Installing an optical telescope (COSTAR) on Hubble

One of Hubble's 'eyes', the Corrective Optics Space Telescope Axial Replacement (COSTAR) being installed on the Hubble Space Telescope. COSTAR is not really a science instrument; it is a corrective optics package that displaced the High Speed Photometer (HSP) during the first servicing mission. COSTAR is designed to optically correct the effects of the primary mirror's aberration on the Faint Object Camera (FOC). All the other instruments, installed since HST's initial deployment, were designed with their own corrective optics.