Corrective Optics Space Telescope Axial Replacement significant event STS-61
The Corrective Optics Space Telescope Axial Replacement (COSTAR) is an optical correction instrument designed and built by NASA. It was created to correct the spherical aberration of the Hubble Space Telescope's primary mirror, which incorrectly focused light upon the Faint Object Camera (FOC), Faint Object Spectrograph (FOS), and Goddard High Resolution Spectrograph (GHRS) instruments.It was flown via shuttle to the telescope in the servicing mission STS-61, on December 2, 1993, and successfully installed over a period of eleven days.