Study On Spacecraft Solar Panel Sun-tracking Method

With the development of space technology, power that spacecrafts require is increasing. Searching for solar array of larger power, higher reliability, longer life-span and lower cost is always one of the urgent requirements. In recent years, our country is engaged in developing satellites of large power for navigation and communication, with the problem of how to improve performances of the power system on board. Solar panel is widely used to provide energy for satellites. Orientation and sun tracking methods of solar panel of satellites in different orbits were discussed in this thesis, in favor of power system designation.Open-closed loop controlling was often used for sun tracking of solar panel of satellites in sun synchronous orbits, which keeps driving solar panel in a certain constant speed. The influence of sun movement and drag of atmosphere on the tracking error was analyzed, and a corresponding sun tracking method is derived.Yaw motion is a significant sun tracking method for satellites in a general inclined orbit with solar panels with single degree of freedom. A useful scheme which replaced the ideal yaw angle profile by a square wave has a great advantage for certain applications. The yaw angle is thus maintained constant for large parts of the orbit. An analytical formula of the constant optimal yaw angle as a function of the angle between the sun and the orbit was derived through polynomial curve fitting without incurring more power loss.Fixed solar panel can be used in satellites with low power, short life span and special application. A method for figuring out fixed solar array's optimal orientation is proposed in this paper for satellites in elliptic orbits, so that a maximum energy can be provided to the satellite. A theorem is proved, that is, the optimal orientation is in the direction of the centroid of the upper portion of the sun track cirque in the celestial sphere. With the theorem, the optimal orientation can be approximated by iteratively locating the corresponding centroid. This method is suitable for satellites in orbits of different eccentricities. Numerical simulations have demonstrated the effectiveness of the approach proposed.