The International Space Station is set to pass over the UK on Christmas Eve again this year, and it could quite easily be mistaken for Santa's sleigh by excited children awaiting the arrival of their presents. We know that it went down a real treat for some of the kids (and adults!) here in the PC Advisor offices when it passed over last Christmas. Here, we show you how to track the ISS so you and your kids don't miss it.
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If the sky is clear on Christmas Eve (so far the weather forecast is looking good), the ISS will be visible over the UK for a few minutes at around 5:20pm (the time will differ depending on your exact location but we'll explain more about that in a moment), but it's not always easy to spot straight away.
To get the ultimate experience, you'll want to use an ISS tracker, which you can download onto your smartphone. We've found the following apps to be the most accurate and useful.
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How to watch the International Space Station on Christmas Eve: GoISSWatch
While not the most attractive app available, we've found the GoISSWatch app for iOS to be completely accurate. It's intuitive and easy to use, and utilises the compass in your iPhone to help you know exactly which way to face to spot the ISS passing over head.
Plus, GoISSWatch can notify you five minutes ahead of each passing so that you don't miss it.
How to watch the International Space Station on Christmas Eve: ISS Finder
A better looking app that works just as well is the ISS Finder app, which has a more iOS 9-esque design but uses white backgrounds instead of black which isn't as ideal in the dark conditions you'll be using it in – light pollution isn't your friend when you're trying to spot things in space! Thankfully, there's a Night Mode that you can enable but we still find that a bit tricky to see as it puts a sort of dim red tinge over the screen.
We prefer the GoISSWatch app's 3D illustration that helps you determine where to look in the sky – ISS Finder's is less obvious so it'll take you a little longer to spot it.
What's good about ISS Finder, though, is that it offers star ratings to help you determine which date and time offers the best visibility of the ISS, at least when it comes to its position in the sky (there's no built-in weather forecast). There's also information about the Crew onboard the ISS, which we found very interesting to read.
How to watch the International Space Station on Christmas Eve on Android: ISS Detector Satellite Tracker
Both of the apps above are iOS-only, but we've also found a good Android ISS tracker called ISS Detector Satellite Tracker. It shows you a countdown to the next ISS passover, which we found to be quite useful, and has a 3D tracking diagram that's similar to the one used by GoISSWatch, with an elevation guage that works really well. You'll also find that it offers weather forecasts so you'll know whether it's likely to be visible or not.
You can quickly and easily turn on notifications to help make sure that you don't miss the ISS, too. It does have ads, though, which can be irritating but do mean that you get the app for free (as with the other apps listed here).
How to watch the International Space Station on Christmas Eve: Email alerts
If you'd prefer not to use a smartphone to track the ISS, Nasa has a dedicated website that lets you sign up for email alerts or text messages when the ISS is going to fly overhead, and also offers some advice about how to spot it in the sky.
NASA notes that the Space Station is the third brightest object in the sky, and it initially looks like a fast-moving plane, until you notice that it doesn't have any flashing lights. Alternatively, it can be initially mistaken for a very bright star until you spot how fast it's moving.
The ISS actually passes over the UK every day. In fact, it orbits the Earth 15 times every day, but some of those passes are during daylight and others can be tricky to see depending on the ISS's orbit pattern. If you miss the ISS on Christmas Eve, you can use the same tracking apps to watch it another day.
Excitingly, the first British ESA astronaut Tim Peake is currently on board the International Space Station after his arrival on 15 December. He is the sixth British-boarn person to visit the ISS and the seventh British-born person in space.