LOCAL ENVIRONMENT SURROUNDING THE MIDCOURSE SPACE EXPERIMENT SATELLITE DURING ITS FIRST WEEK

The environment measured surrounding the complex Midcourse Space Exper iment spacecraft during its first week on orbit is reported. A suite o f instruments including a pressure sensor, a neutral and an ion mass s pectrometer, quartz crystal microbalances, and flashlamp-based water a nd particle detectors were activated within hours after launch. These instruments measured the gaseous composition, particulate, and film ac cretion temporal histories. Spacecraft environment cleanliness and res ponse to operational activities were used to guide decisions about sen sor operation. As a result of careful material selection and ground pr eparation procedures, the measured levels of condensible species were sufficiently low to permit Safe sensor operation after only a few days in orbit.