A Survey of Electronic Attitude Measurement Systems

Introducing rectangular coordinates for the reference coordinate system and the space-vehicle fixed-coordinate system, it will be shown that the transformation matrixes between both coordinate systems which describe the attitude of the space vehicle can be easily computed as functions of the rectangular coordinates of two precise directions known in both coordinate systems. In detail, an electronic attitude measurement will be described based on two precise propagation directions of RF waves. In order to measure the propagation direction in the space-vehicle fixed-coordinate system, a very general interferometer is described. This interferometer is characterized by the fact that the antennas of the interferometer are arbitrarily distributed on the surface of the space vehicle and that the electronic computation of the coordinates of the propagation direction of an RF wave is extremely simple. The design and some modifications of this system are discussed