Analysis of Deviation Propagation for Translunar Free Return Orbit

Stability analysis of translunar free return orbit is significant for manned lunar mission orbit design and midcourse correction strategy programming. In this paper, a deviation propagation equation for free return orbit is derived in the synodic coordinate system. Based on the nominal orbit data and analysis method, the propagation law of orbit deviation is obtained. The simulation result indicates that the orbit deviation increases with the increasing fly time, and the deviation increased more quickly after the spacecraft orbiting the moon so that it could not return to the Earth. So the strict free return orbit in engineering is not existed, and the midcourse correction in earth-moon transfer fly is necessary.