Patent ID: 7986265

Claim:
A method of estimating a rotational position of an object, the method comprising: prior to flight of the object during which the object spins, preloading the object from external to the object with initialization data, wherein the initialization data comprises information associated with a preloaded intended trajectory for the object, a preloaded space vehicle ephemeris data, and a preloaded system time of a satellite positioning system; initializing a timer based on the preloaded system time; during flight, maintaining a timer-based time via the timer without input from satellite positioning system signals; calculating line-of-sight (LOS) vectors based on the initialization data and the timer-based time; acquiring satellite positioning signals from a plurality of space vehicles and generating at least one of a correlated in-phase measurement or a correlated quadrature-phase measurement from each of the acquired plurality of satellite positioning signals; and determining a roll phase relative to each of the space vehicles corresponding to at least a selected group of the acquired plurality of satellite positioning signals by phase locking to an amplitude modulation of at least one of the correlated in-phase output signal or the correlated quadrature-phase output signal for each of the selected group of the acquired plurality of satellite positioning signals, wherein the amplitude modulation is caused by rolling of the object.