Midcourse Space Experiment Satellite Flight Measurements of Contaminants on Quartz Crystal Microbalances

摘要

The Midcourse Space Experiment (MSX) is a Ballistic Missile Defense Organization demonstration and validation satellite program that has both defense and civilian applications. MSX was launched on April 24, 1996, and has uv, visible, and infrared instruments including the Space Infrared Imaging Telescope (Spirit 3) cryogenic telescope. MSX had several contamination-measuring instruments to monitor pressure, gas species, water and particulate concentrations, and condensable gas species. A cryogenic quartz crystal microbalance (CQCM) and four temperature-controlled quartz crystal microbalances (TQCMs) were part of this suite of contamination-measuring instruments onboard the satellite. The CQCM was located internal to the Spirit 3 cryogenic telescope and was mounted adjacent to the primary mirror. The CQCM provided a real-time monitor of contaminant mass deposition on the primary mirror, which was cooled to the same temperature as the mirror, ～20 K. Thermogravimetric analyses on the CQCM provided insight into the amount and species of contaminants condensed at various stages of the mission. The four TQCMs were positioned strategically on the outside of the spacecraft and operated at approximately -50℃ to monitor the silicone and organic contaminant flux deposition on external surfaces at specific locations. During the first week of flight operation, all TQCMs recorded deposition rates in the 10-20-ng/cm~2-day (1-2-A/day) range. 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 A/day, depending on TQCM location.