends data from its remaining instruments at 160 bits per second, and NASA hopes to keep at least one Voyager running into the 2030s. ### How far is the James Webb telescope from Earth? About 1.5 million km, four times the Moon’s distance, in orbit around a balance point called L2 on the side of the Earth away from the Sun. A radio signal takes five seconds to reach it. ### What is on the Voyager golden record? 115 images, spoken greetings in 55 languages, natural sounds and 90 minutes of music from many cultures, chosen in 1977 by a committee chaired by Carl Sagan. ## Sources 1. [The light bulb in a refrigerator](https://www.jpl.nasa.gov/images/pia17047-voyager-signal-spotted-by-earth-radio-telescopes/) 2. [Successor, Linda Spilker](https://www.jpl.nasa.gov/news/edward-stone-retires-after-50-years-as-nasa-voyagers-project-scientist) 3. [In April 2024 the spacecraft made sense again](https://www.jpl.nasa.gov/news/nasas-voyager-1-resumes-sending-engineering-updates-to-earth/) 4. [Placed, very carefully](https://science.nasa.gov/mission/webb/orbit/) 5. [Cp24.com: voyager 1 will reach one light day from earth in 2026 heres what that means](https://www.cp24.com/news/world/2025/12/09/voyager-1-will-reach-one-light-day-from-earth-in-2026-heres-what-that-means/) 6. [Science.nasa.gov: where are voyager 1 and voyager 2 now](https://science.nasa.gov/mission/voyager/where-are-voyager-1-and-voyager-2-now/) 7. [Science.nasa.gov: fact sheet](https://science.nasa.gov/mission/voyager/fact-sheet/) 8. [Science.nasa.gov: mission overview](https://science.nasa.gov/mission/voyager/mission-overview/) 9. [Science.nasa.gov: frequently asked questions](https://science.nasa.gov/mission/voyager/frequently-asked-questions/) 10. [Science.nasa.gov: did you know](https://science.nasa.gov/mission/voyager/did-you-know/) 11. [Science.nasa.gov: spacecraft](https://science.nasa.gov/mission/voyager/spacecraft/) 12. [Jpl.nasa.gov: nasas deep space antenna upgrades to affect voyager communications](https://www.jpl.nasa.gov/news/nasas-deep-space-antenna-upgrades-to-affect-voyager-communications/) 13. [Space.com: nasa commands voyager 2 probe interstellar space upgraded dsn](https://www.space.com/nasa-commands-voyager-2-probe-interstellar-space-upgraded-dsn) 14. [Skyatnightmagazine.com: voyager 2 low energy charged particle instrument switch off](https://www.skyatnightmagazine.com/news/voyager-2-low-energy-charged-particle-instrument-switch-off) 15. [Jpl.nasa.gov: ed stone former director of jpl and voyager project scientist dies](https://www.jpl.nasa.gov/news/ed-stone-former-director-of-jpl-and-voyager-project-scientist-dies) 16. [Science.nasa.gov: golden record contents](https://science.nasa.gov/mission/voyager/golden-record-contents/) 17. [Science.nasa.gov: greetings](https://science.nasa.gov/mission/voyager/golden-record-contents/greetings/) 18. [En.wikipedia.org: Contents of the Voyager Golden Record](https://en.wikipedia.org/wiki/Contents_of_the_Voyager_Golden_Record) 19. [Npr.org](https://www.npr.org/transcripts/123534818) 20. [Edition.cnn.com: nasa pluto new horizons clyde tombaugh ashes](https://edition.cnn.com/2015/07/13/us/nasa-pluto-new-horizons-clyde-tombaugh-ashes) 21. [Space.com: james webb space telescope fuel 20 years](https://www.space.com/james-webb-space-telescope-fuel-20-years) 22. [Esawebb.org: sun shield](https://esawebb.org/about/general/sun-shield) 23. [Astronomy.com: astronomers just deleted an asteroid because it turned out to be elon musks tesla roadster](https://www.astronomy.com/science/astronomers-just-deleted-an-asteroid-because-it-turned-out-to-be-elon-musks-tesla-roadster/) 24. [Spaceradar.ai](https://www.spaceradar.ai) --- # Where is the ISS right now? Two addresses in the sky > Ten people live off the planet this week, in exactly two homes. What their days are like, why the stations fly where they do, how to watch one cross your own street, and what happens when the bigger one comes down. By Ivan Akselrot. Published 2026-10-12. Category: Missions & Spacecraft. Tags: ISS, space stations, Tiangong, astronauts, orbit. 12 min read. Canonical: https://blog.spaceradar.ai/where-is-the-iss-right-now/ On the morning of 7 October 2026, four people closed a hatch, strapped themselves in and let go of their home. Their capsule, a SpaceX Dragon, backed slowly away from the International Space Station while both were travelling at about 28,000 kilometres an hour. NASA’s Jessica Meir and Jack Hathaway, the European Space Agency’s Sophie Adenot and the Russian cosmonaut Andrey Fedyaev were due to splash down off California the next day. Ask where the ISS is right now and the honest answer is “somewhere else already”: it covers about forty kilometres in the time it takes to read this sentence. But the question underneath is a better one. Once that capsule is down, seven people are left on the station. A little lower, and usually thousands of kilometres away, three more are spending an ordinary week on China’s Tiangong. That is the whole of humanity that is not on the Earth as I write: ten people, at two addresses. There has been at least one such address, with someone home, every day since 2 November 2000. This piece is about those two homes: what a day in them is like, why they fly where they do, how you can stand in your own street and watch one go over, and what it means that the larger of the two already has a demolition date. ## A six-bedroom house at eight kilometres a second Start with the larger one. NASA describes the station’s living space as bigger than a six-bedroom house: six sleeping quarters, two bathrooms, a gym and a bay window. The whole structure is 109 metres from end to end, one yard short of an American football field, and it has a mass of about 420 tonnes. Its first piece, a Russian-built module called Zarya, was launched on 20 November 1998. The first residents, Bill Shepherd, Yuri Gidzenko and Sergei Krikalev, moved in two years later and nobody has turned the lights off since. It flies between 370 and 460 kilometres up. That is a strangely modest number. London to Paris is about 340 kilometres; the station is roughly that far away, straight up. What makes it a spacecraft and not a very tall tower is the sideways speed: about eight kilometres a second, which would take you from London to New York in twelve minutes. At that pace it circles the planet roughly every ninety minutes, so the crew see sixteen sunrises and sixteen sunsets in every twenty-four hours. I have been watching both stations on Space Radar, a free live map of everything in orbit that draws each object where its published orbit says it is at that second. Open it and you can [follow the ISS live](https://www.spaceradar.ai/#at=sat-25544): its height, its speed, and a bar that shows whether it is in sunlight or in the Earth’s shadow, which flips twice on every lap. **Fly there in the 3D map:** [Follow the ISS live](https://www.spaceradar.ai/#at=sat-25544) ![A Space Radar screen showing the International Space Station with a card listing its height in kilometres, its speed and 93 minutes a lap](/media/where-is-the-iss-right-now/iss-live-card.jpg) *The station’s card on the live map. The height drifts by a few kilometres over each lap, because the orbit is not a perfect circle and the Earth is not a perfect sphere.* Life inside is organised around things the ground gives us for free. Water is the clearest example. In 2023 NASA reported that the station’s life-support system had reached [98 percent water recovery](https://www.nasa.gov/missions/station/iss-research/nasa-achieves-water-recovery-milestone-on-international-space-station/): sweat, breath and urine are collected, cleaned and drunk again. Gravity is the other. Without it, weight-bearing bones lose 1 to 1.5 percent of their mineral density a month, so every astronaut exercises for at least two hours a day, strapped to a treadmill or pulling against a machine that stands in for weight. - **98%** of the water on the station is recovered and reused, NASA reported in 2023. The crew’s drinking water has been through the crew before. Even bread is a problem. Crumbs do not fall; they drift into eyes and air filters. In November 1985 the Mexican astronaut Rodolfo Neri Vela asked for tortillas on his Space Shuttle flight, they made no crumbs, and they have been on the menu ever since. The bay window is real, too. It is called the Cupola, it was built in Europe and attached in 2010, and it has six windows around the sides and one on top that looks straight down at the planet. ## The smaller house, and the crack in its window The second address is newer and gets a fraction of the attention. Tiangong, which means “heavenly palace”, began with a core module launched on 29 April 2021. Two laboratory modules followed in 2022, and it has been permanently crewed since June of that year. Three people live there at a time, six for a few days when one crew hands over to the next. The current residents arrived on the Shenzhou-23 spacecraft on 24 May 2026: commander Zhu Yangzhu, Zhang Zhiyuan, and Lai Ka-ying, the first astronaut from Hong Kong. You can [see where Tiangong is at this moment](https://www.spaceradar.ai/#at=sat-48274) the same way as the ISS. **Fly there in the 3D map:** [See where Tiangong is at this moment](https://www.spaceradar.ai/#at=sat-48274) ![A Space Radar screen showing China’s Tiangong space station with a card listing its height, speed and minutes per lap](/media/where-is-the-iss-right-now/tiangong-live-card.jpg) *Tiangong on the same map, about forty kilometres lower than the ISS when these two pictures were taken. Its three modules were launched between April 2021 and October 2022.* Tiangong also supplied the most instructive scare of recent years. In November 2025 the crew of Shenzhou-20 were about to come home when tiny cracks were found in a window of their return capsule, most likely from a hit by a piece of space debris. Their return was delayed by more than a week. They finally landed on 14 November in the capsule that had brought their replacements, and China launched an empty spacecraft eleven days later so that the new crew would have a way home. Nobody was hurt. But it is worth holding on to the picture: a home with three people in it, and outside the window, at ten times the speed of a rifle bullet, other people’s rubbish. ![A Space Radar trip screen headed Two places, and only two: the Earth, mostly in night, with two labelled points close to its surface, the International Space Station and Tiangong](/media/where-is-the-iss-right-now/two-stations-one-planet.jpg) *Both stations in one frame, at the opening stop of the guided trip “Where people are living in space right now”. The moment was chosen because they were on the same side of the planet; most of the time they are thousands of kilometres apart.* That view opens a short guided trip on the map, [the two places where people are living in space right now](https://www.spaceradar.ai/#trip=people-in-space). It takes a minute and it is the fastest way I know to feel how thin the inhabited layer is. ## Why they fly where they do Neither station goes round the equator, and neither goes over the poles. The ISS orbit is tilted 51.6 degrees to the equator, and the reason is on the ground in Kazakhstan. The Russian Soyuz and Progress ships that serve the station launch from Baikonur. A rocket fired due east from there would drop its spent stages on China, so Russian launches aim further north, and 51.6 degrees is the lowest tilt they can reach directly. The station was put where both partners could get to it. The side effect is generous. A steeper tilt means a wider stripe of the planet passes underneath, and NASA says the station’s path covers [more than 90 percent of the world’s population](https://www.nasa.gov/international-space-station/space-station-facts-and-figures/). Tiangong, launched from further south, is tilted about 41.5 degrees, so it never passes directly overhead for anyone north of Rome or Chicago, though it can still be seen low in the sky from further north. ![A Space Radar screen: the Earth, mostly in night, with a thin white line around it showing the tilted path of the International Space Station’s orbit, marked at 30, 45 and 60 minutes ahead](/media/where-is-the-iss-right-now/iss-orbit-path.jpg) *The station’s next lap, with marks every fifteen minutes. Because the Earth turns underneath, each lap crosses the equator about 2,600 kilometres west of the one before.* The height is a compromise as well. Higher would mean thinner air, but a harder climb for every crew and cargo ship. Lower would mean thicker air. Even at 400 kilometres there is enough of it to slow the station down, so it sinks, and a docked ship regularly fires its engines to push it back up. NASA’s own estimate is that without those boosts the station would stay up for only a year or two. You can feel the scale of this by going straight up from wherever you are. There is a trip on the map that does exactly that: [from your ground to the space station](https://www.spaceradar.ai/#trip=journey-to-the-station), through the twelve kilometres where the weather is, past the line at a hundred kilometres where space officially begins, and on to the station and its next pass over you. **Fly there in the 3D map:** [From your ground to the space station](https://www.spaceradar.ai/#trip=journey-to-the-station) ## How to watch a house go over your street Here is the part that surprises people: you do not need a telescope, or binoculars, or dark skies. NASA’s own description is that the station looks like [an airplane or a very bright star](https://www.nasa.gov/spot-the-station/), except that it has no flashing lights and does not change direction. At its best it rivals Venus. The catch is timing. The station has no lights of its own that you could see; you are looking at sunlight on its solar panels. So it is only visible when it is in sunshine and you are in the dark, which means the few hours after sunset and the few hours before sunrise. A good pass lasts about six minutes. It rises on one side of the sky, climbs, and often fades out in mid-air before it reaches the far horizon, as it slips into the Earth’s shadow. ![The dawn sky from London with constellation lines above a dark horizon and a curved line showing the path of the International Space Station across it](/media/where-is-the-iss-right-now/station-pass-en.jpg) *A pass of the ISS over London, as the map computes it for the morning of 18 October 2026: up in the south-west at 06:16, 36 degrees high at 06:19, gone in the east by 06:22. The map marks predictions this far ahead as rougher.* On the map, the “Tonight” view shows [the sky from your own street](https://www.spaceradar.ai/#trip=tonight-from-your-street) with the passes worked out for the place you choose. Pick the next bright one, go outside five minutes early, and look where it tells you. A steady light that does not blink, moving faster than any plane at cruising height appears to: that is seven people. ## The house with a demolition date The station’s oldest modules have been in orbit since 1998, and a structure that swings from sunlight to shadow sixteen times a day does not last for ever. NASA plans to operate it until 2030, and in June 2024 it gave SpaceX a contract worth up to 843 million dollars to build [the vehicle that will bring it down](https://www.nasa.gov/news-release/nasa-selects-international-space-station-us-deorbit-vehicle/): a tug that docks, waits, and then pushes 420 tonnes out of orbit on purpose. Russia has committed to the partnership through at least 2028. Something that size does not burn up completely, so it has to be aimed. The usual target for large spacecraft is the emptiest stretch of the South Pacific, around a spot called Point Nemo, which is about 2,688 kilometres from the nearest land. Mir, the last great Russian station, came down over the Pacific on 23 March 2001; people in Fiji watched the pieces go over. On the map, the trip about satellites and junk ends by flying to [the place where spacecraft come down](https://www.spaceradar.ai/#trip=satellites-and-junk&stop=8). ![The Pacific Ocean filling the face of the Earth, with almost no land in view and hundreds of satellite markers over it](/media/where-is-the-iss-right-now/point-nemo.jpg) *The South Pacific, with New Zealand at the left edge and the tip of South America at the right. Point Nemo, in the middle, is about 2,688 kilometres from the nearest land. Each dot is a working satellite passing over.* What comes after is less settled than the plan suggests. Several companies are building private stations, but as of October 2026 none of them is flying; the first, a single-module outpost called Haven-1, is not expected to launch before 2027. Some United States senators want the ISS kept until 2032 and not brought down until a successor is working. If the timetable holds and the successors slip, there could be a stretch in the 2030s when the only address in the sky is the Chinese one. ## Nobody under twenty-six Go back to the date. The first crew launched on 31 October 2000 and opened the hatch on 2 November. NASA marked twenty-five years of continuous human presence on 2 November 2025. There has been no gap. > Anyone younger than twenty-six has never lived a single day on a planet with everybody on it. It is a small club up there. Fewer than eight hundred people have ever flown above a hundred kilometres; more than 290 of them, from 26 countries, have visited the ISS. The largest number ever in orbit at one moment is nineteen. For almost everyone, the closest we will get is the view from the pavement. So take it. Find out when the next pass is over your town. Go out a few minutes early, let your eyes settle, and face the direction you were given. When a bright, steady light climbs out of the rooftops and sails across without a sound, remember what it is: a house, with the lights of the Sun on it, and people inside who are probably having dinner. > **About Space Radar.** Space Radar is a free, open-source live 3D map of everything in orbit: satellites, stations, debris, rockets, planets and stars, each at its real, computed position. It runs in the browser with no account at [spaceradar.ai](https://www.spaceradar.ai/). **Fly there in the 3D map:** [Who is in space right now](https://www.spaceradar.ai/#trip=people-in-space). Free, in your browser, no account. ## Questions people ask ### How many people are in space right now? As of the second week of October 2026, ten: seven on the International Space Station and three on China’s Tiangong. It rises for a few days whenever crews hand over. ### Where is the ISS right now? It is 370 to 460 kilometres above the Earth and circles the planet about every ninety minutes, so its position changes by roughly eight kilometres every second. A live ISS tracker computes the spot from its published orbit. ### Can I see the ISS without a telescope? Yes. It looks like a very bright star moving steadily across the sky, with no flashing lights. It is visible for a few minutes at a time in the hours after sunset or before sunrise, when it is in sunlight and you are in the dark. ### When will the ISS be brought down? NASA plans to operate the station until 2030 and then steer it into a remote part of the ocean using a vehicle built by SpaceX. The exact date depends on its partners and on whether commercial stations are ready. ## Sources 1. [An airplane or a very bright star](https://www.nasa.gov/spot-the-station/) 2. [More than 90 percent of the world’s population](https://www.nasa.gov/international-space-station/space-station-facts-and-figures/) 3. [98 percent water recovery](https://www.nasa.gov/missions/station/iss-research/nasa-achieves-water-recovery-milestone-on-international-space-station/) 4. [The vehicle that will bring it down](https://www.nasa.gov/news-release/nasa-selects-international-space-station-us-deorbit-vehicle/) 5. [Nasa.gov: nasas spacex crew 12 undocks in dragon for ride home](https://www.nasa.gov/blogs/spacestation/2026/10/07/nasas-spacex-crew-12-undocks-in-dragon-for-ride-home/) 6. [Nasa.gov: crew 12 ready to depart as new residents begin advanced health research](https://www.nasa.gov/blogs/spacestation/2026/10/06/crew-12-ready-to-depart-as-new-residents-begin-advanced-health-research/) 7. [Nasa.gov: expedition 75](https://www.nasa.gov/mission/expedition-75/) 8. [Cmse.gov.cn](https://www.cmse.gov.cn/) 9. [En.wikipedia.org: Shenzhou 23](https://en.wikipedia.org/wiki/Shenzhou_23) 10. [Nasa.gov: expedition 1](https://www.nasa.gov/mission/expedition-1/) 11. [Nasa.gov: the international space station marks 25 years of continuous human presence](https://www.nasa.gov/centers-and-facilities/johnson/the-international-space-station-marks-25-years-of-continuous-human-presence/) 12. [Nasa.gov: zarya module](https://www.nasa.gov/international-space-station/zarya-module/) 13. [Nasa.gov: international space station](https://www.nasa.gov/reference/international-space-station/) 14. [Nasa.gov: the human body in space](https://www.nasa.gov/humans-in-space/the-human-body-in-space/) 15. [Nasa.gov: space station 20th food on iss](https://www.nasa.gov/history/space-station-20th-food-on-iss/) 16. [Esa.int: Cupola](https://www.esa.int/Science_Exploration/Human_and_Robotic_Exploration/International_Space_Station/Cupola) 17. [En.wikipedia.org: Tiangong space station](https://en.wikipedia.org/wiki/Tiangong_space_station) 18. [Ria.ru: kitay 2094450970](https://ria.ru/20260524/kitay-2094450970.html) 19. [Pbs.org: chinese astronauts return from space station after delay blamed on space debris damage](https://www.pbs.org/newshour/science/chinese-astronauts-return-from-space-station-after-delay-blamed-on-space-debris-damage) 20. [Spacenews.com: shenzhou 22 docks at tiangong space station resolving human spaceflight emergency](https://spacenews.com/shenzhou-22-docks-at-tiangong-space-station-resolving-human-spaceflight-emergency/) 21. [Orbitaldebris.jsc.nasa.gov: faq](https://orbitaldebris.jsc.nasa.gov/faq/) 22. [Spaceflight.nasa.gov](https://spaceflight.nasa.gov/feedback/expert/answer/mcc/sts-112/09_04_12_54_17.html) 23. [Nasa.gov: faqs the international space station transition plan](https://www.nasa.gov/faqs-the-international-space-station-transition-plan/) 24. [Nasa.gov: spot the space station over your backyard with new nasa service](https://www.nasa.gov/news-release/spot-the-space-station-over-your-backyard-with-new-nasa-service/) 25. [Oceanservice.noaa.gov: nemo](https://oceanservice.noaa.gov/facts/nemo.html) 26. [Nasa.gov: 20 years ago space station mir reenters earths atmosphere](https://www.nasa.gov/history/20-years-ago-space-station-mir-reenters-earths-atmosphere/) 27. [Payloadspace.com: vast delays haven 1 launch to 2027](https://payloadspace.com/vast-delays-haven-1-launch-to-2027/) 28. [Scientificamerican.com: nasa must delay deorbiting the iss u s lawmakers say](https://www.scientificamerican.com/article/nasa-must-delay-deorbiting-the-iss-u-s-lawmakers-say/) 29. [En.wikipedia.org: Astronaut](https://en.wikipedia.org/wiki/Astronaut) 30. [Nasa.gov: space station visitors by country](https://www.nasa.gov/international-space-station/space-station-visitors-by-country/) --- # How many satellites are in orbit? The junkyard above us > About seventeen thousand working machines, and at least as many dead ones, share the space a few hundred kilometres over your head. How it filled up in one lifetime, who keeps the list, what a collision looks like, and why it reaches your weather forecast. By Ivan Akselrot. Published 2026-10-09. Category: Earth & Orbit. Tags: space debris, satellites, Kessler syndrome, Starlink, collisions. 12 min read. Canonical: https://blog.spaceradar.ai/how-many-satellites-in-orbit/ At 16:56 Greenwich time on 10 February 2009, about 790 kilometres above northern Siberia, a working American telephone satellite and a dead Russian communications satellite arrived at the same point in space. Iridium 33 weighed 560 kilograms and Cosmos 2251 about 900. They met at more than eleven kilometres a second. Nobody saw it. What radar found afterwards was two clouds. In time, more than 2,300 pieces of the pair were large enough to be tracked and given catalogue numbers, and a great many of them are still up. It is a useful thing to have in mind when you ask how many satellites are in orbit, because the honest answer comes in three parts: the ones that work, the ones that do not, and the pieces. This is a story about a place most of us never think of as a place. In sixty-nine years the thin shell of space just above the weather has gone from empty to crowded, with traffic, wrecks, a rubbish problem and no caretaker. It matters to you even if you have no interest in space at all, because the machines that tell you whether to take an umbrella fly through the worst of it. ## Sixty-nine years, from one to forty-seven thousand On 4 October 1957 there was one: Sputnik 1. A small American satellite, Vanguard 1, went up on 17 March 1958 and never came down. It is the oldest human-made thing still in orbit, sixty-eight years of laps and counting. It took less than four years to break something. On 29 June 1961, seventy-seven minutes after reaching orbit, the upper stage of an American rocket broke apart. NASA’s history of such events calls it the first known satellite fragmentation. It left 317 pieces big enough to catalogue, and 193 of them were still in orbit six decades later. Since then, by the European Space Agency’s [running count](https://sdup.esoc.esa.int/discosweb/statistics/) (as of July 2026), about 7,320 launches have placed about 27,490 satellites in orbit. Roughly 18,850 are still up there. About 15,900 still work. The total mass of everything human-made in orbit is more than 17,000 tonnes, forty International Space Stations’ worth. I have been looking at all this through Space Radar, a free live map of everything in orbit that draws each object where its published orbit puts it. It also counts. Working from the public catalogue as it stood on 6 October 2026, the map found 34,570 objects, and 17,450 of them were no longer doing a job: 12,347 fragments, 2,858 dead satellites and 2,245 spent rocket bodies. - **1 in 2** of the objects in the public catalogue no longer works: 17,450 of 34,570, counted by Space Radar from CelesTrak’s catalogue on 6 October 2026. ![A Space Radar panel headed with the count of tracked objects that no longer work, listing pieces of debris, spent rocket bodies, dead satellites and working satellites, beside the Earth covered in grey dots](/media/how-many-satellites-in-orbit/debris-by-the-numbers.jpg) *The map’s own tally, by kind and by height. Radar can follow things down to roughly ten centimetres across in low orbit; anything smaller is in no catalogue.* You can take the tour yourself. The guided trip [Satellites and space junk](https://www.spaceradar.ai/#trip=satellites-and-junk) starts with one station, switches on every working satellite, and then switches on the rest. **Fly there in the 3D map:** [Satellites and space junk](https://www.spaceradar.ai/#trip=satellites-and-junk) ## The people who keep the list Somebody has to know where all of it is. The main catalogue is kept by the United States Space Force: the 18th Space Defense Squadron, at Vandenberg in California, follows more than 47,000 objects with a worldwide network of radars and telescopes and publishes most of their orbits. T. S. Kelso republishes that data through a site called CelesTrak, in a form anyone can use. That openness is why a free map can exist at all. The list has two blind spots. The first is that not everything tracked is published: about 47,000 objects are followed, but the public catalogue I counted from holds about 35,000. The second is size. From the ground, radar loses things smaller than about ten centimetres in low orbit, and smaller than about a metre in the high orbits. What it cannot see is most of it. The European Space Agency’s model puts the number of pieces between one and ten centimetres at 1.5 million, and those between a millimetre and a centimetre at 230 million. These are estimates, not counts. But the evidence for them arrives regularly. In 2016 the astronaut Tim Peake photographed a seven-millimetre chip in a window of the space station’s observation dome. The agency’s best guess at the culprit was a flake of paint, or a metal fragment a few thousandths of a millimetre across. In November 2025 the return of three Chinese astronauts was delayed by more than a week after tiny cracks were found in a window of their capsule, most likely from a debris strike. ![A Space Radar trip screen headed The crowded shell: Europe at night with its city lights, and satellite markers scattered across it](/media/how-many-satellites-in-orbit/crowded-shell.jpg) *The low shell over Europe at night. Down here a satellite circles the Earth in about ninety minutes, and anything crossing its path does so at several kilometres a second.* That is the arithmetic of the low shell, and you can [fly down into the crowded part](https://www.spaceradar.ai/#trip=satellites-and-junk&stop=3) to see it. Everything is moving at seven or eight kilometres a second, in different directions, so the average impact comes at about ten, according to NASA. At that speed a fleck of paint is a bullet and a bolt is a bomb. **Fly there in the 3D map:** [Fly down into the crowded part](https://www.spaceradar.ai/#trip=satellites-and-junk&stop=3) ## What a collision looks like The first known accident between two catalogued objects came on 24 July 1996. A small French satellite called Cerise was hit by a fragment of a European rocket stage that had broken up ten years earlier. The closing speed was 14.8 kilometres a second, and it knocked off a single piece large enough to track. The worst single event was not an accident. On 11 January 2007 China destroyed one of its own old weather satellites, Fengyun-1C, with a missile, about 860 kilometres up. NASA eventually catalogued 3,532 fragments. The European Space Agency reckons the test raised the number of trackable objects in orbit by a quarter in a single event. At that height the air is too thin to clear the wreckage quickly: by the map’s count, 2,314 pieces of that one satellite were still circling in October 2026. Then came 2009, the crash this story began with: 2,371 catalogued fragments from two satellites, one of them working. And on 15 November 2021 Russia destroyed its own defunct Cosmos 1408 in another missile test, adding 1,760 tracked pieces, at a height not far above the International Space Station. The crew were told to shelter in their return capsules. NASA’s administrator at the time, Bill Nelson, said he was [“outraged by this irresponsible and destabilizing action”](https://www.nasa.gov/news-release/nasa-administrator-statement-on-russian-asat-test/). > By April 2025 the space station had fired its engines 41 times to get out of the way of debris. The station is the most protected thing in orbit and it still has to duck. NASA counts 41 avoidance manoeuvres since 1999. You can [follow the ISS](https://www.spaceradar.ai/#at=sat-25544) on the map and watch it do its ninety-minute lap through the same shell. **Fly there in the 3D map:** [Follow the ISS](https://www.spaceradar.ai/#at=sat-25544) ![A Space Radar trip screen headed A dead satellite: a model of Envisat among satellite markers above the Earth, with a card giving its height, 791 kilometres](/media/how-many-satellites-in-orbit/envisat-dead-satellite.jpg) *Envisat, an eight-tonne European environment satellite, some 770 to 790 kilometres up. Contact was lost on 8 April 2012 and it has circled, uncontrolled, ever since.* Not all of the danger is small. [Envisat](https://www.spaceradar.ai/#at=sat-27386) is an eight-tonne European environment satellite, one of the largest Earth-watching machines ever flown. On 8 April 2012 it stopped answering, and it has been going round ever since with nobody at the controls. ## Kessler’s arithmetic In 1978 two NASA scientists, Donald Kessler and Burton Cour-Palais, published a paper with a dry title and an alarming subtitle: [“Collision Frequency of Artificial Satellites: The Creation of a Debris Belt”](https://doi.org/10.1029/JA083iA06p02637). Their point was simple. Every collision makes fragments. Every fragment is a new thing that can collide. Past a certain crowding, the fragments are made faster than the atmosphere can drag them down, and the population grows by itself, even if nobody launches anything again. A colleague later named this the Kessler syndrome, and films have turned it into a chain reaction that wipes out everything in an afternoon. The real version is slower and, in a way, worse: a process of decades that is hard to notice and impossible to reverse. Kessler has since written that the debris environment is already “unstable”. The European Space Agency’s [2026 report on the space environment](https://www.esa.int/Space_Safety/Space_Debris/ESA_Space_Environment_Report_2026) says it without drama: even with no further launches, collisions among the debris already present are expected to make the population in low orbit keep growing. ![The Earth from far away, hidden inside a ball of low satellites, with arcs of points at the edges of the frame that belong to the geostationary ring](/media/how-many-satellites-in-orbit/geostationary-ring.jpg) *From far away the low satellites hide the planet. The arcs of points at the edges of the frame are the geostationary ring, nearly 36,000 kilometres up, where a satellite keeps pace with the turning Earth. Nothing up here ever falls down; dead satellites are pushed a few hundred kilometres higher and left.* Height decides how long a mistake lasts. In the lowest orbits the air cleans up within a few years. Around 850 kilometres, nearly two decades have removed only about a third of the catalogued Fengyun wreckage. And in [the ring that stands still](https://www.spaceradar.ai/#trip=satellites-and-junk&stop=4), almost 36,000 kilometres up, where television and weather satellites sit, nothing ever comes down at all. ## Eleven thousand of one kind Now add the newest fact, which is that the sky has a majority owner. As of 30 September 2026, the astronomer Jonathan McDowell, who keeps [a widely used independent tally](https://planet4589.org/space/stats/active.html), counted 16,913 working satellites. Of those, 11,143 belong to a single internet network, Starlink. That is two out of every three. The first sixty of them went up in May 2019. Other fleets are following, among them Amazon’s Kuiper and China’s Qianfan, each with a few hundred satellites up so far. In 2025 alone, more than 300 launches put over 4,000 new satellites into orbit. The operators are not careless; they have every reason not to be. Starlink satellites fly low, so that a dead one falls out of the sky by itself, and they are built to dodge without waiting for a human. But look at what the dodging amounts to. In its latest half-yearly report to the United States regulator, SpaceX said its satellites had made 207,152 collision-avoidance manoeuvres between December 2025 and May 2026. - **Every 76 seconds** on average, a Starlink satellite changed course to avoid something, according to SpaceX’s report for the six months to May 2026. ## Who cleans up Mostly, the air does. More than three intact satellites or rocket stages fall back into the atmosphere every day, the European agency reports, about 1,200 in 2025. Some are steered into the emptiest part of the South Pacific. Most simply burn up on the way down. ![A Space Radar trip screen headed A spent rocket: a model of a rocket upper stage above the Earth among satellite markers](/media/how-many-satellites-in-orbit/spent-rocket.jpg) *A spent rocket stage, one of more than 2,000 in the catalogue. Stages like this are large and uncontrolled; the first break-up in orbit, in 1961, was one of them.* The rules are tightening. For years the guideline was to remove a satellite within twenty-five years of the end of its work; European missions must now do it within five, and the United States regulator adopted a five-year rule in 2022. In October 2023 it issued the first fine for breaking a debris promise: 150,000 dollars, to a television company that had left an old satellite in the wrong place. More than 200 organisations have signed a European “Zero Debris” charter. As for actually collecting the rubbish, we are at the stage of proving it can be approached. In November 2024 a Japanese spacecraft called ADRAS-J flew to within about fifteen metres of [a spent rocket stage](https://www.spaceradar.ai/#trip=satellites-and-junk&stop=7), close enough to inspect it. A European mission to grab and remove a small old satellite is planned for 2029. No piece of old junk has yet been brought down by a clean-up mission. ## The forecast Here is why it comes back to the umbrella. The European weather centre in Reading uses about 60 million observations a day to start its forecasts, and most of them come from around ninety instruments on satellites. Many of the most valuable ones ride on satellites that pass over the poles a little above 800 kilometres. That is the same band as the Chinese missile test and the 2009 crash. The forecast flies through the wreckage. ![The evening sky from London with constellation lines above a dark horizon, beside a list of satellites that will pass over tonight](/media/how-many-satellites-in-orbit/tonight-passes-en.jpg) *An evening sky over London with the satellites that will cross it. On a clear night, away from street lamps, a patient watcher can count several in an hour.* So go and look at it. On a clear evening, an hour after sunset, stand somewhere dark for ten minutes and watch for points of light that move steadily and do not blink. Each one is a machine, or the shell of one. The map will show you [which satellites cross your own sky tonight](https://www.spaceradar.ai/#trip=tonight-from-your-street). And somewhere among the ones too faint to see is Vanguard 1, still on its laps, sixty-eight years after someone let it go. > **About Space Radar.** Space Radar is a free, open-source live 3D map of everything in orbit: satellites, stations, debris, rockets, planets and stars, each at its real, computed position. It runs in the browser with no account at [spaceradar.ai](https://www.spaceradar.ai/). **Fly there in the 3D map:** [Fly through the satellites and the junk](https://www.spaceradar.ai/#trip=satellites-and-junk). Free, in your browser, no account. ## Questions people ask ### How many satellites are in orbit right now? About 16,900 working satellites as of 30 September 2026, by Jonathan McDowell’s count, and close to 19,000 or 20,000 if you include the dead ones still circling. Two thirds of the working ones belong to Starlink. ### How much space debris is there? Space surveillance networks follow about 47,000 objects, and roughly half of those in the public catalogue no longer work. The European Space Agency’s model adds about 1.5 million pieces between one and ten centimetres that are too small to track. ### What is the Kessler syndrome? It is the point at which collisions create fragments faster than the atmosphere removes them, so the debris keeps growing by itself. Donald Kessler and Burton Cour-Palais described it in 1978; it is a slow process of decades, not a sudden chain reaction. ### Does space debris fall on people? More than three intact satellites or rocket stages re-enter every day, and most of the material burns up. The largest spacecraft are steered into a remote part of the South Pacific. ## Sources 1. [Running count](https://sdup.esoc.esa.int/discosweb/statistics/) 2. [“outraged by this irresponsible and destabilizing action”](https://www.nasa.gov/news-release/nasa-administrator-statement-on-russian-asat-test/) 3. [“Collision Frequency of Artificial Satellites: The Creation of a Debris Belt”](https://doi.org/10.1029/JA083iA06p02637) 4. [2026 report on the space environment](https://www.esa.int/Space_Safety/Space_Debris/ESA_Space_Environment_Report_2026) 5. [A widely used independent tally](https://planet4589.org/space/stats/active.html) 6. [Orbitaldebris.jsc.nasa.gov: ODQNv13i2.pdf](https://orbitaldebris.jsc.nasa.gov/quarterly-news/pdfs/ODQNv13i2.pdf) 7. [Orbitaldebris.jsc.nasa.gov: HOOSF 16e.pdf](https://orbitaldebris.jsc.nasa.gov/library/HOOSF_16e.pdf) 8. [Esa.int: About space debris](https://www.esa.int/Space_Safety/Space_Debris/About_space_debris) 9. [Space-track.org: documentation](https://www.space-track.org/documentation) 10. [Esa.int: Impact chip](https://www.esa.int/ESA_Multimedia/Images/2016/05/Impact_chip) 11. [Pbs.org: chinese astronauts return from space station after delay blamed on space debris damage](https://www.pbs.org/newshour/science/chinese-astronauts-return-from-space-station-after-delay-blamed-on-space-debris-damage) 12. [Orbitaldebris.jsc.nasa.gov: faq](https://orbitaldebris.jsc.nasa.gov/faq/) 13. [Aquarid.physics.uwo.ca: KesSym](https://aquarid.physics.uwo.ca/kessler/KesSym.html) 14. [Sdo.esoc.esa.int: Space Environment Report I10R0 20260501.pdf](https://www.sdo.esoc.esa.int/publications/Space_Environment_Report_I10R0_20260501.pdf) 15. [Api-prod.fcc.gov: bff0244acfb947505791bf252f851ce6](https://api-prod.fcc.gov/icfs-attachment/exp/api/v1/bff0244acfb947505791bf252f851ce6) 16. [Esa.int: Mitigating space debris generation](https://www.esa.int/Space_Safety/Space_Debris/Mitigating_space_debris_generation) 17. [Docs.fcc.gov: DOC 397412A1.pdf](https://docs.fcc.gov/public/attachments/DOC-397412A1.pdf) 18. [Blogs.esa.int: spacesafety community](https://blogs.esa.int/spacesafety-community/?p=1054) 19. [Esa.int: ClearSpace 1](https://www.esa.int/Space_Safety/ClearSpace-1) 20. [Ecmwf.int](https://www.ecmwf.int/node/38367) --- # What do satellites do? The machines you used before breakfast > The time on your phone, the dot on the map, the weather icon, the bread on the table: an ordinary morning leans on a few hundred quiet machines that almost nobody thinks about. Where they are, how they work, and how easily they could be taken away. By Ivan Akselrot. Published 2026-10-07. Category: Earth & Orbit. Tags: satellites, GPS, weather satellites, navigation, Galileo. 11 min read. Canonical: https://blog.spaceradar.ai/what-do-satellites-do/ Picture an ordinary Tuesday in Leeds. At 06:30 a phone on a bedside table lights up and plays a sound. Its owner squints at a small cloud with two raindrops under it, decides against the bicycle, and checks that the 07:12 bus is four minutes away. In the kitchen there is toast. On the way out she looks at the map once more, and the bus is a small moving dot two streets away. She has not thought about space once. Ask what satellites do, and most people say television, or spying, or something to do with rockets. But before breakfast this woman has used an atomic clock orbiting 20,000 kilometres up, a camera parked over the equator, another that skims over the poles, and very probably a tractor that steers itself by signals from the sky. That gap between how much we lean on these machines and how little we notice them is the subject of this piece. In a survey of 20,000 people in eleven countries, carried out for the satellite operator Inmarsat in 2022, only eight percent connected space with communications at all. So here is the morning again, slowly, with the machines put back in: where they are, how they do it, and how sturdy the whole arrangement really is. ## The clock in the sky Begin with the time on the phone, because it is the least understood. The Global Positioning System is usually described as a way of finding where you are. It is better understood as about thirty-one very good clocks, flying in six rings at about 20,200 kilometres, each one telling anyone who will listen what time it is and where it was when it said so. Your phone does the rest. A signal from a satellite takes a moment to arrive, and the length of that moment is a distance. Hear four satellites and the phone can solve for four unknowns: where you are in three dimensions, and what time it really is. The system is arranged so that at least four are in view from almost anywhere on the planet. It is run by a single unit of the United States Space Force, the 2nd Space Operations Squadron, from a base in Colorado, and since May 2000, when a deliberate blurring of the civilian signal was switched off, it has been both accurate and free. I looked for these satellites on Space Radar, a free live map of everything in orbit that draws each object where its published orbit puts it. Its standing view carries Europe’s twin of GPS, which works the same way: [here is one of the Galileo navigation satellites](https://www.spaceradar.ai/#at=sat-37846), about 23,000 kilometres up and fourteen hours to a lap, far above the crowded low orbits. **Fly there in the 3D map:** [Here is one of the Galileo navigation satellites](https://www.spaceradar.ai/#at=sat-37846) ![A Space Radar screen showing a Galileo navigation satellite far from the Earth with a card giving its height, 23,237 kilometres, and its speed](/media/what-do-satellites-do/galileo-satellite.jpg) *One of Europe’s Galileo navigation satellites. From this height the whole planet is a small disc, which is why a few dozen satellites are enough to cover it.* The accuracy this takes is hard to hold in the head. Light travels about thirty centimetres in a billionth of a second, so a clock that is wrong by one billionth of a second puts you thirty centimetres off. And the clocks do not even run at the same rate as ours. They are moving fast, which by Einstein’s special relativity slows them, and they are high in the Earth’s gravity, which by general relativity speeds them up. The second effect wins. - **38 millionths of a second** is how much a GPS satellite’s clock gains on a clock on the ground every day. Left uncorrected, the error in your position would grow by about eleven kilometres a day. The engineers who built the system set the satellite clocks to tick slightly slow on the ground so that they would be right in orbit. Every blue dot on every map is a small daily confirmation that Einstein was correct. ## Time is the real product Here is the part that surprised me most. For much of the economy the useful thing about GPS is not the position at all. It is the time. The United States government’s own description is blunt: communication systems, electrical power grids and financial networks [all rely on precision timing](https://archive.gps.gov/applications/timing/), and mobile networks use GPS time to keep all of their base stations in step. That is the bedside phone: it knows the time because the mast it talks to is listening to the sky. It is the stock market too. American brokers are required to stamp their trades with clocks held within fifty thousandths of a second of the official national time, and a receiver on the roof listening to the same satellites is a standard way to do it. We know what happens when the time is wrong, because it has been. In January 2016, while an old GPS satellite was being retired, a software error left fifteen others broadcasting a time signal that was off by thirteen millionths of a second. Thirteen millionths. Timing equipment around the world raised alarms for hours. A study commissioned by the American standards institute, NIST, put a number on the dependence in 2019: a loss of GPS would cost the United States economy [about a billion dollars a day](https://www.nist.gov/news-events/news/2019/10/economic-benefits-global-positioning-system-us-private-sector-study). A British government estimate in 2025 was 1.4 billion pounds for a single day. ## The picture of the weather Now the little cloud. On 1 April 1960 the United States launched TIROS-1, the first weather satellite. It worked for 78 days and sent back more than 19,000 usable pictures, and nobody who forecasts the weather has been willing to go without since. Today’s picture comes from two kinds of machine. The first kind sits in a ring about 35,800 kilometres above the equator, where one lap takes exactly one day, so the satellite hangs over the same spot. From there a camera sees a whole face of the planet at once. Europe and Africa are watched by [Meteosat-12](https://www.spaceradar.ai/#at=sat-54743&t=2026-10-08T11:00:00Z), which went into service in December 2024 and scans the full disc every ten minutes. The Americas are watched by [GOES-19](https://www.spaceradar.ai/#at=sat-60133), which took over the eastern slot in April 2025. **Fly there in the 3D map:** [Meteosat-12](https://www.spaceradar.ai/#at=sat-54743&t=2026-10-08T11:00:00Z) ![A Space Radar trip screen headed The ring that stands still: the Earth from far away, wrapped in a ball of low satellites, with scattered points much farther out](/media/what-do-satellites-do/geostationary-weather-ring.jpg) *From far enough away the low satellites become a ball around the planet. The scattered points far outside it are the high ones, and the ring that stands still is among them: weather satellites share it with television and communications satellites.* ![A Space Radar screen showing the Meteosat-12 weather satellite high above Africa and Europe with a card giving its height](/media/what-do-satellites-do/meteosat-12.jpg) *Meteosat-12, Europe’s newest weather eye, about 36,000 kilometres above the Gulf of Guinea. Its view takes in Africa, Europe and the Atlantic in one frame.* The second kind flies low, over the poles, about fourteen laps a day, while the planet turns underneath, so that it sees every place on Earth twice a day from close up. These are the ones that measure temperature and moisture through the depth of the air, and forecasters prize them at least as much as the pictures. The European forecasting centre in Reading receives around 800 million observations a day and uses about 60 million of them, most from some ninety instruments on satellites. What all this bought is easy to state. Forecasts have improved by about one day per decade: a six-day forecast is now as good as a five-day forecast was ten years earlier, a result set out in a much-cited paper in [Nature in 2015](https://doi.org/10.1038/nature14956). The cloud-and-raindrops icon is the output of a planet-sized measuring instrument, and you looked at it for under a second. ![The Earth seen over the Pacific Ocean with the day’s cloud patterns and a small spiral storm off the coast of Mexico](/media/what-do-satellites-do/todays-weather.jpg) *The day’s real clouds over the eastern Pacific, from the guided trip “The living Earth”. The tight white swirl off Mexico is a tropical storm.* You can see the same thing a forecaster starts from. The trip called “The living Earth” on the map stops at [the day’s weather, drawn from real satellite data](https://www.spaceradar.ai/#trip=the-living-earth&stop=4): cloud, storms and the winds between them. **Fly there in the 3D map:** [The day’s weather, drawn from real satellite data](https://www.spaceradar.ai/#trip=the-living-earth&stop=4) ## The field, the ship and the beacon The toast has a satellite in it as well. Landsat, a programme that began in July 1972, has photographed the land surface of the whole planet ever since. Its newest member, [Landsat 9](https://www.spaceradar.ai/#at=sat-49260), flies 705 kilometres up and comes back over the same field every sixteen days; with its twin, every eight. Each pixel is thirty metres across, and the pictures are free. A grower can see which corner of a field is thirsty before it shows from the gate. ![A Space Radar screen showing the Landsat 9 Earth-observation satellite above the Earth with a card giving its height and speed](/media/what-do-satellites-do/landsat-9.jpg) *Landsat 9, launched on 27 September 2021. It crosses the equator at the same local time on every lap, so the light in its pictures is always comparable.* Then the tractor drives itself along the rows. By the American agriculture department’s figures, automatic steering guided by satellite was already used on more than half of the country’s maize and soya-bean land by 2016 to 2018, and on around seventy percent of the largest farms. Less overlap, less fuel, less fertiliser. The pattern repeats wherever things move. Every ship of 300 gross tons or more on an international voyage must carry a transponder that broadcasts who and where it is, and more than 80 percent of the world’s trade by volume goes by sea. The parcel you are waiting for is, somewhere, a dot. And then there is the service you hope never to use. Since 1982 an international system called Cospas-Sarsat has listened from orbit for distress beacons from boats, aircraft and walkers. Its own tally is at least 67,000 people rescued in more than 21,000 emergencies, including 3,211 people in 2024 alone. ## How easily it could be taken away So how sturdy is all this? In number, very. There is not one navigation system but four with global reach: the American one, Europe’s Galileo, Russia’s GLONASS and China’s BeiDou, and a modern phone listens to several at once. Galileo’s satellites fly a little higher than GPS, at 23,222 kilometres, and the European Space Agency says more than five billion smartphone users now rely on them. In kind, it is fragile. A navigation signal has travelled 20,000 kilometres by the time it reaches you, and it arrives extraordinarily faint. It can be drowned out by a cheap transmitter, or imitated by a clever one. An industry group that tracks this found that by August 2024 an average of 1,500 flights a day were being fed false positions, five times the rate at the start of that year. In October 2025 the assembly of the United Nations aviation agency formally condemned interference it traced to North Korea and Russia. Pilots have other instruments. A delivery app does not. The Sun can do it too. During the great solar storm of 10 to 12 May 2024, in the middle of the planting season, precision guidance failed on farms across the American Midwest. One agricultural economist put the cost to growers at more than half a billion dollars. > One wrong number in January 2016 was thirteen millionths of a second, and it set off alarms around the world. Governments have begun to act as though they believe their own estimates. In November 2025 Britain announced 155 million pounds for backups, including a ground-based radio navigation system and a national timing centre that does not depend on the sky. ![The sky before sunrise from Leeds with constellation lines above a dark horizon, beside a list of the satellites passing over this morning](/media/what-do-satellites-do/morning-sky-en.jpg) *The sky over Leeds before sunrise, with the satellites that cross it in that hour. Most of the machines in this story are too high or too faint to see; these are the few that are not.* Tomorrow morning, then, before breakfast. When the phone lights up, give it one extra second of attention. The time on it came down from a clock that Einstein had to correct. The cloud icon came from a camera hanging over the Gulf of Guinea. And if you step outside and find a satellite dish on a neighbour’s wall, look along it: it is pointing at one particular machine, some 36,000 kilometres above the equator, and it has never once needed to move. > **About Space Radar.** Space Radar is a free, open-source live 3D map of everything in orbit: satellites, stations, debris, rockets, planets and stars, each at its real, computed position. It runs in the browser with no account at [spaceradar.ai](https://www.spaceradar.ai/). **Fly there in the 3D map:** [The living Earth, seen from its satellites](https://www.spaceradar.ai/#trip=the-living-earth). Free, in your browser, no account. ## Questions people ask ### What do satellites do? They tell the time, fix positions, relay calls, television and internet, photograph weather, land and sea, and listen for distress beacons. Most of what an ordinary person uses them for happens without their knowing: phone networks, payments, forecasts and maps all depend on them. ### How does GPS work? Each GPS satellite broadcasts the exact time and its own position. A receiver measures how long the signals from at least four satellites took to arrive, turns those delays into distances, and solves for where it is and what time it is. ### How many GPS satellites are there? About thirty-one are in operation, flying at roughly 20,200 kilometres in six orbital planes. Europe’s Galileo, Russia’s GLONASS and China’s BeiDou run similar constellations, and most phones use several of them together. ### What would happen if GPS stopped working? Navigation would be the visible loss, but timing would be the serious one: mobile networks, power grids and financial markets use GPS time to stay in step. Estimates of the cost run to about a billion dollars a day for the United States alone. ## Sources 1. [All rely on precision timing](https://archive.gps.gov/applications/timing/) 2. [About a billion dollars a day](https://www.nist.gov/news-events/news/2019/10/economic-benefits-global-positioning-system-us-private-sector-study) 3. [Gpsworld.com: report what on earth is the value of space](https://www.gpsworld.com/report-what-on-earth-is-the-value-of-space/) 4. [Gps.gov: space segment](https://www.gps.gov/space-segment) 5. [Archive.gps.gov: control](https://archive.gps.gov/systems/gps/control/) 6. [Archive.gps.gov: sa](https://archive.gps.gov/systems/gps/modernization/sa/) 7. [Finra.org](https://www.finra.org/rules-guidance/rulebooks/finra-rules/6820) 8. [Insidegnss.com: gps experiences utc timing iif satellite launcher problems](https://insidegnss.com/gps-experiences-utc-timing-iif-satellite-launcher-problems/) 9. [Gov.uk: landmark government investment to safeguard the essential signals we all rely on](https://www.gov.uk/government/news/landmark-government-investment-to-safeguard-the-essential-signals-we-all-rely-on) 10. [Nesdis.noaa.gov: celebrating 60 years world's first weather satellite](https://www.nesdis.noaa.gov/content/celebrating-60-years-world's-first-weather-satellite) 11. [Nesdis.noaa.gov: noaas goes 19 now operational goes east providing critical new data forecasters](https://www.nesdis.noaa.gov/news/noaas-goes-19-now-operational-goes-east-providing-critical-new-data-forecasters) 12. [Wmo.int](https://wmo.int/node/24968) 13. [Ecmwf.int](https://www.ecmwf.int/node/38367) 14. [Usgs.gov: landsat 9](https://www.usgs.gov/landsat-missions/landsat-9) 15. [Ers.usda.gov: most row crop acreage managed using auto steer and guidance systems](https://ers.usda.gov/amber-waves/2023/april/most-row-crop-acreage-managed-using-auto-steer-and-guidance-systems) 16. [Imo.org: AIS.aspx](https://www.imo.org/en/OurWork/Safety/Pages/AIS.aspx) 17. [Icao.int: AI03%20WP04%20Status%20of%20the%20Cospas Sarsat%20Programme.pdf](https://www.icao.int/sites/default/files/APAC/Meetings/2026/2026%20APSARWG11/03-Working%20Papers/AI03%20WP04%20Status%20of%20the%20Cospas-Sarsat%20Programme.pdf) 18. [Esa.int: Two new Galileo satellites enter service](https://www.esa.int/Applications/Satellite_navigation/Two_new_Galileo_satellites_enter_service) 19. [Ops.group: gps spoofing final report](https://ops.group/blog/gps-spoofing-final-report/) 20. [Icao.int: icao assembly condemns gnss radio frequency interference originating dprk and russian](https://icao.int/news/icao-assembly-condemns-gnss-radio-frequency-interference-originating-dprk-and-russian) 21. [Extension.k-state.edu: agriculture solar weather gps outage](https://extension.k-state.edu/news-and-publications/news/stories/2025/04/agriculture-solar-weather-gps-outage.html) --- # Solar Eclipse 2027: Six Minutes of Night at Noon > The solar eclipse of 2027 will put Luxor in the dark for more than six minutes, the longest totality anyone will stand under until 2114. Here is the day, minute by minute, and where the shadow does and does not reach. By Ivan Akselrot. Published 2026-09-27. Category: Skywatching. Tags: solar eclipse, eclipse 2027, Moon, totality, Luxor. 11 min read. Canonical: https://blog.spaceradar.ai/solar-eclipse-2027-six-minutes/ At about two minutes past one in the afternoon on Monday 2 August 2027, on the east bank of the Nile at Luxor, noon will stop. The Sun will be almost straight overhead, 82 degrees up, in a sky that has very likely not held a cloud for weeks. For an hour and twenty minutes the Moon will have been sliding across it, and for the last few of those minutes the light on the temple columns will have gone thin and silvery, like daylight seen through dark glass. Then the last bead of sunlight will go out. A shadow 258 kilometres wide, which crossed the Strait of Gibraltar an hour and a quarter earlier, will arrive over the Valley of the Kings from the north-west. Where the Sun was there will be a black disc with a pale crown of light around it. Venus will appear right beside it. It will stay that way for about six minutes and twenty seconds. This is the solar eclipse of 2027, and it is not an ordinary one. Its longest totality, 6 minutes 23 seconds, falls about 60 kilometres south-east of Luxor, and nobody on Earth will stand under a longer one until 2114. I have been running that Monday forwards and backwards in [Space Radar](https://www.spaceradar.ai/), a free live map that draws the Moon’s shadow where the Sun and Moon really are. This is what will happen, who will see it, and why people who have seen one total eclipse cross the planet to see another. ## Cádiz to Luxor in seventy-eight minutes The shadow first touches the Earth at sunrise in the Atlantic. It makes land at the Strait of Gibraltar, in the middle of a Spanish summer morning. According to [Spain’s National Astronomical Observatory](https://astronomia.ign.es/eclipses-de-sol-y-luna/eclipse-total-sol-de-2-de-agosto-2027), Cádiz goes dark at 10:45 local time for 2 minutes 54 seconds, Málaga three minutes later for 1 minute 48, and Ceuta, on the African side, for 4 minutes 48. Tarifa, the southern tip of Europe, gets more than four and a half minutes. From there the path runs east along the coast of North Africa and grows longer as it goes, because the Sun climbs higher: nearly five minutes at Tangier, about five at Oran, five and three-quarters at Sfax in Tunisia, just over six at Benghazi. It crosses the Libyan desert and the Nile, leaves Africa at the Red Sea, gives Jeddah six minutes and Mecca about five, and thins out again across Yemen and the tip of Somalia before it lifts off the planet at sunset in the Indian Ocean. ![The Earth from the Sun’s side with the Moon’s shadow over the Red Sea and western Arabia](/media/solar-eclipse-2027-six-minutes/05-08-shadow-red-sea.jpg) *10:25 Universal Time: the shadow has crossed the Red Sea and lies over Jeddah. Twenty minutes earlier it was at Luxor.* - **78 minutes** The shadow’s run from Cádiz to Luxor, 3,900 km apart: about 3,000 km/h on average, faster than any airliner now flying. You can watch the whole crossing in a couple of minutes: [follow the Moon’s shadow across the Earth](https://www.spaceradar.ai/#trip=chasing-the-solar-eclipse) from the hour before it arrives, or open the map at the minute [the shadow reaches the Strait of Gibraltar](https://www.spaceradar.ai/#t=2027-08-02T08:47:30Z&cam=184.2,58.4,19110). **Fly there in the 3D map:** [Follow the Moon’s shadow across the Earth](https://www.spaceradar.ai/#trip=chasing-the-solar-eclipse) ![Europe and North Africa from space with the Moon’s shadow lying over southern Spain and Morocco, city lights showing inside the darkened area](/media/solar-eclipse-2027-six-minutes/05-03-shadow-over-gibraltar.jpg) *08:47 Universal Time: the dark core is over the Strait of Gibraltar, and the lights of Spain and Morocco show through the shadow. Southern Spain has totality in mid-morning, with the Sun 38 degrees above the eastern horizon.* ## What Madrid, Tel Aviv and Moscow will see Outside that narrow track the same eclipse is partial, and a very large part of the world gets a share of it. These figures are the fraction of the Sun’s disc that is covered at the deepest moment, computed for each city. Spain outside the path comes close: Seville 98 per cent, Lisbon 92, Madrid 86, Barcelona 82. Further north the bite shrinks: Rome 74 per cent, Athens 78, Paris 51, London 42, Berlin 34. Israel lies north of the path and sees a deep partial eclipse in the early afternoon. Tel Aviv and Jerusalem have about 80 per cent of the Sun covered at 13:00, Haifa 77, Eilat 89. Cairo gets 95 per cent, and so does Sharm el-Sheikh. The Red Sea resort of Hurghada, at about 98, misses totality by a short drive. Russia sees only the outer edge. In Moscow the Moon covers 9 per cent of the Sun around 12:40, in St Petersburg 6. The south does better, with roughly a third of the Sun covered in Sochi and Krasnodar. Beyond the Urals, in Yekaterinburg or Novosibirsk, there is no eclipse at all. ![Close view of north-east Africa and Arabia at greatest eclipse: the dark core of the shadow lies across the Nile and the Red Sea coast, with a grey fringe reaching Cairo, Sinai and Israel](/media/solar-eclipse-2027-six-minutes/05-13-shadow-greatest-close.jpg) *Greatest eclipse, seen closer. The string of lights is the Nile. Cairo, Sinai and Israel sit in the grey outer shadow: a deep partial eclipse, seen only with eye protection, and no night.* ## Why 99 per cent is nothing like 100 It is tempting to think that 95 per cent of an eclipse is 95 per cent of the experience. It is closer to none of it. The Sun’s outer atmosphere, the corona, is always there. It is also about a million times fainter than the Sun’s surface, roughly as bright as a full Moon. So while even one per cent of the surface is showing, that sliver is still ten thousand times brighter than the corona, and the sky stays blue. In Cairo on 2 August the light will turn strange and the shadows sharp, and people who look through eclipse glasses will see a thin crescent. But the day will not end. > It is tempting to think that 95 per cent of an eclipse is 95 per cent of the experience. It is closer to none of it. Inside the path the last per cent goes in a few seconds, and everything changes at once. The corona appears. The brightest planets come out: Venus less than three degrees from the Sun, Mercury to one side and Jupiter to the other. At Luxor, so will the stars that belong to winter evenings. Sirius and Orion are in the August sky every day, hidden by daylight, and for six minutes they will be there in the south-west. All round the horizon, 130 kilometres away in every direction, there will be the orange glow of places where the Sun is still shining. ![The daytime sky over Luxor at the minute of totality as Space Radar draws it: the Sun high overhead with the constellations Cancer, Gemini, Orion and Canis Major labelled around it](/media/solar-eclipse-2027-six-minutes/05-05-sky-luxor-totality.jpg) *Luxor at 13:05 local time on 2 August 2027, looking up. The map draws ordinary daylight and labels what is hidden behind it. For six minutes the eclipse will switch the blue off.* It is this, and not the darkness, that people travel for. You can see where the Moon is standing to do it, too: [look back from the Moon at its own shadow on the Earth](https://www.spaceradar.ai/#trip=chasing-the-solar-eclipse&stop=3). **Fly there in the 3D map:** [Look back from the Moon at its own shadow on the Earth](https://www.spaceradar.ai/#trip=chasing-the-solar-eclipse&stop=3) ![The sunlit far side of the Moon in the foreground and beyond it a small Earth with a dark spot on it](/media/solar-eclipse-2027-six-minutes/05-04-from-the-moon.jpg) *The view from 12,000 km behind the Moon. The side facing the camera is in full sunlight, which is why the side facing the Earth is dark: a solar eclipse can only happen at new Moon.* ## The people who run after shadows They call themselves umbraphiles, shadow lovers, and the most committed of them did something on 30 June 1973 that has never been repeated. Seven scientists boarded the prototype Concorde, flew at twice the speed of sound along the path of an eclipse over the Sahara, and kept up with the shadow. They had [74 minutes of totality](https://en.wikipedia.org/wiki/1973_Concorde_eclipse_flight) in a single sitting. It is still the record. The rest of us stand still and let the shadow come to us, and for Spain it is coming often. The eclipse of 2027 is the second of three in three summers: a total eclipse crossed the north of the country on 12 August 2026, and a ring-shaped one follows in January 2028. Science has run after shadows as well. On 18 August 1868, during an eclipse in India, the French astronomer Pierre Janssen pointed a spectroscope at the edge of the Sun and saw a yellow line that matched no known element. It was named helium, after the Sun, and was not found on Earth for another 27 years. On 29 May 1919 Arthur Eddington photographed the stars around an eclipsed Sun from the island of Príncipe and found them slightly out of place: the Sun’s gravity had bent their light, by the amount Einstein had predicted four years earlier. And the oldest story of all is Herodotus’s. In 585 BC, he wrote, the Lydians and the Medes were in the middle of a battle when day turned to night, and they put down their weapons and made peace. ## A coincidence with an expiry date Total eclipses exist because of a fluke. The Sun is about 400 times wider than the Moon and about 400 times farther away, so from the ground the two discs are almost exactly the same size. No other planet in the Solar System has such a match. The fit is not perfect, and that is why this eclipse is long. On 2 August 2027 the Moon reaches its nearest point to the Earth for the month less than four hours before greatest eclipse, so it looks large. The Earth, a month after its farthest point from the Sun, sees a Sun that looks small. And the shadow falls near the tropics at midday, where the ground is nearest the Moon. The theoretical limit is about seven and a half minutes; 6 minutes 23 seconds is as near to it as this century’s remaining eclipses get. When the fit goes the other way, with the Moon far and small, a bright ring of Sun is left over and the day never ends. The map shows that kind too, [in the same trip](https://www.spaceradar.ai/#trip=chasing-the-solar-eclipse&stop=4). **Fly there in the 3D map:** [In the same trip](https://www.spaceradar.ai/#trip=chasing-the-solar-eclipse&stop=4) ![The Earth with a fainter, smaller shadow on it during an annular eclipse](/media/solar-eclipse-2027-six-minutes/05-09-ring-eclipse.jpg) *The next ring-shaped eclipse, on 6 February 2027. With the Moon too far away to cover the Sun, the shadow on the ground never becomes fully dark.* ![The full Moon turned a deep copper red during a total lunar eclipse](/media/solar-eclipse-2027-six-minutes/05-10-lunar-eclipse.jpg) *The other kind of eclipse, for those who cannot travel. On 31 December 2028 the Moon passes through the Earth’s shadow, and the whole night side of the planet can watch with nothing but its eyes.* It will not last. The Moon is moving away from us by about 3.8 centimetres a year, measured by bouncing lasers off reflectors the Apollo crews left behind. In something like 600 million years it will be too small in the sky to cover the Sun, and there will be no more total eclipses, here or anywhere we know of. ## Where to stand, and how to look Three rules do most of the planning. First, be inside the path. A hundred kilometres outside it is a different event. Within it, the nearer the centre line, the longer the totality. Second, choose your weather. Jay Anderson, the meteorologist eclipse chasers rely on, [told *Sky & Telescope*](https://skyandtelescope.org/astronomy-news/plan-for-the-2027-eclipse-of-the-century-one-year-from-now/) that just about anywhere in Tunisia, Libya and Egypt offers a good to excellent chance of clear sky. Egypt and Libya also regularly pass 40 °C in August. Southern Spain is gentler and far easier to reach, at the cost of a shorter totality and some risk of Saharan dust or coastal fog. Third, protect your eyes, and know the one exception. For every partial stage, anywhere, you need eclipse glasses or a viewer that meets the ISO 12312-2 standard; [NASA is blunt](https://science.nasa.gov/eclipses/safety/) that ordinary sunglasses, however dark, are not safe. Never look through binoculars or a camera with only eclipse glasses on. During totality itself, and only then, you take the glasses off and look. The moment the first bead of Sun returns, they go back on. > Six minutes is long for an eclipse and short for anything else. And if it is your first, do not spend it behind a camera. Six minutes is long for an eclipse and short for anything else. Until then you can [open your own sky at the minute of greatest eclipse](https://www.spaceradar.ai/#m=now&t=2027-08-02T10:06:34Z) and see where the Sun will be standing; the map guesses your place from your time zone, so set your town first. On the map the shadow is a small soft-edged spot crossing North Africa. On the ground it will be the largest thing most of the people under it have ever seen move, and it will arrive on time to the second. *Times and coverage for cities outside Spain were computed with the open-source Astronomy Engine library and checked against NASA’s and Spain’s published figures; they are good to a few seconds and about one per cent. Space Radar is a free, open-source live 3D map of everything in orbit, with the Sun, Moon and their shadows drawn where they really are. It runs in a browser at [spaceradar.ai](https://www.spaceradar.ai/), with no account.* **Fly there in the 3D map:** [Follow the Moon’s shadow across the Earth](https://www.spaceradar.ai/#trip=chasing-the-solar-eclipse). Free, in your browser, no account. ## Questions people ask ### When and where is the total solar eclipse of 2027? On Monday 2 August 2027. Totality is visible along a track through southern Spain, Morocco, Algeria, Tunisia, Libya, Egypt, Saudi Arabia, Yemen and Somalia; most of Europe, Africa and western Asia see a partial eclipse. ### How long will the 2027 eclipse last? Up to 6 minutes 23 seconds of totality near Luxor in Egypt, and from about two to five minutes in southern Spain and Morocco. The partial stages last well over two hours. ### Is it the longest eclipse of the century? It is the second longest; the eclipse of 22 July 2009 reached 6 minutes 39 seconds, mostly over the Pacific. No total eclipse will be longer than 2027’s until 3 June 2114. ### Is it safe to look at a solar eclipse? Only through eclipse glasses or viewers that meet ISO 12312-2, except during the few minutes of totality, when the Sun is completely covered and can be seen directly. ## Sources 1. [Told *Sky & Telescope*](https://skyandtelescope.org/astronomy-news/plan-for-the-2027-eclipse-of-the-century-one-year-from-now/) 2. [Spain’s National Astronomical Observatory](https://astronomia.ign.es/eclipses-de-sol-y-luna/eclipse-total-sol-de-2-de-agosto-2027) 3. [74 minutes of totality](https://en.wikipedia.org/wiki/1973_Concorde_eclipse_flight) 4. [NASA is blunt](https://science.nasa.gov/eclipses/safety/) 5. [Eclipse.gsfc.nasa.gov: SEdata](https://eclipse.gsfc.nasa.gov/SEsearch/SEdata.php?Ecl=20270802) 6. [Eclipsewise.com: SE2027Aug02Tprime](https://eclipsewise.com/solar/SEprime/2001-2100/SE2027Aug02Tprime.html) 7. [Eclipse.gsfc.nasa.gov: SE2001 2100](https://eclipse.gsfc.nasa.gov/SEcat5/SE2001-2100.html) 8. [Aa.usno.navy.mil: Earth Seasons](https://aa.usno.navy.mil/data/Earth_Seasons) 9. [Eclipse262728.es](https://eclipse262728.es/) 10. [St.llnl.gov: airborne pursuit total eclipse](https://st.llnl.gov/news/look-back/airborne-pursuit-total-eclipse) 11. [Space.com: on this day in space aug 18 1868 total solar eclipse leads to discovery of helium](https://www.space.com/astronomy/on-this-day-in-space-aug-18-1868-total-solar-eclipse-leads-to-discovery-of-helium) 12. [Science.nasa.gov: history](https://science.nasa.gov/eclipses/history/) 13. [Revistapesquisa.fapesp.br: when light bent](https://revistapesquisa.fapesp.br/en/when-light-bent/) 14. [Bendbulletin.com: how long we will see total solar eclipses before the moon ditches us](https://bendbulletin.com/2024/01/07/how-long-we-will-see-total-solar-eclipses-before-the-moon-ditches-us) 15. [Stardate.org: rare eclipse](https://stardate.org/astro-guide/featured-images/rare-eclipse) 16. [Spaceradar.ai](https://www.spaceradar.ai)