• scripts for sceduled lrpt reception and decoding

    tim.addison • 11/25/2017 at 20:36 • 3 comments

    I've been working on a ground station to receive LRPT images from the Russian meteor-m2 satellite for a while now.  The scripts for automated recording, decode, and uploading are working reliably now so I thought I'd share.

    All of this work is based on haslettj instructables guide, I modified his scripts to work with the tools below  to receive and decode LRPT signals. 

    Tools:

    In addition to the tools haslettj uses you'll need to get the following setup and working. Most are pretty self explanatory.

    Reception and QPSK decode

    I hacked up Otti's gnuRadio flow graphs to work from the command line for easier scheduling. There is a single input variable for the output file name. The output is a .s file which works with artlav's meteor_decoder tools.

    You'll want to change the rtl=xxx string on line 52 to work with your rtl device ID.

    This py needs gnuRadio 3.7 or newer installed, use your package manager.

    Image decode

    artlav's meteor_decode handles taking the captured qpsk data and turning it into a bitmap.

    Uploader

    i'm using prasmussen's gdrive tool to upload the decoded image to my google drive folder.

    Scheduler

    The github of my modified scripts is here.  Create a soft link to schedule_all so that it runs as a  cron task daily.  You'll need to modify each of the scripts to work with your own home directory location.  The qpsk decoder is dumping the received data into a file on a ramdisk. This is to lower latency and prevent gnuRadio from complaining about buffer overruns "OOOO".