Towards Cis-Lunar Target Detection using the Deep Space Network and Open-Loop Tracking Measurements

As NASA and other space agencies are gearing up to return to the moon, there is significant interest and opportunities in detecting and tracking small objects, both man-made and otherwise, in cis-lunar space, a vast void between terrestrial orbits and the moon. This paper investigates the feasibility and performance of using NASA's Deep Space Network (DSN) tracking stations and the Goldstone Solar System Radar (GSSR), currently the world's most capable planetary radar transmitter, to detect and track Cis-Lunar targets. In 2022, the JPL GSSR team performed three Cis-Lunar radar experiments using DSN Open Loop Recorders (OLRs). Observations were made by illuminating the targets with continuous waveform (CW) and Pseudo Random Noise (PRN) codes at X-band with the 450kW transmitter on DSS-14, a 70-m diameter antenna at Goldstone, and detecting the targets' reflection echoes at DSS-13, DSN's 34-m diameter R&D antenna in Goldstone, CA, using an open-loop recording system. We evaluate the performance of Cis-Lunar target detection by comparing observations with the Doppler frequency estimates derived from spacecraft's orbital dynamics, lunar noise temperature impacts, Moon clutter effects, and Signal-to-Noise Ratio simulations. This investigation will improve our understanding of engineering and science constraints for future detection and tracking of Cis-Lunar targets, including satellites, debris, asteroids, and surface assets on the moon.