Point Spread Function

5.3 Wavefront Quality

The conclusion of the extensive optical testing in thermal vacuum was that the cameras are well corrected to within the specifications. The measured wavefront errors in the four cameras were 1/30, 1/17, 1/40, and 1/21 waves at 6328Å. The dominant problem was a small difference in focus between the four cameras. The actuated fold mirrors and
pick-off mirror mechanism performed flawlessly in correcting residual coma aberrations in the image, and enabled the on-orbit alignment procedures. By defocusing the OTA secondary mirror, a very accurate alignment of the cameras was accomplished. A side effect was that the aberrations in each camera were measured (Krist and Burrows, Applied Optics, 1995). The results are given in Table 5.2. These values were used in generating the simulated PSFs given in section 5.5, "Model PSFs", on page 92.

Table 5.2: Aberrations in Each Camera.