The International Space Station (ISS) is a frequent feature in our skies. It’s usually quite bright and is easily seen with the naked eye. It travels fast though, making it easy to miss unless you know when to expect it and where to look.
In orbit since 1998, the ISS is by far our largest artificial satellite and is crewed with up to six people from various nations, studying and experimenting in the microgravity environment of low-Earth orbit. Travelling at a blistering 27,600 kilometres (17,150 miles) per hour, it can appear and then disappear for an observer on the Earth’s surface in a matter of minutes. In fact, it takes the ISS about 92 minutes to do one complete orbit of the Earth. How then can you spot the ISS, and what will it look like?
The ISS can look like a very bright, fast-moving star and can even be mistaken for an aircraft, although it has no navigation or other flashing lights. It will always seem to appear from the west and, depending on your location, will be seen to cross the sky low down near the horizon, or high overhead – or any place in between!
It can pass into the Earth’s shadow, in which case it seems to fade out, or a good pass can mean it is visible from horizon to horizon. Since it is moving so quickly, you may be lucky enough to see two or even three passes in the course of an evening or early morning. This of course depends on the path the ISS is taking, where you are on the Earth in relation to it, and even the clarity of the sky above you. The orbital track, or path, of the ISS changes regularly so you won’t see it every night, but you should get good visible passes approximately every six weeks if you stay in one location. Occasionally, you may get the chance to witness the ISS being joined by a Soyuz capsule carrying more crew to man the space station, or perhaps a re-supply vehicle. If this happens you will see two bright points of light closing in on one another, sometimes minutes apart or even very close together before they dock or separate.
In order to see the ISS, the first thing you need to know is when it will appear in the sky above you. This information is available from various websites and there are even some apps for smartphones and tablets that you can download, which will give you up to the minute information as to when the ISS will be viewable and where in the sky you should look in order to see it. You are going to need a clear night sky, or at least a minimal amount of cloud cover, if you are going to see it clearly.
You will also need to make sure that you are out and observing for a good few minutes before it is due to appear. Don’t forget to wrap up warm, even if you are only outside for a few minutes, and be patient – the ISS might not be visible at the exact time stated. It may be coming out of the shadow of the Earth, or it may need to climb above local obstructions such as mountains or even trees before it becomes visible to you. Seeing the ISS is great fun. Remember that there are people on board that tiny fast-moving point of light as it glides across the sky, so don’t forget to wave!
1. Research the timings. Refer to a suitable website or app for the specific time that the ISS will pass over your region. The sky will need to be dark for you to be able to see it, so check the times of twilight if you need to as well.
2. Check the weather. The weather and cloud cover will be critical in determining whether you get a good observation of the ISS. A little cloud is okay but, of course, clear skies are much better!
3. Plan and prepare. You’ll find that observing the ISS is much more relaxed if you are well prepared. Dress appropriately and wrap up warm – it’s surprising how cold you can get in just a few minutes.
4. Give yourself time. Go outside at least five minutes before the expected time of the ISS appearance. This will give you time to orientate yourself and will let your eyes adapt to the dark.
5. Find the right direction. You need to know which direction to face in order to see the ISS rise over the horizon. A compass will help if you are unsure of which way to look from your location.
6. Be patient. As the ISS sometimes has to climb over local landmasses, or perhaps even trees, you may need to wait a little longer than planned to see it. Don’t worry, if everything else is right, you’ll see it.
7. Enjoy and wave! If you’re seeing the ISS for the first time, or even if you have seen it 20 times, you’ll probably never get over the thrill. It’s especially exciting if you are observing it with children. Remember to wave!