Qualification of CO2 jet spray cleaning for use on magnesium-fluoride-protected aluminum coatings for the corrective optics space telescope axial replacement (COSTAR)

John G. Hagopian; Charles M. Fleetwood; Ritva A. M. Keski-Kuha; Douglas B. Leviton; Geraldine A. Wright; Charles W. Bowers

doi:10.1117/12.190154

19 October 1994 Qualification of CO2 jet spray cleaning for use on magnesium-fluoride-protected aluminum coatings for the corrective optics space telescope axial replacement (COSTAR)

John G. Hagopian, Charles M. Fleetwood, Ritva A. M. Keski-Kuha, Douglas B. Leviton, Geraldine A. Wright, Charles W. Bowers

Author Affiliations +

Proceedings Volume 2261, Optical System Contamination: Effects, Measurements, and Control IV; (1994) https://doi.org/10.1117/12.190154
Event: SPIE's 1994 International Symposium on Optics, Imaging, and Instrumentation, 1994, San Diego, CA, United States

Abstract

Low level particulate contamination of some of the COSTAR optics during environmental testing necessitated the development of a short duration, low pressure CO₂ jet spray cleaning technique. The technique was proven to be compatible with the high reflectivity UV magnesium fluoride protected aluminum coatings applied to the COSTAR optics at the Goddard Space Flight Center (GSFC). These coatings are easily damaged by solvent flush techniques in the presence of this contamination and by conventional CO₂ jet spray cleaning methods. In addition, the technique adopted here was compatible with the geometry of the fully integrated and aligned optics on the COSTAR. Eventually, thorough testing of intentionally contaminated test mirrors and a final UV throughput test of the flight optics indicated that the instrument would still meet specifications, therefore the COSTAR flight optics were not cleaned. However, we proceeded with the qualification of the process so that it would be available for use if cleaning became necessary prior to launch. Success criteria for the cleaning included minimal degradation of reflectivity, surface roughness, near-angle scattering, minimal production of pinholes in the coating, compatibility with the polyurethane bond applied to the optics and high efficiency of particulate removal. The technique was qualified for COSTAR specific coatings and particulate contamination and should be recertified for conditions departing from those baselined in our study.

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John G. Hagopian, Charles M. Fleetwood, Ritva A. M. Keski-Kuha, Douglas B. Leviton, Geraldine A. Wright, and Charles W. Bowers "Qualification of CO2 jet spray cleaning for use on magnesium-fluoride-protected aluminum coatings for the corrective optics space telescope axial replacement (COSTAR)", Proc. SPIE 2261, Optical System Contamination: Effects, Measurements, and Control IV, (19 October 1994); https://doi.org/10.1117/12.190154

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KEYWORDS

Mirrors

Contamination

Optical coatings

Reflectivity

Carbon dioxide

Optical testing

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