SatNOGS is a great way for individuals tracking satellites to obtain telemetry from sites throughout the world, but apparently some of the ham satellite groups can’t get their telemetry directly from SatNOGS. Instead the users must download the audio files and upload them through the respective telemetry decoders. K2ZA and I spent some time today working out those processes, which are described below.
Install Audacity
Download and install the free Audacity program. You’ll use that to load the .ogg files that are exported from SatNOGS.
Download the .ogg files from SatNogs
Navigate to the SatNOGS observation that you want to use and download the audio file using the button below the radar track in the lower left part of the screen. This file will be formatted as a .ogg file. Neither the Fox nor Funcube programs can read these files – they’ll need to be converted or played back into the telemetry decoder.
Open the .ogg file in Audacity
Here’s how a Fox telemetry file appears in Audacity. If your output is set to your speakers you can play back the file as it was recorded. Our configuration below has the audio directed to a virtual audio cable, not to the speakers.
Fox: Export as a .WAV file
The Fox decoder can read a .wav file directly, so you’ll need to export the .ogg file as a .wav file using the Export command on the File menu. First, be sure to set the Project Rate to 44000 hz, since that’s what you’ll be using in the Fox telemetry program.
Fox: Open the .wav file in the telemetry decoder program
Set the Fox telemetry decoder program to AF and DUV and open the .wav file. The decoder will read this file much faster than realtime, and you can see the packets decoded in the framecount at the bottom of the screen. This appears to be the fastest way to send Fox telemetry from SatNOGS to the Fox warehouse.
Funcube: Play back the audio file through VAC into the Funcube telemetry program
For this you’ll need to have a Virtual Audio Cable program installed with at least one VAC set up. Set Audacity to output to the VAC (which we’ve done in the above Audacity screenshot) and set the Funcube telemetry program to input from that cable. Then “play” the audio file in Audacity – you’ll see it being decoded in the telemetry program. This is a lot slower than the Fox decoder, but it doesn’t appear that the Funcube decoder can directly read an audio file.
Next Steps
The next step, of course, is to script this process. It appears that Audacity allows scripting, and perhaps the telemetry decoders have command line interfaces that will allow piping the .wav or audio output from Audacity into them for decoding. It would also be helpful if the SatNOGS program had an API that allows direct downloading of audio files without clicking on the GUI. Maybe those features are already available – if so please note them in the Comments and we’ll add them to the blog.
There is a github project that uses the SatNOGS API to download audio, waterfall etc
https://github.com/deckbsd/glouton-satnogs-data-downloader