Cis-lunar Space Debris Radar Capability and Feasibility

Abstract

With NASA's new focus on returning to the Moon, there is a need to build the capability to detect and track objects or debris that may threaten future missions in cis-lunar space. This paper analyzes the feasibility of detecting and tracking objects in cis-lunar space using NASA's Deep Space Network's (DSN) Goldstone Solar System Radar (GSSR) and the Green Bank Telescope (GBT). The GSSR is a 70-m antenna that can transmit X-band signals at <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$450kW$</tex> . The cis-lunar space debris radar (CSDR) is a bistatic radar with the GSSR transmitting the signal and either the GBT (100-m diameter antenna) or a DSN 34-m antenna receiving the returned signal. The analysis will determine what object sizes are detectable under specific conditions and bistatic setups. Several GSSR, GBT, and DSN experiments were conducted to observe spacecraft in lunar orbit and xGEO (beyond GEO). The data from these experiments provide examples of detection versus tracking performance. Known spacecraft orbital dynamics will be compared with the radar estimated Dopplers, range, and signal-to-noise ratios (SNR). This analysis will look at the tradeoffs of waveforms traditionally used by GSSR, continuous wave (CW), and pseudorandom number (PN) codes and new ones considered for this application. With targets close to the Moon, return signals of certain waveform types are susceptible to interference from moon clutter.