<title>Incorporation of molecular adsorbers into future Hubble Space Telescope instruments</title>

Abstract

The Hubble Space Telescope (HST) has been designed to accommodate changeout and/or repair of many of the primary instruments and subsystem components, in an effort to prolong the useful life of this orbiting observatory. In order to achieve the science goals established for this observatory, many HST instruments must operate in regimes that are greatly influenced by the presence of on-orbit propagated contaminants. To insure that the required performance of each instrument is not compromised due to these contaminant effects, great efforts have been made to minimize the level of onorbit contamination. These efforts include careful material selection, performing extensive pre-flight vacuum bakeouts of parts and assemblies, assuring instrument assembly is carried out in strict cleanroom environments, performing precision cleaning of various parts, and most recently, the incorporation of a relatively new technology -Molecular Adsorbers, into the basic design of future replacement instruments.Molecular adsorbers were included as part of the Wide Field/Planetary Camera 2 (WFPC-2) instrument, which was integrated into the HST during the Servicing Mission 1 (SM1) in 1993. It is generally recognized that these adsorbers aided in the reduction of on-orbit contamination levels for the WFPC-2 instrument. This technology is now being implemented as part of the basic design for several new instruments being readied for the Servicing Mission 2 (5M2), scheduled for early 1997. An overview of the concept, design, applications, and to-date testing and predicted benefits associated with the molecular adsorbers within these new HST instruments will be presented and discussed in this paper. INTRODUCTIONThe HST program represents a major breakthrough in the development and launch of a multi-functional, large scale, space observatory system to study our universe. In conjunction with this ambitious goal has been implementation of a new space strategy for performing on-orbit servicing through the use of the Space Transport System. The updating of the spacecraft and instruments periodically with newer, better technology is accomplished during these servicing missions. This strategy has proven to be an effective and cost savings means of recycling, and renovating, and improving an existing orbiting spacecraft.In simple terms, the HST consists of a wide variety of complex optical systems, all merged together to form one orbiting astronomical observatory. HST was launched in 1990 and was designed for a 15 year mission lifetime, with the assumption that during those 1 5 years, the principal scientific instruments would be periodically updated, repaired, and/or replaced. To accomplish this goal, the program has been designed to include, periodic "servicing missions" to perform these spacecraft/instrument changes and to perform routine maintenance on critical spacecraft sub-systems.Many of the HST instruments include complex optical systems that have been designed to function on the assumption that only low levels of contamination will ...