The International Space Station orbits the Earth many times per day. And if you want to view it and pretend it's Santa's sleigh nipping around delivering presents, you should be able to watch it this Christmas Eve.
It's a great thing to do with your kids, and interested family members. And we'll explain how to track the ISS so you don't miss it - it's only visible for a few minutes at a time.
Last year, the ISS was only visible during the morning of Christmas Eve (24 December) around 7.30am. The times haven't yet been published for 2019, but we'll update this article when have the information from NASA.
During the day, it's much harder to spot the ISS, but at night it's the third brightest object in the sky, and looks like a plane, although flying much higher and faster.
It's wise not to promise your kids too much just in case you don't quite catch a glimpse of it - and you won't if it's cloudy - but we recommend using the apps below to find a time when it will be dark and overhead to show them the Space Station and explain what it really is, because the ISS is super cool too. (Find out more about the Space Station by reading on).
To get the ultimate experience, you'll want to use an ISS tracker, which is an app you install on your phone. We've found the following apps to be the most accurate and useful.
The GoISSWatch app for iOS is the best app to track the International Space Station with on iPhone. 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.
It isn't available for Android.
An alternative app - for iOS again - that works almost as well is the ISS Finder app, although its bright white design 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.
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 pass, 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 gauge 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).
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 16 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.