Hardware and Software Implementation of Non-Coherent Navigation for Low Frame Rate Telemetry Applications
This invention is a method and apparatus for obtaining measurements, on a spacecraft that employs a transceiver, at intervals that are shorter than the telemetry frame duration for use in correcting ground-based Doppler measurements so as to remove the effects of drift in the spacecraft oscillator frequency reference. Samples of navigation counters on the spacecraft that supply information that may be used to compare the uplink frequency with the downlink frequency at the spacecraft are triggered at intervals that are shorter than the duration of a telemetry frame; the samples are then included in a telemetry frame and are time tagged after they are received on the ground; the time tagged samples are then used to calculate precise two-way Doppler measurements.
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