Attitude States of Space Debris determined from Optical Light Curve Observations

Abstract

The population of space debris increased drastically during the last years. Collisions involving massive objects may produce large number of fragments leading to significantly growth of the space debris population. An effective remediation measure in order to stabilize the population in LEO is therefore the removal of large, massive space debris. To remove these objects, not only precise orbits, but also more detailed information about their attitude states will be required. One important property of an object targeted for removal is its spin period and spin axis orientation. Non-resolving optical observations of the magnitude variations, so-called light curves, are a promising technique to determine rotation or tumbling rates and the orientations of the actual rotation axis of objects, as well as their temporal changes. Acquiring such observations as well extracting attitude states from these measurements is challenging and requires sophisticated observations and processing techniques. The paper will introduce the corresponding techniques and methods used at the Astronomical Institute of the University of Bern (AIUB). The 1-meter telescope ZIMLAT of the AIUB is used to collect light curves of LEO, MEO and GEO objects on a regular basis. Recently, Satellite Laser Ranging (SLR) observations of rotating LEO targets were acquired as well. We will present spin rates and their temporal evolution for a large set of decommissioned LEO, MEO and HEO spacecraft and upper stages, including more than 60 abandoned GLONASS satellites. These results were derived from more than 2000 light curves and several hundred SLR passes.