Method and Apparatus for Precise Noncoherent Doppler Tracking of a Spacecraft
A method and apparatus are disclosed for making precise velocity measurements of a spacecraft using a two-way noncoherent Doppler tracking system. The received uplink and transmitted downlink frequencies onboard the spacecraft are compared with the resulting information being included in the downlink signal and used to cancel spacecraft oscillator drift rate effects in the two-way Doppler measurement made by the ground station. The information can be also be used to characterize the drift rate of the spacecraft oscillator, thus permitting periods of accurate one-way Doppler tracking by the ground station. To improve accuracy, the times at which the measurements comprising the information would have been observed on the ground are inferred from the measurement of a signal generated by the spacecraft, e.g., the telemetry frame start times, made by the ground station.
Patent Status: U.S. patent(s) 5,995,039 issued.CONTACT:
Mr. E. Chalfin
Phone: (443) 778-7473