(US5257759-A)      The system maintains a desirable orientation of the solar wings of an orbiting satellite (10) relative to the sun. A dual array of sun sensors (26,28) is positioned on a body (12) of the satellite in order to get a measurement of the position of the sun relative to the body once per every orbit of the satellite.    In addition, an estimate of the position of the solar wings (16, 17) relative to the body of the satellite is attained. The sun-to-body angle is then subtracted from the body-to-wing angle to drive an error signal which is applied to a wing driver mechanism in order to maintain the solar wings (16,17) of the satellite in a proper orientation relative to the sun.    USE -   For controlling position of solar wings on satellite.    (EP544198-B1)      A system for maintaining a desirable orientation of at least one solar wing (16; 17) of an orbiting satellite (10) relative to the sun (22), said satellite (10) including a satellite body (12; 30), said system comprising:    driver means (32, 34) for driving the at least one solar wing (16; 17), characterized by    said satellite body (12; 30) having at least one slit sun sensor to provide a measured satellite body to sun angle beta sun once per orbit of the satellite (10);    sun tracking estimator means (36) for estimating the position of the satellite body (12; 30) relative to the sun (22) to drive a body-to-sun angle ? bs;    wing estimator means (42) for estimating the position of the at least one solar wing (16; 17) relative to the satellite body (12; 30) to derive a body-to-wing angle ? bw;    subtraction means for subtracting the estimate of the position of the satellite body (12; 30) to the sun (22) from the estimate of the position of the satellite body (12; 30) to the at least one solar wing (16; 17) to develop an error signal ? eee, and    control means (44, 46, 48, 50, 52) for providing a control signal relative to the error signal ? err to command the driver means (32; 34) to move the at least one wing (16; 17) to track the sun (22); and    wherein the derived body-to sun angle ? bs is updated with the measured body to sun angle beta sum once per orbit of the satellite (10).