Reflective Correctors for the HST Axial Instruments

Abstract

Soon after it was established that the spherical aberration in the HST was due to excessive asphericity of the primary mirror, a group of astronomers and optical experts was formed (the HST Strategy Panel*) to investigate possible means of correction. After reviewing some twenty-five different ideas, the Strategy Panel recommended individual reflective correctors for three of the axial scientific instruments (ASI), namely, the Faint Object Camera (FOC), the Faint Object Spectrograph (FOS), and the Goddard High Resolution Spectrograph (GHRS), be installed during the first scheduled refurbishment mission. The fourth ASI, the High Speed Photometer (HSP), was to be replaced by a new module, the Corrector Optics Space Telescope Axial Replacement (COSTAR), to form a basis for deployment of the corrector systems. Replacement in the same mission of the fifth instrument, the Wide Field and Planetary Camera (WF/PC) by a new version was already planned by NASA. Its optics are modified to compensate the spherical aberration internally.