Hubble Space Telescope optics status

It is well known that the Hubble Space Telescope suffers from spherical aberration. Much that is scientifically valuable can be done with the telescope in its present condition, but we must install corrective optics. An analysis of images gives the same results as measurements on the equipment used to fabricate and test the primary mirror, so such optics can be designed with confidence, with a derived conic constant on the primary mirror of -1.0139(5). However, the optics assembly and integration with the spacecraft poses great challenges because if the corrected images are to be diffraction limited, they must be aligned to better than one percent of the beam diameter. Some other residual effects of the spherical aberration will remain after installation of the corrective optics, primarily in the pointing and collimation of the telescope. We summarize the present imaging performance of the observatory, and compare it with the expected performance when corrective optics (COSTAR and WFPC 2) are installed on-orbit.