The Midcourse Space Experiment (MSX) is a Ballistic Missile Defense Organization (BMDO) demonstration and validation satellite program that has both defense and civilian applications. MSX was launched April 24, 1996, and has UV, visible, and infrared instruments including the SPIRIT 3 (Space Infrared Imaging Telescope) cryogenic telescope. It also has several contamination measuring instruments for measuring pressure, gas species, water and particulate concentrations and condensable gas species. A cryogenic quartz crystal microbalance (CQCM) and four temperaturecontrolled microbalances (TQCMs) are part of this suite of contamination measuring instruments on board the satellite. This paper describes some of the flight QCM data obtained and analyzed to date. The CQCM is located internal to the SPIRIT 3 cryogenic telescope and is mounted adjacent to the primary mirror. Real-time monitoring of contaminant mass deposition on the primary mirror is being provided by the CQCM, which is cooled to the same temperature as the mirror-20 K. The four TQCMs are mounted on the outside of the spacecraft and monitor contaminant deposition on the external surfaces. The TQCMs operate at ~-50 C and are positioned strategically to monitor the silicone and organic contaminant flux arriving at specific locations, such as near to the UV instruments, or coming from specific contaminant sources such as the solar panels. Time histories of contaminant thickness deposition for each of the QCMs are presented. During the first week of flight operation, all * The research reported herein was performed by the Arnold Engineering Development Center (AEDC), Air Force Materiel Command. Work and analysis for this research were performed by personnel of Sverdrup Technology, Inc., AEDC Group, technical services contractor for AEDC. Further reproduction is authorized to satisfy needs of the U. S. Government.
Operation of thermal control and optical surfaces can be impaired by contamination deposition for spacebased systems. Determining the contamination level about the spacecraft and deposition of silicones and hydrocarbons will be studied during the flight of the Midcourse Space Experiment (MSX) Satellite that is scheduled for launch in 1994. The contaminants will be measured using four thermoelectrically cooled quartz crystal microbalances (TQCMs) which will be mounted on external spacecraft surfaces. Rigorous characterization and calibration measurements were made on six flight TQCMs at the Arnold Engineering Development Center at Arnold Air Force Base, TN. Since the TQCM output frequency depends to some degree on both the crystal temperature and the oscillator-mixer temperature, the magnitude of these effects and the effects of solar irradiation on the TQCMs was established. Long-term frequency drift rates were also determined. The change in TQCM output frequency expected to occur in space was, in some cases less than the magnitude of the frequency changes caused by temperature and solar fluctuations. The results of this study will allow a more accurate assessment of the contamination effects that can be expected during long-term space-flight programs. This program was sponsored by the Ballistic Missile Defense Organization (BMDO) through the Johns Hopkins University/Applied Physics Laboratory.
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