Physics – Optics
Scientific paper
Sep 2000
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000spie.4096...11u&link_type=abstract
Proc. SPIE Vol. 4096, p. 11-20, Optical Systems Contamination and Degradation II: Effects, Measurements, and Control, Philip T.
Physics
Optics
Scientific paper
Outgassing experiments in space were conducted during the critical period in the cryogen lifetime of the large infrared telescope called Spatial Infrared Imager and Telescope (SPIRIT III) on the Midcourse Space Experiment (MSX) spacecraft. This was the period when the solid hydrogen in the dewar was being depleted and the optical components were warming up to evaporate previously condensed volatile materials. The volatile condensable materials were collected on the cryogenically cooled surfaces during the 4 months of prelaunch testing and the 10 months in orbit. The contamination instruments on board the spacecraft were used to monitor the outgassing of these materials. Besides contamination monitoring, it was also desired to control the heating or warm-up process without contaminating the still functioning UV and visible sensors. After considering several scenarios via thermal modeling, it was decided to conduct the warm-up period into two phases, with the first phase intended to approach but not exceed the sublimation point of ice on the primary mirror. Solar radiation was used to heat the SPIRIT III baffle and parts of the +Y face of the spacecraft while the contamination instruments were monitored the outgassing event. Ice redistribution from the baffle to the much colder primary mirror, as well as external pressure bursts and slight film depositions on quartz crystal microbalances were observed. The second phase of warm-up experiments again used solar heating to drive the telescope optics through the 150 K range for final sublimation of any ice remaining as well as condensed hydrocarbons from the cold primary mirror. The results of these end-of-cryo experiments are discussed in terms of the measured film deposits on the cryogenic quartz crystal microbalance and the pressures from the total pressure sensor.
Boies Mark T.
Cain Russell P.
Dyer James S.
Galica Gary E.
Green Byron David
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