Mikrowellenmessverfahren zur erdgebundenen hochgenauen Abbildung von Weltraumobjekten auf erdnahen Umlaufbahnen (IoSiS-Imaging of Satellites in Space)

Abstract

In the last decade the number of operating satellites orbiting the Earth has increased as never before. It has to be expected, that the total number of satellites, and especially the rate of increase per year, both will keep growing. Considering the potential hazard of damage and destruction by space debris, which is already nowadays massively present in a low earth orbit, ISAR imaging can provide crucial information to characterize the status of satellites and other space objects. The particular work is discussing theoretical and especially experimental analysis and results of an imaging radar providing very high spatial resolution. Those results are considered as the basis for a novel high-performance radar-based imaging concept for the application of space surveillance where the novelty will be realized in rather small distributed apertures and the separation of transmitters and receivers compared to existing space surveillance radars. The theoretical analysis considers the whole system, i.e. radar electronics, wave propagation, space dynamics of orbiting objects and radar image formation, including all error sources which may be present in a highresolution imaging radar for space object observation. Based on the implemented system simulator and model-based reflectivity maps of real satellites, the impact of such errors on the ISAR image quality is discussed. Using theoretical results the experimental imaging system IoSiS was designed and constructed. In commissioning experiments the performance of the developed satellite imaging radar is validated. In particular, further experiments reveal some unique and detailed high-quality radar images of the International Space Station. Finally, the work provides a detailed analysis for enhancing the system performance by using higher millimeter-wave frequencies and separated apertures. This new approach will allow highest spatial resolution and imaging concepts like radar interferometry, for instance, being not used so far for space observation.