Radar signal processing for space debris observation

The steadily growing number of space debris objects poses a severe hazard to all kinds of space operations. Especially the population of objects in the mid-size (1 to 10 cm) regime is currently not well known due to the limited sensitivity of sensors used for observation of space objects in Low Earth Orbit (LEO). Therefore, space agencies are developing models to describe the debris population in a statistical way. These have to be supported and verified by measurements. Large ground-based radars like FGAN's Tracking and Imaging Radar (TIRA) are well suited to assess the mid-size debris population due to its outstanding sensitivity and its all-weather and day-and-night performance. A Beam-Park observation mode and special signal and detection processing techniques have been developed. The radar antenna is "parked" for 24 In in a fixed direction. The rotation of Earth moves the beam through a complete revolution (360degrees) of right ascensions of the ascending node. The echoes of all objects passing the beam within a given range window are continuously recorded during this time. Detection processing and target parameter estimation is carried out offline by software means. In contrast to a pure hardware-based signal processing scheme this gives a high degree of flexibility allowing even re-processing the data with different algorithms. In this paper signal and data processing techniques for the detection and parameter assessment of small targets at long ranges during Beam-Park Experiments (BPE) with the L-band radar of the TIRA system are explained. It is shown that the chosen software-based concept is able to cope with the vast amount of raw data collected during such 24 hour campaigns with reasonable processing times. The performance of these techniques is demonstrated by sample results of recent BPE campaigns.