The accuracy of the lunar UV sensor is limited by the oblate shape of the moon. The imaging principle of the lunar UV sensor and the geometry constraints when the sensor detecting the lunar horizon edge are investigated in this paper. Based on the imaging principle, a lunar nadir vector determination method is investigated. Compared with other approaches in previous literatures, the lunar oblateness is considered in this algorithm. Thereafter, a scenario of autonomous navigation for a lunar satellite based on orientation information of Sun-Moon-Earth is presented by using this algorithm to correct lunar oblateness. Simulation results show that the navigation position accuracy can achieve 300m (3σ) and velocity accuracy can achieve 0. 6m/s(3σ) under measurement noises of 0. 02°(3σ) for the sun sensor, 0. 05°(3σ) for the earth sensor, and 0. 1°(3σ) for the moon sensor, and ensures navigation accuracy of lunar satellite.%针对月球扁率对月球紫外敏感器的月心方向矢量确定的不利影响,研究了月球紫外敏感器的测量原理和敏感到月平边缘时满足的几何约束,提出了一种考虑月球扁率的月心矢量确定方法.并进一步的结合地球敏感器和太阳敏感器的测量信息,研究了基于日地月方位信息的月球卫星自主轨道算法,并评估了月球方位确定算法对导航精度的影响.仿真结果表明,在太阳敏感器、地球敏感器和月球敏感器的精度分别为0.02°(3σ)、0.05°(3σ)和0.1°(3σ)的假设下,考虑月球扁率修正的月球卫星的自主导航位置精度能达到300m(3σ),导航速度误差能达到0.6m/s(3σ),从而保证了环月卫星的导航精度.
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