There are satellites in orbit that are part of the GPS network, a system where we can locate a specially modified computer to anywhere on Earth to within 5 metres. Santa has one of these computers, which is known as a transceiver.

Normal people can use these satellites too, for example with in-car navigation. But you won't be able to see them, as they look like normal stars in the night sky.

The Lovell Radio Telescope in Cheshire, UK is one of the dishes being used on Christmas Eve. Information is received here, then sent back to a central location where the Royal Air Force can monitor his progress and make sure Santa receives a trouble free flight.

With more and more aeroplanes in the sky, it is very important that they do not go too near otherwise Christmas may be cut short!