Spacecraft Attitude Measurement Using Spatial Coherence of Laser or Star Light

A new method of measuring the attitude of spacecraft with respect to a reference beam of laser light or star light is described. The method uses the spatial coherence property of these beams and provides accuracies of ± 0.01 second of arc or greater. After giving a general description of the method, the feasibility of constructing such systems using presently available lasers and detectors is established. Finally, some aspects of the detection equipment are examined in detail.