When Will the ISS Pass Over Me? How to Spot the International Space Station
Some evenings, a little after sunset, a bright, steady light rises in the west and glides silently across the sky in a few minutes, then fades away. It is not a plane and not a star. It is the International Space Station, with people on board, about 400 km overhead. It is one of the easiest and most rewarding sights in the night sky. All you need is to know when to look.
What the ISS is
The ISS is a laboratory in orbit, built and run by the space agencies of the United States, Russia, Europe, Japan and Canada. It has had people on board without a break since November 2000. For a spacecraft it is enormous: about 109 m from end to end, roughly the length of a football pitch, with a mass of about 420,000 kg. Its wide solar arrays are a big part of why it looks so bright: they catch sunlight and reflect it down to us.
- Height: about 400 km (250 miles) above the ground. It slowly sinks in the thin upper air and is boosted back up from time to time.
- Speed: about 28,000 km/h (17,500 mph), nearly 8 km every second.
- One orbit: roughly 90 minutes, about 16 orbits a day. The crew sees about 16 sunrises and 16 sunsets every 24 hours.
Why you only see it around dawn and dusk
The ISS carries no lights bright enough to see from the ground. What you see is sunlight bouncing off it, just as with the Moon. So two things have to be true at once: your sky has to be dark, and the station has to be in sunshine.
That happens in the hours after sunset and before sunrise. The Sun has set for you on the ground, but 400 km up the station can still see it, the way a high mountain peak stays lit after the valley below has fallen into shadow. A station right overhead stays sunlit until the Sun is roughly 20° below your horizon. Later in the night the station flies through Earth's shadow and is invisible, even if it passes straight over you.
At midday it is in sunshine, but the sky is far too bright: as NASA puts it, unlike the Moon, the station is not bright enough to see in daylight. Around midsummer at mid and high latitudes, on the other hand, the station can stay sunlit all night, and you may catch several passes in one night, each about 90 minutes after the last.
You will also notice that passes come in runs: a few days with evening passes, then none for a while, then a run of morning passes. Depending on where you live, NASA says, viewing chances range from about one a month to several a week.
How bright it looks and how long a pass lasts
On a good pass the ISS is brighter than any star, and on a high pass it can rival the brightest planets. Its brightness changes as it crosses. Low over the horizon it is about 1,500 km away from you; near the top of a pass that goes overhead it is only about 400 km away, more than three times closer, and much brighter. Passes that stay low are far less impressive than high ones.
A pass is short. Even directly beneath its path, the station takes only about six minutes to travel from 10° above one horizon to 10° above the other, and most passes are lower and shorter than that. Often it does not set at all: it fades out partway across the sky, over a few seconds, as it slips into Earth's shadow. On some morning passes the reverse happens, and it switches on out of nowhere as it comes out of the shadow.
How to predict a pass over you
The orbits of the ISS and thousands of other satellites are tracked and published as sets of numbers called orbital elements. From those numbers and your location, a computer can work out when the station will be visible from where you stand. You do not need to do the maths yourself:
- Now & Here lists the next visible passes of the ISS and China's Tiangong over you in the next three days: the start time, the compass direction where the station appears and where it disappears, the highest point it reaches in degrees and how many minutes it is up. It only lists passes you can actually see with your eyes, with the station at least 10° up and lit by the Sun while your sky is dark. The orbits come from CelesTrak's latest elements.
- NASA's Spot the Station sends alerts for upcoming ISS passes at the places you choose.
Now & Here estimates your location from your network; for the best timing you can let it use your device's exact position, which stays on your device. Times are shown in your device's time zone.
Reading a pass is easy. "W → NE, up to 60°, 5 min" means: at the start time, look west; the station climbs to 60° above the horizon (two thirds of the way up, as straight overhead is 90°) and disappears towards the northeast about five minutes later. A fist held at arm's length covers about 10° of sky, which helps you judge heights.
Watching a pass
- Be outside a few minutes early, facing the direction where it will appear, and let your eyes adjust.
- You need no telescope or binoculars: NASA notes that the bare eye is all it takes.
- The station always travels broadly from west to east, because, like most satellites, it orbits in the same direction as Earth turns.
- For a photo, rest a camera or phone on something steady and take an exposure of several seconds: the station draws a bright streak across the stars.
ISS, plane or Starlink?
- A plane has blinking lights, usually red and green with white strobes, and you can often hear it. It may turn. The ISS shines with one steady white or slightly yellowish light, makes no sound and follows a smooth arc. NASA also notes that it moves faster than a typical airplane.
- Other satellites look like the ISS but are much fainter; many are only visible from a dark site.
- A Starlink train is a line of dozens of points of light, one behind the other, moving together. SpaceX launches its internet satellites in batches, and for the first days they fly low and close together before spreading out and climbing to their working orbits. Measurements by Mallama and colleagues found the newer Starlink satellites averaging about magnitude 2.7 while still low, easy to see, but only about 6.5, at the very limit of the naked eye, once SpaceX starts dimming them at about 357 km up.
- Tiangong, China's space station, also makes visible passes. It is smaller than the ISS, so it looks fainter, and its orbit is tilted 41.5° to the equator, so from high latitudes it stays low or never appears.
See where it is right now
Missed a pass? Earth's orbit, live shows where the ISS, Tiangong, Hubble, the Starlink satellites and every other tracked satellite are at this moment, around a 3D Earth, from public orbit data refreshed every few hours. Tap the station to see its height, its speed, how long one orbit takes and what it is flying over right now. Then open Now & Here to find out when it will next pass over you.
Frequently asked questions
Can you see the ISS with the naked eye? Yes. On a good pass it is brighter than any star and needs no telescope or binoculars. It looks like a bright, steady star moving smoothly across the sky in a few minutes.
Why can't I see the ISS in the middle of the night? Because it shines by reflected sunlight. Late at night the station is usually in Earth's shadow, so it is dark even when it passes overhead. It is visible in the hours after sunset and before sunrise, when it is still sunlit and your sky is dark.
How long is the ISS visible during a pass? From a minute or two for a low pass to about six minutes for one that goes nearly overhead. It often fades out before reaching the horizon as it enters Earth's shadow.
How fast does the ISS move? About 28,000 km/h, nearly 8 km every second. It goes round Earth in roughly 90 minutes, about 16 times a day.
Explore it yourself: Earth's orbit, live · Now & Here · Sky calendar · What can I see in the night sky tonight?
Sources
- NASA, International Space Station Facts and Figures: size, mass, 16 orbits a day, crewed since November 2000. nasa.gov
- NASA, Spot the Station: speed, when sightings happen and how to recognise the station. nasa.gov
- NASA, Spot the Station: Frequently Asked Questions: daylight visibility, how often sightings occur. nasa.gov
- CelesTrak (T. S. Kelso): orbital elements from US Space Force tracking. celestrak.org
- Mallama et al. (2024), The Brightness of Starlink Mini Satellites During Orbit-Raising. arXiv:2405.12007
Derived for a station 420 km up and Earth's radius of 6,371 km, ignoring the atmosphere: orbital speed √(GM/r) ≈ 7.66 km/s (about 27,600 km/h) and one orbit 2πr/v ≈ 93 minutes; directly overhead, the station stays sunlit until the Sun is arccos(6,371/6,791) ≈ 20° below the horizon; seen 10° above the horizon it is about 1,490 km away; between 10° above opposite horizons an overhead pass covers 25° of its orbit, about 6.5 minutes (Earth's rotation changes this slightly).