The phase-front distortion of laser radiation propagating through the turbulent atmosphere has been measured simultaneously at several wavelengths in the visible using a long-range Mach-Zehnder interferometer with high spatial and temporal resolution (476 nm

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Geosynchronous satellites are often required to maintain accurately their orientation with respect to a selected point at the earth surface. Precise attitude determination of these satellites may be achieved using a laser beacon from ground to the satellite as a directional reference. Four simple implementations of this principle are analyzed, and the influence of the cloudy atmosphere on the laser beacon and, therefore, on the accuracy of the method is discussed. All-weather operation is not possible; for normal cloudiness conditions, however, two analyzed systems (pulsed Nd:YAG laser with photomultiplier and CO(2) laser with cryogenic detector) appear to be feasible.

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