Hubble's Instruments: COSTAR - Corrective Optics Space Telescope Axial Replacement
COSTAR was not really a science instrument; it was a corrective optics package that displaced the High Speed Photometer (HSP) during the first servicing mission.
COSTAR was designed to optically correct the effects of the primary mirror's aberration on the Faint Object Camera (FOC), Goddard High Resolution Spectrograph (GHRS) and Faint Object Spectrograph (FOS).
All instruments installed since HST's initial deployment have been designed with built in corrective optics.
When the final first-generation instrument, FOC, was replaced by the Advanced Camera for Surveys (ACS) during Servicing Mission 3B, COSTAR was no longer needed.
COSTAR was removed and returned to Earth during Servicing Mission 4. Its instrument bay was then reused by COS, the Cosmic Origins Spectrograph.
COSTAR is now on display at the Smithsonian National Air and Space Museum in Washington DC.
COSTAR being inserted into Hubble during First Servicing Misson.
Two images taken of the same region before and after the correction of Hubble's aberration with COSTAR.