Steering low altitude satellite on particular path - is by optical sensor including photovoltaic cells producing correction signal

摘要

A low altitude satellite used for photographing the earth is kept on a particular path by ensuring the satellite axis maintains the trajectory axis in order to facilitate analysis of photographs. This is performed by an optical sensor using solar reflection. Photovoltaic cells (31,32) mounted behind grids receive signals dependent on speed parallel to trajectory axis and an angle of distant objects. The signals saturate amplifiers (41,42) and low pass filters (51,52) reduce the noise level. The signals are differentiated (61,62) and then detected and filtered (71,72) to produce a continuous voltage as a linear function of input signal frequency. A comparator (80) provides a correction signal which is a function of the angular error form the trajectory axis.