Software has been developed for the SAINT program that simulates the operation of a Fourier Telescopy imaging system that could potentially be used to create images of a satellite in low earth orbit. Fourier telescopy uses multiple beams that illuminate the target with a fringe pattern that sweeps across it due to frequency differences between beams. In this way the target spatial frequency components are encoded in the temporal signal that is reflected from the target. The software simulates the propagation effects and target interaction effects that would be present in a real system. This enables the creation of a simulated received signal as a function of time. A particular problem was accurately modeling the appearance of the target as its aspect changes during a rapid transit over the transmitter and receiver. A novel reconstructor has been developed that compensates for atmospheric phase fluctuations affecting the large number of beams transmitted simultaneously( ~10). The reconstructor solves for hundreds of image Fourier components simultaneously, permitting rapid reconstruction of the image.
We report on the operation and performance of an integrated 1 m adaptive optics system for compensation of atmospheric distortion of optical wavefronts. Both visible artificial laser guide stars (doubled Nd:Yag laser with wavelength of 0.532 rim) and natural stars can be used as sources for reference wavefronts. A shearing interferometer which uses a narrow optical bandwidth and has 500 subapertures is employed to sense wavefront distortion. These measurements are used to compute a conjugate wavefront to the distorted input light. The computed conjugate is then imprinted on a deformable mirror which consists of 500 square mirror segments. The effectiveness of the compensation is determined from a measured PSF of the system. Both indoor benchtop and atmospheric experiments are under way to test the performance of the integrated system.The results of these initial tests are very promising, yielding short-exposure images at 0.532 microns which contain discernible energy at the diffraction limit of 0. 1 arcsec.
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