Stellar navigation

Scientists at DTU Space have developed a stellar compass, which today is an indispensable instrument aboard numerous European and US space probes and satellites.

A stellar compass enables satellites and space probes to orient themselves so scientists always know precisely which way the satellite is facing in space. Without this information, scientific measurements from satellites are often useless.

The stellar compass comprises two main parts: a digital camera that photographs the night sky and a computer that matches the digital images against a stellar map stored in the computer. By comparing images of the night sky with the stellar map, the stellar compass is able to determine what direction it or the space probe is facing.  



Facts about the stellar camera

The stellar compass is able to determine its direction in space with an uncertainty of as little as 1.5 arc seconds. This corresponds to us being able to see the top and bottom edge of a flat penny at a distance of 300 metres. 

The stellar compass was originally developed for the Danish Ørsted satellite. It was tested for the first time in 1995 aboard a NASA probe called Thunderstorm, which tested new technologies for use in space. Since then, DTU Space has further developed the stellar compass so it has become increasingly compact and sophisticated, and to date the instrument has flown on more than 30 international missions, including Astrid II, TeamSat, CHAMP, PROBA and GRACE, with the prospect of many more to come.