A Smooth Nadir-Pointing Attitude Guidance law for Satellites Constrained by the Deviation of Sun-Pointing

This paper proposes a novel nadir-pointing guidance method for satellites constrained by the deviation of sun-pointing, to ensure the attitude of the satellite steering smoothly. The main idea of establishing the expected attitude contains two steps. Firstly, establishing a temporary attitude according to the nadir direction and the normal direction of the ecliptic. Secondly, in order to reduce the deviation between the expected Sun-pointing axis and the Sun-pointing direction, the temporary attitude will be rotated along one Euler axis, and ensure that the expected nadir-pointing axis fixed in the nadir direction at the same time. The nadir-pointing method provided in this paper overcomes the singular phenomenon that the expected attitude of the satellite flips, without serious loss of Sun-pointing. In this way, the peak expected angular velocity and the peak power consumption will be greatly reduced.