<title>Reduction of flight hardware outgassing after integration under a less stringent requirement</title>

Abstract

In preparation for the Hubble Space Telescope (HST) second servicing mission, hardware which was assembled a decade earlier was refurbished and cleaned to meet a requirement more than an order of magnitude cleaner than the original requirement. The fine guidance sensor (FGS) radial bay module is located in ]close proximity to the HST science instruments; therefore the condemnation sensitivity of the second servicing mission science instruments necessitated the establishment of new FGS contamination requirements. These new requirements are based on a critical optics temperature of minus 88 degrees Celsius; the original FGS outgassing requirements were based on protecting the HST primary mirror, which has an average temperature of plus 10 degrees Celsius. A contamination reduction plan was devised, implemented, and refined, resulting in partial deintegration of the FGS, the use of molecular adsorbers, and the use of a bakeout temperature within 1 degree of Celsius of the maximum survival temperature of the hardware. Final contamination measurements are within 3% of the predicted levels and meet the second servicing mission contamination requirements.