An Innovative Approach to Determine the Alignment of the Star Camera System for the Clementine Spacecraft

The Clementine spacecraft has the requirement to provide accurate inertial pointing of the mission sensors toward celestial objects, perform precisely-oriented propulsion maneuvers, and steer the body-fixed high-gain downlink antenna. The baseline for the spacecraft's inertial knowledge is derived from the on-board star camera system. This paper describes the methods employed to derive the critical alignment of the two star cameras with respect to the spacecraft. The primary alignment combined conventional optical metrology to orient the star cameras relative to the spacecraft axes with outdoor alignment of the star cameras using the night sky. The end-to-end verification of the fully-integrated spacecraft was done entirely using the night sky. These techniques were unique in that they were designed to provide a fast, accurate, and complete end-to-end alignment without costly and time-consuming hardware and test fixture setups.