Tagged: Meteor-M2

A Complete Linux based Receiver and Decoder Application for Meteor M2




GLRPT User Interface Showing Processed Meteor M2 Images
GLRPT User Interface Showing Processed Meteor M2 Images

New GNU Radio Block for Decoding Meteor M2 Images

Thank you to Reiichiro Nakano for submitting news about his work on converting the Pascal based meteor_decoder software into a C++ GNU Radio block. meteor_decoder is a decoder for the Meteor M2 weather image satellite. Meteor M2 is a Russian weather satellite that transmits images down in the digital LRPT format. This provides much higher resolution images compared to the NOAA APT signals. With an RTL-SDR, appropriate satellite antenna and decoding software it is possible to receive these images.

Reiichiro works for Infostellar, which appears to be a Japanese company aiming to connect satellites to the internet via distributed and shared ground stations. It appears to be somewhat similar to the SatNOGs project. Reiichiro writes:

Just wanted to share a simple project I built for my company Infostellar, in the past week. I converted https://github.com/artlav/meteor_decoder to C++ and placed it within a GNURadio block for direct decoding of Meteor M2 images. It's a sink that expects soft QPSK demodulated signed bytes. Once the flowgraph stops running, it parses out received packets and dumps the received Meteor images in a specified location. 

The block is part of our Starcoder repository and can be installed from here (https://github.com/infostellarinc/starcoder/blob/master/gr-starcoder/lib/meteor_decoder_sink_impl.cc ).

A Lightweight Meteor M2 Demodulator

Over on GitHub dbdexter-dev has released a new lightweight and open source Meteor M2 demodulator. Meteor M2 is a Russian weather satellite that transmits images down in the digital LRPT format. This provides much higher resolution images compared to the NOAA APT signals. With an RTL-SDR, appropriate satellite antenna and decoding software it is possible to receive these images.

This new lightweight demodulator may be especially useful for single board PCs like the Raspberry Pi. Previously, on Linux GNU Radio based demodulators have been used, and GNU Radio isn't exactly a light weight piece of software. To use the software you first need to record an IQ file of the Meteor M2 LRPT signal, downsample the IQ file to 140 kHz (if required), then pass it into the demodulator. This will spit out an 8-bit soft-QPSK file which can be used with LRPTofflinedecoder (now known as M2_LRPT_Decoder) on Windows or meteor_decoder on Linux to generate an image.

An Example LRPT Image Received with an RTL-SDR from Meteor-2 M2.

Improving HRPT Reception + A Free HRPT Decoder

Back in December Tysonpower showed us  how he was able to receive HRPT weather satellite images with a 80cm and 1.2m satellite dish, LNA and Airspy Mini. 

If you didn't already know, HRPT signals are a little different to the more commonly received NOAA APT or Meteor M2 LRPT images which most readers may be more familiar with. HRPT images are more difficult to receive as they are broadcast in the L-band at about 1.7 GHz and so receiving them requires a dish antenna (or high gain Yagi antenna), L-band dish feed, LNA and a high bandwidth SDR such as an Airspy Mini. The result is a high resolution and uncompressed image with several more color channels compared to APT and LRPT images.

In the last video Tysonpower was successful with receiving HRPT images with his setup. But recently over on his YouTube channel and on his blog Tysonpower has shown how he has improved his HRPT reception by first optimizing the feed and adding in a copper matching line which helps improve the impedance matching of the feed. He also added an L-Band filter tuned to the HRPT signal which he notes made the biggest improvement, and he also moved all the components into a watertight box for permanent outdoor mounting. With these changes he's now able to consistently pull in some very nice imagery. All the images are still received by hand tracking the satellite dish as the satellite passes over, but he notes that he plans to experiment with motorized trackers in the future.

Note that the video shown below is narrated in German, but English subtitles are provided if you turn on YouTube captions.

[EN subs] HRPT - optimierungen und sehr gute Bilder

A sample HRPT image received by Tysonpower.
A sample HRPT image received by Tysonpower.

In addition to the above Tysonpower also writes that he has created a free HRPT decoder for the HRPT signals originating from NOAA satellites. He writes regarding HRPT decoders:

I found it quite complicated to find a decoder for HRPT when i started and there is still no one that you can just Download.

The only free Decoder is the gr-noaa example in gnu radio that has a depricated wx GUI and uses a input from a specific SDR. I used that gr-noaa example and created a decoder that uses the modern QT GUI and has a clean interface. You just put in a wav IQ file from SDR# for example and it will decode the Data into the file you entered. It is not the best one out there in form of signal processing, but a good start i would say.

The decoder can be downloaded from tynet.eu/hrpt-decoder. Below is a second YouTube video where Tysonpower explains how to use the decoder.

[EN subs] Kostenloser HRPT Decoder (GNU Radio) - Und wie man ihn nutzt

3D Printing a V-Dipole Bracket

Over on his YouTube channel user Tysonpower has uploaded a video that shows how to make a V-Dipole antenna. Back in March we posted about the V-Dipole which Adam 9A4QV first described. A V-Dipole is a simple antenna that normally consists of two metal rods, a terminal block and coax cable. It is particularly effective for reception of low Earth orbit satellites like the NOAA and Meteor M2 weather image satellites with an RTL-SDR or other similar SDR.

In his video Tysonpower shows how to build a slightly more rugged version using a 3D printed part instead of a terminal block. Aluminum welding rods are used for the elements. The 3D printed part ensures that the correct 120 degree ‘V’ angle is maintained and also provides a means for mounting the antenna to a pole. The 3D printing STL files are available on Thingiverse. Note that the video is in German, but English subtitles are available.

Note that we will also have a dipole antenna capable of being used as a V-Dipole available in our store in a few weeks time.

[EN subs] Bau einer V-Dipole Antenne – 3D Druck für mehr Genauigkeit und Stabilität

dopplerscript: Getting Doppler Updates from GPredict into GNU Radio

Thanks to Dave for submitting news of his recent release of his Python script called dopplerscript. This is a tool that can help people automate the reception and decoding of the Meteor M2 weather satellite in Linux with GNU Radio by providing a tool for automatic Doppler correction. He writes:

gr-gpredict-doppler is an out-of-tree gnuradio block for getting doppler updates from gpredict into a flowgraph. I’ve written a small python script (based on pyephem) that replaces gpredict for generating  the doppler updates. This script allows one to automate scripting the  reception of Meteor M2 satellite transmissions while compensating for the doppler shift.

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.

As low earth orbit satellites fly very quickly overhead, the signal will be affected by the doppler effect, thus shifting the frequency as it moves towards and away from you. Tools like this can be used to predict and compensate for this effect and thus providing better signal processing. Meteor M2 is a Russian weather satellite in low earth orbit which transmits digital LRPT weather satellite images that can be received with an RTL-SDR or other SDR.

An Example LRPT Image Received with an RTL-SDR from Meteor M2.

Real-Time decoding of Meteor-M2 on Linux

Recently RTL-SDR.com reader Mark wrote in and wanted to share his modified version of otti-soft’s GNU Radio flowgraph for decoding Meteor-M2 weather satellite images on Linux. The modified version allows for real time decoding, whereas the original version requires several offline decoding steps to be performed after recording the signal.

Mark writes:

I have modified one of otti-soft’s gnuradio flowgraphs so that they work with RTL-SDR and output the demodulated symbols to a TCP socket, from which the new version of LRPT Analizer (from robonuka.ru) can decode the data in real-time.

First, one needs to download and extract the AMIGOS version of the LRPT analyzer from robonuka.ru: ftp://meteor2soft:[email protected]/AMIGOS/AMIGOS2.zip.

(AFAIK, only the AMIGOS version is able to decode the data from a socket, which is required for real-time decoding).

The program is to be run under a 32-bit version of Wine.

When the satellite is overhead, open and run the flowgraph (attached) in gnuradio-companion and leave it running. You might need to adjust the gain.

Then, run the LRPToffLineDecoder.exe executable from the extracted archive.
It should display a constantly-updating constellation diagram. When the data is decoded, the channel images will start to appear in each section of the window.

That’s it, when the image is decoded, one can save it and close the windows of gnuradio-companion and the decoder.

Notes: when running the flowgraph, no other processes (rtl_sdr, rtl_power, gqrx, …) should use the SDR device.

The modified GRC file is available here.

The real-time Meteor M2 GNU Radio script for Linux
The real-time Meteor M2 GNU Radio script for Linux







Adam 9A4QV's V-Dipole for 137 MHz Weather Satellites.
Adam 9A4QV’s V-Dipole for 137 MHz Weather Satellites.


DIY 137 MHz WX sat V-dipole antenna
137 MHz NOAA WX sat reception using V-dipole antenna