Beam-park experiments at FGAN

The space debris situation is highly dynamic due to a number of on-orbit break-ups per year and several debris producing events per month. This necessitates frequent observation campaigns with ground based sensors. During the last years in the framework of ESA-contracts FGAN conducted several observation campaigns on a yearly basis. Its TIRA (Tracking and Imaging RAdar) L-band monopulse radar was used to observe objects in LEO sized down to 2 cm passing the parked radar beam (Beam-park experiments; BPEs). Over 24-h periods complete rings in right ascension were covered. This paper will summarize the most recent observation campaigns, which covered a range window of 300 - 2000 km. They will be compared to demonstrate the changes in the debris environment over time, and the improvements of the processing will be discussed. Furthermore their results will be compared with the predictions by ESA's MASTER/PROOF'99. It is common to use data of BPEs for the estimation of the RCS of passing objects. This value is converted into an object size, which is the basis for the size distribution in orbital debris distribution models. For some objects detected in BPEs RCS are also listed in published catalogues. The difference between measured and catalogued values is not only due to statistical uncertainties, but seems to be biased. This paper tries to explain these differences. The comparability of catalogued RCS-data with those obtained from BPE's is discussed. The possibilities of extrapolation into size intervals not covered by the catalogue are investigated. A special look will be given into sidelobe detections, their identification and their treatment. For catalogued objects they might be identified by comparing the observed radar cross section (RCS) with a published one. Another option is based on the prediction of the angular offset of the object's path through the beam.