1. A method of autonomous space navigation, comprising: from a tracker space vehicle in a first trajectory through a gravitational field about a gravitational body, making a series of line-of-sight (LOS) measurements in an inertial frame of reference of a target space vehicle in a second trajectory through the gravitational field producing a unique inertial LOS history; providing an extended Kalman filter (EKF) based on a gravity model for said gravitational body and including a first set of states for the target space vehicle and a second set of states for the tracker space vehicle; inputting only the unique LOS history and time into the EKF that updates said first and second sets of states to simultaneously infer position and velocity relative to the inertial frame of reference for both the target and tracker space vehicles; and outputting the position and velocity for at least one of said target and tracker space vehicles.