If you’ve been wanting for a realistic illustration of utilizing GNU Radio, you really should look at out [Daniel Estévez’s] operate on decoding telemetry captured from the Lunar Flashlight cubesat. The cubesat is obtaining some difficulties, but the knowledge in dilemma was a recording from the day right after launch. We aren’t absolutely sure what it would just take to eavesdrop on it are living, but the 3-minute recording is from a 20-meter antenna at 8.4 GHz.
The flowgraph for GNU Radio is not as undesirable as you may imagine, thanks to some even handed reuse of blocks from other assignments to do some of the decoding. The modulation is PCM/PM/bi-section-L. Nominally, the velocity is supposed to be 48,000 baud, but [Daniel] measured 48,077.
Spacecraft telemetry generally works by using the CCSDS (Consultative Committee for Place Facts Devices) common, and the encoding matches the common. Just one oddity is that midway by way of the recording, the carrier frequency jumps above 120 kHz. [Daniel] speculates that the satellite was correcting its frequency to lock to an uplink carrier from a ground station.
At the time the information is unpacked, you have to interpret it, and [Daniel] does a excellent occupation utilizing Jupyter. He doesn’t know the total structure of all the telemetry, but he helps make some assumptions that feel sound. We have to wonder how the analytics look at with JPL’s formal ground station.
The previous time we checked in with Daniel, he did the exact trick for Voyager I. If you want to check out GNU Radio — even if you never have any radio hardware — check out our introduction.