Abstract: A celestial navigation system and method for determining a position of a vehicle. The system includes a star-tracker, a beam director, an inertial measurement unit, and a control module. The star-tracker has a field of view for capturing light. The beam director is configured to change a direction of the light captured in the field of view of the star-tracker. The inertial measurement unit has a plurality of sensors for measuring an acceleration and a rotation rate of the vehicle. The control module executes instructions to correct the attitude, the velocity and the position of the vehicle using the determined magnitude and position of the space objects. The control module also executes instructions to generate corrections to the IMU error parameters, the beam director and star-tracker alignment errors, and RSO ephemeris errors to achieve optimal performance.

Abstract: A celestial navigation system and method for determining a position of a vehicle. The system includes a star-tracker, a beam director, an inertial measurement unit, and a control module. The star-tracker has a field of view for capturing light. The beam director is configured to change a direction of the light captured in the field of view of the star-tracker. The inertial measurement unit has a plurality of sensors for measuring an acceleration and a rotation rate of the vehicle. The control module executes instructions to correct the attitude, the velocity and the position of the vehicle using the determined magnitude and position of the space objects. The control module also executes instructions to generate corrections to the IMU error parameters, the beam director and star-tracker alignment errors, and RSO ephemeris errors to achieve optimal performance.

Abstract: A global positioning system comprising: (a) a GPS receiver configured to (1) receive a plurality of signals from a plurality of visible GPS satellites, and (2) produce a plurality of pseudorange measurements from the received signals, the pseudorange measurements being indicative of the GPS receiver's position and having an amount of ionospheric delay error contained therein, (b) a processor configured to estimate the amount of ionospheric delay in the pseudorange measurements by (1) estimating an amount of global ionospheric delay attributable collectively to the plurality of visible GPS satellites, and (2) estimating a plurality of amounts of local ionospheric delays, each local ionospheric delay being attributable to a different visible GPS satellite. Preferably the processor implements the ionospheric delay estimations using a modified Kalman filter.

Abstract: A global positioning system comprising: (a) a GPS receiver configured to (1) receive a plurality of signals from a plurality of visible GPS satellites, and (2) produce a plurality of pseudorange measurements from the received signals, the pseudorange measurements being indicative of the GPS receiver's position and having an amount of ionospheric delay error contained therein; (b) a processor configured to estimate the amount of ionospheric delay in the pseudorange measurements by (1) estimating an amount of global ionospheric delay attributable collectively to the plurality of visible GPS satellites, and (2) estimating a plurality of amounts of local ionospheric delays, each local ionospheric delay being attributable to a different visible GPS satellite. Preferably the processor implements the ionospheric delay estimations using a modified Kalman filter.