Spacecraft disciplined reference oscillator
First Claim
1. A method for synchronizing an earth orbit satellite to a Global Positioning System (GPS), comprising the steps of:
- receiving a reference timing pulse from the GPS;
phase locking a reference oscillator of the satellite to the received GPS reference timing pulse; and
continuously and automatically correcting the phase and frequency of the reference oscillator in order to maintain synchronization between the satellite and the GPS;
wherein the step of continuously and automatically correcting the reference oscillator is selectively modified based on commands from a terrestrial control system so as to employ at least one of a value stored on the satellite or a value transmitted from the terrestrial control system.
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Abstract
An earth orbit satellite control system which provides automatic, continuous correction of phase and frequency in order to maintain synchronization between the satellite and a Global Positioning System (GPS). The system achieves phase and frequency synchronization by disciplining the satellite'"'"'s reference oscillator by phase locking it to timing pulses received from the GPS. The system comprising a state machine controller which cycles the disciplined oscillator into both a closed-loop operation wherein the oscillator is phase-locked to the GPS timing pulses, and an open-loop operation wherein a previously stored GPS timing pulse, or commands from a ground station, drive oscillator phase and frequency synchronization.
51 Citations
29 Claims
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1. A method for synchronizing an earth orbit satellite to a Global Positioning System (GPS), comprising the steps of:
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receiving a reference timing pulse from the GPS; phase locking a reference oscillator of the satellite to the received GPS reference timing pulse; and continuously and automatically correcting the phase and frequency of the reference oscillator in order to maintain synchronization between the satellite and the GPS; wherein the step of continuously and automatically correcting the reference oscillator is selectively modified based on commands from a terrestrial control system so as to employ at least one of a value stored on the satellite or a value transmitted from the terrestrial control system. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A satellite synchronization system, comprising:
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a reference oscillator located on board a satellite; a receiver for receiving GPS reference timing pulses, said receiver coupled to said reference oscillator; means in said satellite for synchronizing said reference oscillator to said received GPS reference timing pulses; and means in said satellite for continuously and automatically correcting the phase and frequency of said reference oscillator in order to maintain synchronization between said satellite and said GPS, wherein in response to commands from a terrestrial control system said means for correcting selectively employ at least one of a value stored on the satellite or a value transmitted from said terrestrial control system. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28)
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29. A satellite synchronization system, comprising:
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a reference oscillator on board a satellite; at least one GPS timing pulse receiver coupled to said reference oscillator; means in said satellite for synchronizing said reference oscillator to received GPS reference timing pulses; means in said satellite for continuously and automatically correcting the phase and frequency of said reference oscillator in order to maintain synchronization between said satellite and said GPS; and a manual control which accepts commands from a ground station to override said synchronizing of said reference oscillator to said received GPS reference timing pulses, and instead to enable ground-based commands to control said satellite'"'"'s reference oscillator.
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Specification