THE world's population is growing -- it was more than seven billion people at last count -- so Santa has to leave presents for more and more children each year.
It's a tough job, but Santa loves doing it and modern space technology, such as global positioning systems (GPS), help him to travel faster and more precisely.
The same satellite technology can also be used to track Santa's journey and we can all keep in touch with him on Christmas Eve.
It is thanks to NASA, the US space agency, and NORAD, a joint US and Canadian organisation that tracks airplanes, missiles and space launches around the North American continent.
NORAD and its predecessor have been doing it for more than 50 years, but as technology becomes more sophisticated, they can get a better fix on Santa's progress.
They use radar, satellites, Santa Cams, Google maps and jet fighter aircraft to keep an eye on Santa's movements.
The satellites have infra-red sensors - which means they can see heat - and can pick up Rudolph's red nose, while satellite data can show if there is any fog in Santa's path, and Rudolph can find a way through.
NORAD only uses the Santa-cams on December 24 and they are switched on about an hour before Santa enters a country. They take both video and still images of his visit.
Although Santa flies faster than any jet fighter, when he is over US airspace, they also help to keep any eye on his whereabouts. According to one pilot, Santa always waves as he passes.
To track Santa using NORAD, visit: http://www.noradsanta.org.