Optical imaging of faint geosynchronous debris with the Isaac Newton Telescope

摘要

In the six decades following the launch of Sputnik 1, thousands of satellites have been placed in orbit around the Earth. It has become increasingly apparent that this number is now dwarfed by a population of artificial debris originating from launch hardware, break-ups and long-term deterioration. Recent anomalies exhibited by the geostationary satellites Intelsat 29e, AMC-9 and Telkom 1 have highlighted the existence of a relatively uncharacterized population of faint debris at geosynchronous (GEO) altitudes, where there are no natural removal mechanisms. Previous attempts to catalogue these objects have employed the use of 1 m class optical telescopes, but regular monitoring is challenging, thus our knowledge remains sparse. We conducted a blind survey of faint geosynchronous debris using eight nights of dark/grey time on the 2.54 m Isaac Newton Telescope in La Palma, Canary Islands. A total of 129 objects with on-sky angular rates consistent with GEO were detected. We probe down to V = 21, corresponding to objects ~ 10 cm assuming an albedo of 0.1. We compare our sampled population to those of earlier surveys. The faint end of our brightness distribution continues to grow until the sensitivity limit is reached, suggesting that the modal brightness could be even fainter. Perhaps most interestingly, a subset of faint, uncorrelated detections are rapidly tumbling such that they straddle the limiting magnitude of our observations over the course of a single exposure. These pose a rather complex issue due to the difficulty in obtaining an estimate of object size with such variation in brightness. We present a preliminary analysis based on light curves extracted from our sampled population of objects in the GEO regime. This work is part of an ongoing collaboration between the University of Warwick and the Defence Science & Technology Laboratory to investigate the population of faint geosynchronous debris.