Ivan B. Steiner

Next generation space telescope: control system issues

The control system requirements for the next generation space telescope are discussed, based on the authors experience with Hubble Space Telescope (HST), Advanced X-Ray Astrophysics Facility (AXAF) and Space Infrared Telescope Facility (SIRTF). Since the HST design phase, there have been significant strides in the guidance and control domain (i.e., fiber optic gyroscopes, solid state star trackers and non-linear control algorithms). The control system design will be determined by the predicted spacecraft configuration, mirror geometry (6 to 8 meters will be considered) and science requirements. Spacecraft dimensions have been estimated for the telescope aperture range of interest. Presently, the Energiya rocket can only accommodate a 6 m telescope, the proposed Heavy Lift Launch Vehicle apparently can accommodate a 7 m telescope. A low Earth orbit (600 Km) has been adopted for this study, the advantage of Shuttle servicing and an accompanying long spacecraft life, weighed heavily in this decision. However, the possibility of a long spacecraft life in a high altitude orbit, with the requisite attitude control redundancy and fault tolerance, may be feasible.