Onboard clock correction by means of drift prediction
AssigneeCommunications Satellite Corporation
InventorThomas Inukai
Life of this patent
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Abstract
In an on-board satellite clock correction system of the type wherein phase errors between the satellite clock and a ground-based clock are determined and a clock correction value sent to the satellite, the clock correction value is determined by curve-fitting the determined phase errors in accordance with a polynomial function, updating the polynomial function coefficients so as to minimize discrepancy between the determined phase errors and those according to the polynomial function, predicting a clock drift in accordance with the polynomial function and calculating an error correction value in accordance with the predicted clock drift.
Claims14
In a method of operating a clock system, said method of the type comprising the steps of transmitting metering bursts to a satellite, determining an amount of phase error in an onboard clock of said satellite in response to re-transmitted bursts received from said satellite, and generating and transmitting to said satellite an error correction value for correcting said error in said onboard clock relative to said metering bursts, the improvement characterised in that said generating step comprises the steps of:
- curve-fitting said determined phase errors in accordance with a polynomial function having coefficient values including adjusting said coefficient values in order to minimize an error between said determined phase errors and phase errors predicted in accordance with said polynomial function;
- predicting an amount of clock drift in accordance with said polynomial function;
- and
- calculating said error correction value in accordance with said predicted amount of drift.
A satellite clock system of the type comprising means for transmitting metering bursts to a satellite;
- means for determining an amount of phase error in an onboard clock of said satellite in response to re-transmitted bursts received from said satellite, and error correction means for generating and transmitting to said satellite an error correction value for correcting said error in said onboard clock relative to said metering bursts, the improvement characterized in that said error correction means comprises:
- clock correction algorithm processing means for curve-fitting said determined phase errors according to a polynomial function having coefficients, said algorithm processing means adjusting the values of said coefficients in order to minimize an error between said determined phase errors and results of said polynomial function, determining a predicted clock drift in accordance with said polynomial function and calculating said error correction value in accordance with said predicted clock drift.
Dependencies are inferred from the claim text.