Determination of a spacecraft attitude using a ground-based laser.
Experiments for determining an element of attitude are analyzed and discussed to support a method of three-axes attitude determination of spacecraft using a ground-based laser. In this method, the third element, i.e., the angle around an axis connecting a given spacecraft to another station, is determined by means of the rotatory polarization of laser light. The accuracy of the element determination has been investigated in terms of the signal-to-noise ratio of laser light detection and the scintillation due to atmospheric turbulence. The results indicate that the accuracy is inversely proportional to the voltage signal-to-noise ratio (VSNR). The limit of accuracy is set by the choice of equipment. This limit is <0.1 degrees and is applicable for free space. When atmospheric transmission is included one must also consider the effect of scintillation. The relation between angular accuracy and the magnitude of scintillation is approximately linear in the region where the log-intensity fluctuation is smaller than ~0.25. Experiments suggest that accuracy <0.5 degrees over a 10-sec period (tau) would be obtained for laser transmission from earth to space given a VSNR higher than 100 and provided transmitting elevation is not too small. For other periods the value is inversely proportional to the square root of tau.
Aruga
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Ueda
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Igarashi
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