Corrective Optics Space Telescope Axial Replacement (COSTAR)
Ball Aerospace built the Corrective Optics Space Telescope Axial Replacement (COSTAR), which corrected a spherical aberration in the Hubble Space Telescope’s primary mirror. The aberration inhibited Hubble’s ability to properly focus light. Known as “the eyeglasses for Hubble,” COSTAR restored the telescope's imaging capabilities during the first servicing mission in 1993.
COSTAR made the imaging performance of Hubble close to the theoretical optimum, allowing observations to be made with the full sensitivity and resolution for which Hubble was designed.
Servicing Mission 4 Activities
Astronauts removed COSTAR during the final servicing mission in 2009. New instruments incorporate an internal correcting optical system based on COSTAR’s successful design.