The Astronomical Institute of the University of Bern (AIUB) performs optical surveys for sub-catalogue space debris in high-altitude orbits since more than two decades. The bulk of the data is acquired on behalf of ESA with the ESA 1-meter telescope at the Optical Ground Station (OGS) in Tenerife, Spain. Additional surveys are performed with the 0.8-meter Zimmerwald Multiple Applications Telescope ZimMAIN at AIUB’s Zimmerwald Observatory in Switzerland. Continuous observation campaigns are key to monitor this environment for new sources of space debris. Results from the last 5 years indicate the appearance of several new clusters of fragments and emphasize the dynamical nature of this environment. Preliminary findings of a larger effort to consistently re-process the data of 22 years of surveys, analyse possible observational selection effects, and to compare the actual observations with reference populations, in particular the MASTER population, will be presented.
