Engineering:Corrective Optics Space Telescope Axial Replacement

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The Corrective Optics Space Telescope Axial Replacement (COSTAR) is the instrument designed to correct Hubble Space Telescope's spherical aberration for light focused at the FOC, FOS and GHRS instruments.[1] Built by Ball Aerospace Corp., it replaced the High Speed Photometer (HSP) during the first Hubble Servicing Mission in 1993.[2]

Later instruments, installed after HST's initial deployment, were designed with their own corrective optics. COSTAR was removed from HST in 2009 during the fifth servicing mission and replaced by the Cosmic Origins Spectrograph. It is now on exhibit in the Smithsonian's National Air and Space Museum.[3]


Figure 4 from the NASA report "A Strategy for Recovery": THE CORRECTOR SYSTEM proposed for the FOC, HRS and FOS consists of two mirrors, M1 and M2 (Figure 4). M1 forms an image of the OTA pupil at M2 and an image of the OTA field between the mirrors. The latter image is relayed by M2 to the SI aperture. M1 has the function of a field mirror and is a simple sphere. The correction of spherical aberration is done by M2 and is fully equivalent to correction at the OTA primary mirror itself. This feature is unique among the SI-external optical corrector systems considered in this report. It has the advantage that the corrected field is free of coma.[4]

In space



  1. James H. Crocker (1993). "Engineering the COSTAR". Optics & Photonics News 4 (11). 
  3. "Camera That Saved Hubble Now On Display". NPR. November 18, 2009. 
  4. Brown, R.A.; H.C. Ford (1990). Report of the HST Strategy Panel: A Strategy for Recovery (PDF) (Technical report). NASA. CR-187826.

External links Optics Space Telescope Axial Replacement was the original source. Read more.