A Terminal Descent Sensor Trade Study Overview for the Orion Landing and Recovery System

This trade study was conducted as a part of the Orion landing system advanced development project to determine possible terminal descent sensor (TDS) architectures that could be used for a rocket assisted landing system. Several technologies were considered for the Orion TDS including radar, lidar, GPS applications, mechanical sensors, and gamma ray altimetry. A preliminary down selection occurred by comparing each sensor´s ability to meet the requirements. The driving requirements included the range of operation, accuracy, and sensor development to a technology readiness level of 6 (TRL-6) by the Orion PDR in June 2008. Additionally, Orion is very mass and volume constrained, so these parameters were weighted heavily. Radar, lidar, and GPS applications all had potential to meet the requirements and were carried on for further analysis. Investigation into GPS led to concerns over potential loss of signal and required ground infrastructure, so GPS was taken out of the trade space. Remaining technologies included a pulse-Doppler radar, FMCW radar, and a hybrid lidar ranger and velocimeter (termed the hybrid lidar). The trade boils down to the maturity and weather robustness of the radar options versus the mass, volume, power, and heat shield blowout port size advantage of the lidar. This trade study did not result in a recommended TDS. The trade of the mass and volume impact versus the development time and cost should be made at a higher level than this particular trade study.