ROBUST ACCURATE GPS TIME REFERENCE FOR SPACE APPLICATION

摘要

A receiver clock bias signal (13) for a spacecraft in motion is used to obtain a real-time navigation filter (14) solution of the clock bias and provide a robust accurate GPS time reference, even when there are less than four GPS satellites (9) within the view of the receiver in the spacecraft. The Kalman filter of the spacecraft provides an accurate solution of the clock bias (17), with less than four GPS satellite signals, by means of system which uses the knowledge of the dynamic motion of the satellite (4) in conjunction with GPS signals for a robust estimation of time. The system provides an accurate GPS time reference by transferring timing information from an atomic reference standard (GPS) (12) to a spacecraft in motion by directly measuring the GPS signal without depending upon the tracking of multiple GPS satellites or a static receiver. Implementation is current aerospace qualified GPS receivers, e.g., the "GPS TENSOR", and known orbital dynamics (8) are used to predict receiver position which aids in the transfer of the GPS time.