Spin Balance Processing of the Clementine Space Vehicle

The Clementine program was started in the spring of 1992 and launched on January 25, 1994. This fast-paced program served as a test-bed for several advanced lightweight sensor and component technologies developed by the Ballistic Missile Defense Organization. Using these technologies, the mission has provided digital imaging of the entire lunar surface for the planetary science community. Spin balance processing was one of the spacecraft processing activities affected by the fast-paced schedule of the Clementine program. Because of tight scheduling, complicated by safety constraints involved in the integration of a solid rocket motor (SRM), spin balance processing activities had to be tailored around the delivery of the SRM. Since the Payload Processing Facility of the Naval Research Laboratory is not approved for hazardous operations, spin balance processing required the flight SRM be replaced by a suitable substitute. Typically this would be accomplished with an inert version of the flight SRM. However, due to time and budget constraints, a "simple" mass simulator was chosen. The spacecraft-SRM mass simulator assembly and flight SRM were balanced separately. Following environmental testing and integration at the Naval Research Laboratory, the spacecraft was shipped to Vandenberg AFB for launch processing where a hazardous processing facility was available. The spacecraft was then integrated with the flight SRM and unbalance properties of the loaded assembly was successfully measured. By spin balancing major spacecraft components separately and substituting a mass simulator for the flight SRM, the Clementine processing schedule could be maintained while satisfying all SRM safety constraints. More importantly, final measured unbalanced properties of the spacecraft-flight SRM assembly were accurately determined and proven to be well within the requirements for the spacecraft attitude control system.