SEGMENTED SPACE TELESCOPE

Summary: We deploy a segmented and sparse telescope in space, and phase it using wide-band light from an extended object. A stochastic search for the sharpest image results in perfectly aligned segments.

Small observation satellites limit their telescope in mass and volume, and thus in resolution. Instead we use a larger segmented telescope, where the segments are sparse and thin The accuracy of segment placement is a small fraction of the wave length, so phasing after deployment is a major challenge.

Figure 1: Four segments of a parabolic mirror, focusing a collimated beam onto a camera. Twelve fine motors search for the optimal positions by iteratively improving the image.

We employ the image of the observed object, as a wave front sensor of sorts. We iteratively sharpen the white-light image by randomly moving the segments. The amount of average motion drops with decreasing virtual temperature, and the acceptance rate of images of lower sharpness drops similarly. Sharpness (or contrast) derives from the image standard deviation. The process time is a few hours, depending on the system complexity, and commensurate with the satellite deployment time.

Figure 2: (Left) Misaligned setup (seven degrees-of-freedom). (Right) After convergence, image is sharper.