Object image linking of earth orbiting objects in the presence of cosmics

Abstract In survey series of unknown Earth orbiting objects, no a priori orbital elements are available. In surveys of wide field telescopes possibly many non-resolved object images are present on the single frames of the series. Reliable methods have to be found to associate the object images stemming from the same object with each other, so-called linking. The presence of cosmic ray events, so-called Cosmics, complicates reliable linking of non-resolved images. The tracklets of object images allow to extract exact positions for a first orbit determination. A two step method is used and tested on observation frames of space debris surveys of the ESA Space Debris Telescope, located on Tenerife, Spain: in the first step a cosmic filter is applied in the single observation frames. Four different filter approaches are compared and tested in performance. In the second step, the detected object images are linked on observation series based on the assumption of a linear accelerated movement of the objects over the frame during the series, which is updated with every object image, that could be successfully linked. As results it has to be stated. Firstly, the automatic discrimination of cosmics and non-resolved object images on single frames remains difficult, especially for traces with a size of only a few pixels. Secondly, on observation series, the object image linking of GEO, GTO and MEO object images is reliable for a moderate amount of object images or cosmics on the frames if at least three object images are available per object and for four object images per object even in the presence of several hundred cosmics or images on the frames with a simple approach of an updated linear accelerated movement even over long observation series.