Observation 1037954: Raw data Needed

Satellites & Observations Observations
12

It is very hacky, but involves the following steps:

  • Add a UDP sink to the gr-satnogs flowcharts connected directly to the osmocom source. Use 127.0.0.1 as the IP and 10*rigctl_port as the port.
  • Set the SATNOGS_PRE_OBSERVATION_SCRIPT environment variable to call a pre-observation script. Pass it the frequency, and possibly the script name. I use SATNOGS_PRE_OBSERVATION_SCRIPT="sh <path_to_script>/preobs_vhf.sh {{SCRIPT_NAME}} {{ID}} {{FREQ}}"
  • Create a pre-observation script that starts rffft reading from a fifo and nc listening to UDP packets from the specified port and dumping them into the fifo. My script is below.

My VHF (#39) and UHF (#40) stations run from the same x86_64 PC. Hence, I use 10*rigctl_port to differentiate between VHF and UHF recordings scripts, this to prevent both flowcharts sending UDP packets to the same port. The VHF and UHF satnogs-clients then have their own SATNOGS_PRE_OBSERVATION_SCRIPT and SATNOGS_RIG_PORT variables.

By using the UDP port, the gr-satnogs flowcharts can run even when starting nc or rffft failed, or are even turned off.

As you can see from the VHF pre-observation script, it only runs on the CW and AFSK flowcharts. I’ve also hardcoded the 1e6 sample rate, which is the gr-satnogs definition for an rtl-sdr. The -n 3600 option means only a single bin file is written by rffft, as the passes are usually shorter than 20 mins or so.

#!/usr/bin/bash
# Run strf
if [ "$1" = "satnogs_cw_decoder.py" ] || [ "$1" = "satnogs_afsk1200_ax25.py" ]; then
    freq=`echo $3 | awk '{printf("%d\n",$1-100000)}'`
    rffft -i <path_to_fifo> -p <output_path> -f $freq -s 1e6 -q -c 20 -n 3600 -F float &
    nc -l -p 45340 -u ><path_to_fifo> &
    echo "rffft and nc started"
fi
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