If you’re looking for a working example of using GNU Radio, check it out [Daniel Estévez’s] Work to decode captured telemetry From the cubes of the moon flashlight. Cubes is You are facing some problems, but the data in question was a recording from the day after launch. We’re not sure what it would take to eavesdrop directly on it, but the 3-minute recording comes from a 20m antenna at 8.4GHz.
the Radio GNU flowchart Not as bad as you might think, thanks to some judicious reuse of blocks from other projects to do some decoding. The modification is PCM / PM / biphasic-L. Nominally, the speed is supposed to be 48000 baud, but [Daniel] Measuring 48,077.
Telemetry is often used on spacecraft CCSDS (Advisory Committee on Space Data Systems), and the encryption conforms to the standard. One weird thing is that halfway through the recording, the carrier frequency jumps above 120kHz. [Daniel] He speculates that the satellite was correcting its frequency to lock onto an uplink carrier from an earth station.
Once you dump the data, you have to interpret it, and [Daniel] Does a good job using Jupyter. He doesn’t know the full coordination of all the telemetry operations, but he makes some assumptions that seem sound. We have to wonder how the analyzes compare to the official JPL ground station.
The last time we checked in with Daniel, he did the same trick Voyager I. If you want to try GNU Radio – even if you don’t have any radio equipment – check this out Introduction.
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