A system for spacecraft attitude determination using laser techniques

The results of theoretical investigations and preliminary ground tests on a laser system for detecting the three parameters that determine the attitude of a satellite are reported. The principle by which a satellite receiving a laser signal from a ground station can orient itself properly is briefly explained, and the problems caused by cloud interference with the laser beam path are statistically examined. A qualitative presentation is made of how different kinds, heights, and thicknesses of cloud combined with laser beam divergences and wavelengths affect image pattern, polarization, and incident light intensity. The ground experiments used a reflector instead of a receiver. The equivalent propagation distance was 120 km; a horizontal path over a metallic building roof was selected in order to obtain intense scintillation. The results showed that an accuracy of better than 0.0001 rad is obtainable for the roll and pitch angles, and 0.01 rad or better for the yaw angle.