MIDCOURSE SPACE EXPERIMENT SATELLITE FLIGHT MEASUREMENTS OF CONTAMINANTS ON QUARTZ-CRYSTAL MICROBALANCES

The Midcourse Space Experiment (MSX) is a Ballistic Missile Defense Or ganization demonstration and validation satellite program that has bot h defense and civilian applications, MSX was launched on April 24, 199 6, and has uv, visible, and infrared instruments including the Space I nfrared Imaging Telescope (Spirit 3) cryogenic telescope, MSX had seve ral contamination-measuring instruments to monitor pressure, gas speci es, water and particulate concentrations, and condensable gas species, A cryogenic quartz crystal microbalance (CQCM) and four temperature-c ontrolled quartz crystal microbalances (TQCMs) were part of this suite of contamination-measuring instruments onboard the satellite. The CQC M was located internal to the Spirit 3 cryogenic telescope and was mou nted adjacent to the primary mirror. The CQCM provided a real-time mon itor of contaminant mass deposition on the primary mirror, which was c ooled to the same temperature as the mirror, similar to 20 K. Thermogr avimetric analyses on the CQCM provided insight into the amount and sp ecies of contaminants condensed at various stages of the mission. The four TQCMs were positioned strategically on the outside of the spacecr aft and operated at approximately -50 degrees C to monitor the silicon e and organic contaminant Bur deposition on external surfaces at speci fic locations. During the first week of flight operation, all TQCMs re corded deposition rates in the 10-20-ng/cm(2)-day (1-2-Angstrom/day) r ange, The measured deposition rates continuously decreased, and after 100 days into the mission the thickness deposition rates had fallen to values between 0 and 0.2 Angstrom/day, depending on TQCM location.