Initial Detection and Tracking of Objects in Low Earth Orbit

For surveillance of the low Earth orbit (LEO) population the orbits of resident space objects (active satellites or space debris) has to be closely monitored. A possible solution for initial detection is the passive optical observation through wide-angle imaging systems with large fields of view (FOV). Based on measurements of these systems a short-time prediction of the object’s trajectory can be determined which is sufficiently accurate to recapture it with a high resolution telescope during the same overpass of the object. In combination with laser ranging for distance determination, the information gathered by the telescope is precise enough to generate and maintain an independent catalog. This work presents such a system consisting of a wide-field imaging system (staring) and an astronomical telescope for recapture (chasing) and precise measurements. Possible system set-ups are analyzed and evaluated based on the simulation tool PROOF (Program for Radar and Optical Forecasting) provided by the European Space Agency (ESA). These simulations result in a recommended pointing towards zenith for passive optical space surveillance, where the observation time starts 1.5 h after sunset and ends 1.5 h before sunrise. General calculations and corresponding PROOF simulations show the dependence of the aperture of the staring camera lens to the detectable object size. According to these simulations a camera system consisting of a FLI PL16308 camera and a 135 mm f/2.0 lens are a good combination with respect to the FOV (15.27 ° × 15.27 °) and detectable size of 0.45 m. Per day 3422 different objects contained in the TLE- database are passing this FOV. Furthermore the developed algorithm for initial object detection and tracking is presented. This algorithm is able to detect orbiting objects on a star background, assigns them to related detections from earlier images and predicts a future position for recapture the object with a high resolution telescope. The algorithm was tested at the DLR research observatory and the successful recapture is reported