dopplerscript is a command-line tool to input satellite doppler shifts into a gnuradio flowgraph. The doppler.py script replaces gpredict as the source for doppler frequency updates in gr-gpredict-doppler, making it easy to script satellite reception.

Requirements: gr-gpredict-doppler, pyephem

I have also included a command-line flowgraph based on the classic one by otti-soft which will receive Meteor M2 LRPT transmissions. This version of the flowgraph includes the gr-gpredict-doppler modifications required to use the doppler updates from doppler.py (or gpredict).

Usage: I usually run the rtlsdr_doppler_m2_lrpt_rx_nogui.py script using timeout as follows:

 timeout <satpass_duration> rtlsdr_doppler_m2_lrpt_rx_nogui.py <filename> <pll_alpha>

e.g.

 timeout 932 rtlsdr_doppler_m2_lrpt_rx_nogui.py meteor_20170831_1632 .012

where 932 is the duration of the satellite pass, meteor_20170831_1632 is the filename prefix for the soft symbol file, and 0.012 is the loop bandwidth of the Costas Loop in the flowgraph. Once the flowgraph is running, I start the doppler.py script by running:

 doppler.py

The doppler.py script will automatically close when the flowgraph is terminated.

You should also be sure to change your location data and the pointer to the satellite TLE data in the doppler.py file.