Coarse alignment of lunar exploration rover using accelerometer and sun sensor

Lunar rover plays a key role in lunar exploration based on its maneuverability. For the successful operation of the lunar rover, a high-accuracy navigation technique has to be obtained. In order to perform high-accuracy inertial navigation, the accuracy of initial alignment is important. In general, initial alignment can be divided into two processes, coarse and fine alignment. In the general coarse alignment process, the acceleration and rotation rate of the stationary rover are used as reference vectors. However, the acceleration and rotation rate of the Moon are 1/6 and 1/27 times smaller than those of the Earth, respectively. As a result, even though the same sensors are used, the performance of initial coarse alignment gets worse on the Moon. In this paper, three coarse alignment methods using accelerometers and sun sensor, instead of accelerometers and gyros, are proposed and the associated errors are analyzed. For comparison, the existing general coarse alignment algorithms are summarized. The analyses are verified by appropriate computer simulations, and it shows that the proposed algorithms greatly improve the performance of coarse alignment, outperforming the existing algorithms at least on the Moon. Therefore, the proposed algorithm is suitable for lunar rover application, and can also be applied to other planetary explorations.