Design and Development of the Clementine Spacecraft Sensor Bench

The Clementine spacecraft was developed to demonstrate the performance of BMDO's lightweight sensor suite. The suite consisted of five different sensors (Star Trackers, UV/Vis, HiRes, NIR, LWIR) and a UDAR (Laser Impulse Detection And Ranging) system. The worst-case sensor operating requirements for the Clementine mission were: interface temperature with -20 to 2° C, alignment to +/- 100µRad, and jitter kept below 40 Rad in 40msec. The average hear dissipation of the suite was over 100 Watts while operating for two of the five hour lunar orbit. To accomplish the mission the sensor suite was integrated onto a single-substrate sensor bench within the spacecraft. The bench met the stringent thermal, alignment, and jitter requirements of the sensors, and concurrently isolated the sensors from outside spacecraft contamination, as well as thermal and structural flexure. Also taken into account were the mission design drivers of hot thermal environment in lunar orbit, limited volume in the spacecraft, minimal weight, limited budget, and a six month schedule from concept to delivery of a flight bench. The design and development of the sensor bench will be discussed. Three different types of heat pipes were used to transport the heat of the sensors to radiators located on the side of the spacecraft. A beryllium metal block was used as a thermal capacitor during peak heat loads. Thermal straps connected sensors to heat pipes to keep thermal gradients as little as 3° C per inch across the interface. The bench was fastened in a quasi-kinematic fashion to eliminate the transfer of spacecraft structural loads and thermal flexing, and yet was rigid enough to keep alignment through launch. The bench substrate itself was made out of aluminum honeycomb. The alignment mechanism consisted of a nut-on-nut method to attain and keep the 100µRad requirement. Volume and alignment constraints dictated sensor location on the bench. Development of the bench involved rigorous testing to insure requirements were met. These tests involved development alignment checks, vibration testing at the sensor bench level, system level qual vibes and TDVT, system level jitter testing, as well as the flight system vibe, TV AC and functional. Lessons learned will be discussed.