Passive optical space surveillance system for initial LEO object detection

Abstract

In order to avoid collisions of active satellites with space debris, the low earth orbit (LEO) object population must be continuously scanned and the orbits of all objects must be updated regularly. Passive and active optical observation methods can deliver high accuracy time resolved position measurements of LEO objects allowing accurate orbit determination. Space debris laser ranging stations need accurate a priori orbit information on the position of the object in order to observe it. The Institute of Technical Physics at the German Aerospace Center in Stuttgart operates an observatory to perform passive as well as active optical measurements to LEO objects. To detect unknown objects a wide-angle imaging system with 15° field of view equipped with an astronomical CCD camera was designed and set up to continuously observe the sky for LEO objects. The system is capable of detecting 25 objects per hour on observation campaigns during twilight at the observatory in city center. The angular coordinates of detected objects are measured roughly without any a priori information. This paper evaluates the properties of such a “stare” system experimentally. Additionally simulations are performed with ESA PROOF software to validate the measurements and obtain system performance. The simulation show that objects as small as 50 cm can be detected by the system and 60% of all objects larger than 1 m are detected.