Peter Zimmer, J. T. McGraw and Associates; John McGraw, J. T. McGraw and Associates; Mark Ackermann, J.T. McGraw and Associates, LLC
Keywords: Optical, SSA, Telescope, Debris, Faint
Abstract:
The first member satellites of the coming mega-constellations have launched, and over the next few years, LEO is going to get busy. Risks to new and existing missions are increasing geometrically. Optical observations can complement and augment radar surveillance, helping to derive and refine orbit elements, size and orientation estimates, and platform stability. Cued observations can refine these properties for known objects while blind surveillance can discover new or lost objects. Small optical telescopes, strategically distributed across the globe, will perform as needed in both cued and blind observing modes. Each of these will contribute to space situational awareness (SSA) and space traffic management (STM) missions.
This paper builds on the work we demonstrated at last years conference using a small, wide-field optical telescope to perform cued surveillance of various LEO objects. We extend that proof-of-concept work to a larger set of objects and observations, all with astrometry and photometry calibrated to GAIA DR2. The proof-of-concept work showed positive detections of fainter than 14th magnitude and sensitivity limits fainter than 15th magnitude, corresponding to diffuse black spheres of 10 cm and 6 cm diameter, respectively. There were, surprisingly, orientations of 1U cubesats that, dropped below that threshold for a few seconds and, unsurprisingly, glints that were 10,000 times brighter than that. In the case of cubesats, there usually are images of the craft in the public domain, so some range of spacecraft pose can be considered in explaining brightness variation. Fengyun 1C debris, which pervades the sky, is notoriously difficult to detect optically, let alone measure, and the sizes and shapes of these pieces are completely unknown. Thus, the larger sample will help answer questions about the discrepancies between radar cross-section-derived sizes and optical signature.
These observations will help constrain and refine models of expected photometric signals for LEO objects. Those models help inform the design and operation of optical telescope networks. This set of ongoing observations leads to the next step, which is routine operation of widely deployed systems automatically obtaining cued LEO observations.
Date of Conference: September 17-20, 2019
Track: Orbital Debris