Telescope phasing by simulated annealing

We have used a laser interferometer to measure the relative optical pathlength variations from the focal plane to the six individual secondary telescopes of the Multiple Mirror Telescope (MMT). These pathlengths vary as func- Lions of elevation due to variable gravitational loading, drive acceleration and velocity, temperature variations, and wind loading. Vibrations induced by wind loading and telescope drives, including building vibrations transmitted to the mount, cause high-frequency variations in the otherwise slowly varying optical pathlengths. This experiment was designed to evaluate the effects of these high-frequency perturbations on optical interferometry at various tracking rates, including those relevant to Earth Satellite observation. We find effects which can strongly affect the contrast of interferograms.