An autonomous unmanned space
flight system and planetary lander executes a discrete landing sequence including performing an initial velocity braking maneuver to remove velocity at altitude, coasting during which the
planet surface is imaged and correlated to reference maps to estimate cross-track and along-track navigation errors and one or more lateral braking maneuvers are performed to reduce cross-track
navigation error, and performing a
terminal velocity braking maneuver(s) to reduce the along-track braking maneuver and remove the remainder of the velocity just prior to landing. A bi-
propellant propulsion
system provides a very high T / M ratio, at least 15:1 per
nozzle. Short, high T / M divert maneuvers provide the capability to remove cross-track
navigation error efficiently up to the maximum resolution of the reference maps. Short, high T / M
terminal velocity braking maneuver(s) provide the capability to remove along-track
navigation error to a similar resolution and remove the remaining velocity in a very short time window, approximately 3-15 seconds prior to touchdown. The
propulsive efficiency frees up
mass which can be allocated to a fuel to remove the unknown navigation errors, perform
hazard avoidance and / or relocate the lander by flying it to another site or be allocated to additional
payload.