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Substantial damage to the outer layer of Hubble Space Telescope (HST) thermal blankets was observed during the February 1997 servicing mission. After six years in low-earth orbit, many areas of the aluminized Teflon® outer blanket layer had significant cracks, and some material was peeled away to expose inner layers to solar flux. After the mission, the failure mechanism was determined, and repair materials and priorities were selected for follow-on missions. This paper focuses on the thermal design of the repair hardware and the creative solutions developed to meet thermal, mechanical, and EVA requirements. Hardware development, training, and on-orbit activities are also discussed.

A new, general-purpose computer program (BIFAC) has been developed for computing thermal radiant interchange among opaque surfaces that need not be perfectly diffuse or perfectly specular. The method uses the full bi-directional reflectance distribution function (BRDF) to determine directional radiosities, and thence heat fluxes, between surfaces. The method gives more accurate average interchange factors for diffuse surfaces, because it better represents interaction in corners. The maximum error in a stringent test using a specular surface was 8.9%, in great part because the exact specular solution does not include the real specular cone that is used in BIFAC.