A Two-Mode INS/CNS Navigation Method for Lunar Rovers

A secure and autonomous navigation system is needed for the lunar rover in future lunar missions. The inertial navigation system (INS) and celestial navigation system (CNS) are two usually used autonomous navigation systems for rovers. Because INS and CNS are complementary to each other, INS/CNS integrated navigation becomes a very attractive solution for long-time and long-distance navigation. Traditional INS/CNS methods for aircrafts or ballistic missiles are not optimal for rovers because these methods only work in one motion state, but the rover operates in two motion states. For solving this problem, a two-mode INS/CNS navigation method for lunar rovers is presented in this paper. When the rover is stationary, a tightly coupled mode is used to correct the position and attitude of the rover. When the rover is in motion, a loosely coupled mode is used to correct the attitude of the rover. Two modes use different system models and different measurements to fulfill different targets and keep the error of position and attitude from accumulation. The validity and feasibility of the two-mode method is tested and examined by ground test system. The longitude and latitude errors within 50 m in distance can be achieved by this two-mode method during an 80-min traverse. These results demonstrate that it is a good choice of autonomous and high-accuracy navigation for lunar rovers.