Keeping an eye on the International Space Station

January 08, 2016

David Ashton-January 08, 2016

One night about a month ago I took our dogs out the front to do their business and inspect the boundaries of our ¼-acre estate. It was just after dark and I thought “I wonder if I can see any satellites up there?” I looked up and almost as I did so a very bright moving object appeared on the southern horizon. I watched it traverse the sky, passing almost right overhead. It was much brighter than Venus which is usually the brightest object in the post-sunset sky. It vanished over the northern horizon in a bit over 5 minutes. At best it looked a bit more than a point source, but I never thought to get my binoculars and get a better look. It had to be the International Space Station and when I got back inside I looked up the ESA’s Where is the International Space Station? page and lo and behold it had just passed almost directly overhead.

A screenshot from the ESA’s Where is the International Space Station?
webpage (source: ESA/NASA)

The ESA’s page is a great resource – it shows you a map of the world showing the trajectory of the ISS – the present position and the track for the previous 1.5 hours and next 1.5 hours. Why 1.5 hours? Well that is the time it takes for the ISS to orbit the earth, as it travels at 28800 Km/H at 400 Km above the earth’s surface. This means that the occupants get 16 sunrises and 16 sunsets every day. (I don’t think I’ll ever moan about daylight saving time again.) This is how I confirmed that it was the ISS I saw – the track passed over my part of Australia. There’s a green ellipse around it which I think shows the limits of view from earth. There is also a more detailed map that you can zoom in and out and move, which shows the precise position of the ISS above the earth in real time, changing every few seconds. In addition there is a live camera view looking down to earth, which does not seem to work very often (due to communications and other foibles) but when it does it can be quite spectacular. There’s also a wealth of other information about how it was built (the earliest bits date back to 1998) and ESA’s involvement in it.

Fossicking around a bit more I found NASA’s page on the ISS – they have a form where you can enter your location and it’ll tell you when you can see the ISS for the next week, and also their page where you can sign up for email alerts when the ISS will be visible from your location. Well, not quite. They offer lots of locations but the nearest one to me (Bathurst, NSW, Australia) is a smaller town called Lithgow, 60Km to the east of me. Why they chose Lithgow and not Bathurst or even Orange (a larger town 60 Km to the west, I don’t know, but if the ISS is visible to the west of Lithgow, then Bathurst will be able to see it as well or better. NASA thoughtfully allow you to select morning or evening appearances, or both (I selected evenings only because I am not a good morning person.) The ISS at its furthest north, passes over Canada just above the Great Lakes, and over the latitude of London. So unless you live quite far north you should be able to see it. You should get around one good viewing a month or more.

I got in my email not long ago a photo purporting to show the ISS transiting the moon, and taking up a lot of the moon’s image. This must have been photoshopped, because genuine images like the one below show how small the ISS is when transiting the moon. The ISS takes about 3 seconds to transit the moon’s face. You can get software which predicts transits of the moon’s and the sun’s face.

The ISS transiting the moon (at upper right). (Source: ESA/NASA)

The ISS has become a lot better known of late due mainly to Canadian astronaut Chris Hadfield’s viral video of “Space Oddity”. Chris Hadfield did a lot of other videos on such mundane subjects as how to brush your teeth in space, many of which were prompted by questions posed by school kids, and kudos to Chris for doing his bit for STEM education. His TED talk is also worth a look. Many people say “Oh, he’s lucky, going to space” but his TED talk makes you realize what single‑minded, focused people astronauts are. That’s what got him there, not luck.

NASA emailed me one morning recently alerting me to the fact that the ISS would be visible from Lithgow at an angle of 68 degrees at 9.20 that evening, so it should appear even higher over Bathurst. And indeed it did, it came almost overhead again, but I must say it was not as spectacular as the first time I saw it. Still very bright, but it remained a point source, even through my shoddy binoculars. Possibly this is because it was later and the sky was completely dark (though I’d have thought this would make it look brighter?)

Nevertheless it is inspiring to think that there are people living and working up there, and that there are plenty of embedded systems up there keeping it going – have any readers been concerned with those? I always bemoan the fact that we’ve not done much since the Apollo landings but this is evidence that since then, things have happened up in space. If you have not yet seen the ISS, I’d urge you to use the above resources and have a look sometime. It’s not that awe-inspiring a sight, but just knowing it is up there, in these times of global problems of one sort or another, restores your faith that mankind is not completely useless.


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