| 摘要 |
A satellite communication system has at least one satellite (1) with an antenna that generates a moving beam pattern on the surface of the earth. The beam pattern (3) is comprises a plurality of sub-beams (4). A method of this invention determines an attitude correction signal for the satellite by the steps of providing at least one reference transmitter (10) at a known location on the surface of the earth transmitting at least one signal from the at least one reference transmitter into at least one of the subbeams receiving the at least one signal with the satellite antenna and transponding the received at least one signal to a ground station (8). Next, the transponded at least one signal is received by the ground station which determines a gain of the received at least one signal, compares the determined gain to a gain expected to be received based on a predetermined knowledge of a spatial variation in gain of the satellite antenna and determines a difference between the determined gain and the expected gain to derive a correction signal indicative of an attitude error of the satellite. The correction signal is then transmitted to the satellite and the attitude of the satellite is corrected in accordance with the correction signal. For the case where the correction signal has a value that is a function of yaw error angle of the satellite, the method further includes the steps of transmitting the correction signal to the satellite and correcting the attitude of the satellite in accordance with the correction signal by rotating the satellite about the yaw axis so as to reduce a magnitude of the yaw error angle. <IMAGE> |
