MSX satellite - Flight measurements of contaminant films

Abstract

The Midcourse Space Experiment (MSX) satellite was launched on April 24, 1996. Earlier, descriptions of the Ballistic Missile Defense Organization (BMDO) satellite and some of the early results were presented. This paper provides an update of the data accumulated through the end of the cryo period. The cryo period included the time from launch through the lifetime of the SPIRIT 3 cryogenic telescope. This period covered about 10 months and ended when the dewar containing solid hydrogen warmed up to a temperature above 12 K. The five QCMs onboard the satellite provided data that have been invaluable in characterizing contamination levels around the spacecraft and inside the SPIRIT 3 cryogenic telescope. One of the QCMs, the CQCM, was located internal to the SPIRIT 3 cryogenic telescope and was mounted adjacent to the primary mirror. Real-time monitoring of contaminant mass deposition on the primary mirror was provided by the CQCM, which was cooled to the same temperature as the mirror — -20 K. Thermogravimetric analyses (TGAs) on the CQCM provided insight into the amount and species of contaminants condensed on the SPIRIT 3 primary mirror. The four TQCMs were mounted on the outside of the spacecraft for monitoring contaminant deposition on the external surfaces. The TQCMs operated at -50°C and were positioned strategically to monitor the silicone and organic contaminant flux arriving at specific locations. These TQCMs were located near the UV instruments or positioned to monitor mass coming from specific contaminant sources such as the solar panels. Updated time histories of contaminant thickness deposition for each of the QCMs are presented. Changes in contaminant deposition were seen during the SPIRIT 3 end of cryo warm-up, and implications will be discussed.