Guidance method for braking phase of lunar lander

A study demonstrates the guidance method for the main braking phase of the lunar soft landing. First, a reasonable target orbit is designed for connecting the landing point and the perilune of the parking orbit. According to the orbital transfer with the finite thrust and the terminal constraints of orbital elements, the guidance commands are then proposed for braking. The least-squares algorithm is used to obtain the true values of the guidance commands that satisfy terminal constraints. The proposed guidance algorithm is autonomous for the lunar lander conveniently due to its advantages of high speed of iteration and a simple form.