Category: Satellite

January 19, 2015

Airspy GNU Radio Script for Receiving LRPT Meteor-M2 Weather Satellite Images

Previously we posted about receiving LRPT weather satellite images from the Russian Meteor-M2 weather satellite using the RTL-SDR. Now on GitHub, developer otti-soft has uploaded a LRPT decoder GNU Radio script for the Airspy. The script appears to be a modified version of the GNU Radio based real time decoder for the RTL-SDR, but optimized for the Airpsy and it’s 10 MSPS or 2.5 MSPS sampling rates. Note that although this is a real time receiver, the final image still needs to be processed on a Windows PC using LRPToffLineDecoder.

Also over on Twitter otti-soft has been uploading some images that he has received with his Airspy.

Real time LRPT Receiver for the Airspt — Real time LRPT Receiver for the Airspy

December 30, 2014

Chaos Communications Congress Talks – Iridium Pager Hacking

A few days ago the Chaos Communications Congress (a technology and hacking focused conference) commenced. Among the talks there was one about reverse engineering the Iridium satellite paging system using software defined radio. Iridium satellites provide global communications via special satellite phones, pagers and other transceivers.

In the talk the speaker shows how they used a USRP radio together with a cheap active iridium antenna, a bandpass filter and an LNA to receive the Iridium satellite signals. They also mention that an E4000 RTL-SDR together with an LNA and appropriate home made antenna for frequencies in the ~1.6 GHz region can also be sufficient. Once they were able to receive signals they were then able to reverse engineer the signal and create several pieces of software to decode the pager messages. The code is available on their GitHub at https://github.com/muccc/iridium-toolkit.

Sec, schneider: Iridium Pager Hacking

Watch this video on YouTube

December 23, 2014

Listening to SSTV from the ISS with an RTL-SDR

On December 18 and 20 the International Space Station transmitted several SSTV images to celebrate what would have been the 80th birthday of Yuri Gagarin who was the first human to orbit the Earth. SSTV stands for Slow Scan Television and is a method for sending small low resolution images over radio.

Over on YouTube several RTL-SDR users captured these images. UltraTechie shows a video where he captures the SSTV image using a portable set up consisting of a Windows 8 tablet running SDR#. He used a handheld 3 element 2m Yagi antenna to tune into the 145.8 MHz signal. UltraTechie writes that he also used an LNA, but that it was probably not required as the signal was quite strong.

ISS SSTV reception on a portable setup using RTL-SDR

Watch this video on YouTube

Another YouTube user Tom Mladenov shows another video where the SSTV image is received. Tom used a QFH antenna.

Watch this video on YouTube

November 13, 2014

SatNOGS – Hackaday Prize Winner uses RTL-SDR in Design

The popular Hackaday blog recently announced the winner of their grand competition to win a trip to space or $200k. The goal of the competition was to design and build the best example of “an open, connected device”. The winner of the competition is SatNOGS, a system that hopes to enable a low cost network of satellite ground stations thus enabling greater access to satellite data. The radio receiver used in the SatNOGS hardware is a standard RTL2832U R820T RTL-SDR dongle.

The SatNOGS hardware is a system that uses high gain antennas, tracking motors, a RTL-SDR and a PC running GNU Radio and other software to automatically track, receive and record satellites as they pass over head. The open source software works to automatically schedule observations and record them to an online database.

More information about SatNOGS can also be found on their website https://satnogs.org/.

The third prize winner of the Hackaday prize was the ‘PortableSDR’, which we posted about previously.

SatNOGS Hardware with RTL-SDR Dongle Visible

SatNOGS Project - THP Finals

Watch this video on YouTube

November 12, 2014

Decoding the Russian Parus (Cosmos) Navigation Satellites with the RTL-SDR

Once again Happysat, who previously wrote in to RTL-SDR.com to let us know how to receive dead satellites with the RTL-SDR has again written in to let us know about his latest achievements.

Happysat has recently been using a RTL-SDR to decode the discontinued Russian Parus (Cosmos) Navigation Satellites. These are low earth orbit satellites operated by the Russian Space Forces that are used for military communication and navigation. Since 1974 there have been 99 Parus satellites launched, but there are only three currently active.

With an RTL-SDR, SDR# and decoder software, Happysat was able to decode data from the satellite which includes the current Moscow time and various location and telemetry data.

Russian Parus (Cosmos) Satellite Decoded Data

Happysat writes:

The Russian Military Parus satellites are/where used for low-earth orbiting navigation information and store-dump radio communications relay service for Red Navy surface vessels and submarines.

Each satellite is in a near-circular orbit of about 1000 km (620 miles).The orbits are polar (pass over the poles of the earth) and stay stationary in space so that as the earth rotates, the satellite covers different parts of the planet.

There are three currently operational, Cosmos 2407, 2414, and the last one launched in this series (April 2012) Cosmos 2463 with a lifespan of 4 years.

They are discontinued now as the GLONASS Navigation systems did take over the service which are providing a better accurate GPS position.

Why the Parus-Satellites are currently still broadcasting data is unknown. Most probably due the older vessels and submarines are still using Shkhuna Radio systems.

The satellites transmit two radio carriers, one on VHF which is FM modulated with the navigational data around 10 watts, and one on UHF which is unmodulated (tracking Beacon).

Already in 1980 the British Kettering Group was able to decode the encryption. The first 18 Bit of data contain the Moscow time, the other Bits contain the positions and orbits from the other active Parus-Satellites. Very similar data like our GPS output and the Orbcomm satellites (on 137 Mhz) with OrbcommPlotter (explained also on rtl-sdr).

With RTL-SDR and SDRSharp its possible also to decode the Russian Military Parus satellites.

Alan Cordwell did write a Java decoder that will decode the navigation data from the VHF transmission in non-real time. cosmos_export.rar [Mirror] It is experimental software and very basic.

Unfortunately his website is offline but still on web-archive (link to web archive)

You will need to record the audio from the satellite and save it as a 44100, 8-bit, mono .wav file. Which means SDRSharp included wave recording is not suitable to do this you need a external program like Audacity or any favourite which can handle the requirements above.

Then you will need to apply narrow bandpass filtering to it at 3, 5 and 7 kHz. Without this filtering step only a small portion of the data will be available, i’m still struggling with this step 😉

He did use Cool Edit Pro to do this, there are no doubt other apps available like Audacity. Included is a sample filtered audio file for you to try it with, it’s in the rar archive as well.

Unpack the archive to a convenient location a folder called cosmos-export will result. Execute the file cosdec.jar to run the application. Open a file with file/open and in the file chooser dialog select the wav file. To decode it go to Actions/Process File.

To write all output to a log file: check the Dump to log option in File menu (log file will be created with same name as audio file but with .log extension appended). Datascope does as it suggests; it launches a little frame that shows (using graphics) the waveform of the data recovered from the audio. The frequency axis is upside down! you’ll see the 3, 5 and 7kHz bits with 7 at the bottom.

There is another program (Sorcerer) which can decode in real-time only, the current actual atom Moscow time from the satellites.

[sorcer download]

Start sorcerer and go to the menu add decoder on the left FSK and choose COSMOS NAVDATA. Move the first bar slider in the spectrum to 3 kHz so the second and third are on 5 and 7 KHz as seen in the screenshot.

Its possible to run this application and record audio at the same time which is later on needed for the cosmos_export Java program.

The frequencies are as follows:

Cosmos 2407 and 2414
VHF Frequency NavData 149.970 MHz, Tracking Beacon 399.920MHz

Cosmos 2463
VHF Frequency NavData 149.940 MHz Tracking Beacon 399.840MHz

Orbital parameters and predictions:

You need to run Orbitron in SDRSharp to take care of the Doppler!

TLE’s for the current satellites, (these are current as of 10th November 2014)

COSMOS 2407
1 28380U 04028A 14313.17698750 .00000073 00000-0 59418-4 0 2927
2 28380 82.9601 332.2565 0038129 220.5020 139.3308 13.75978622517201

COSMOS 2414
1 28521U 05002A 14314.08629907 .00000094 00000-0 65641-4 0 6502
2 28521 82.9510 6.9860 0040501 164.6577 195.5838 13.87513505496523

COSMOS 2463
1 36519U 10017A 14313.57202739 -.00000009 00000-0 -27079-4 0 4041
2 36519 82.9553 122.2841 0036820 7.8477 352.3245 13.71357663227175

New ones can be downloaded at celestrak: musson.txt

Good luck and if anyone has good knowledge on how to apply narrow bandpass filtering at 3, 5 and 7 kHz, please write in the comments!

Note that Orbitron can be downloaded from http://www.stoff.pl/, and the SDR# plugin to interface with it can be downloaded from SatelliteTracker2.zip or here. A tutorial on using Orbitron with SDR# for Doppler correction can be found on our NOAA Weather satellite reception tutorial.

SDR# with Orbitron for Doppler Correction and Sorcerer for Decoding Cosmos

October 31, 2014

Receiving Dead Satellites with the RTL-SDR

Recently happysat, a reader of RTL-SDR.com wrote in to let us know about an unusual hobby he has found with the RTL-SDR. Happysat has been using the RTL-SDR together with a QFH antenna to detect old decommissioned satellites in the 136-138 MHz and 150-400 MHz frequency ranges. Although these satellite’s batteries have long been expired, because of some sort of chemical reaction due to thousands of failed recharge cycles the batteries begin to conduct over time and allow the satellite to be powered directly from the solar panels thus activating the transmitter. Happysat writes:

During weathersat reception of NOAA/Meteor on the 137 MHz band i did see quite often unidentified interrupting signals. After a bit of Googling around I learned that these were Dead Satellite’s that still are broadcasting given the right sunlight conditions, the signal strength is sufficient to show up in SDRSharp, not all signals are very strong some very weak and needed a good close up zoom in SDRSharp. There are many shutdown Satellite’s who apparently having a life of their own varying from Military, Navigation, Experimental, Weather, and also Amateur ones. Most are not transmitting any usable telemetry or weather images but they still use the original frequencies to sent out a unmodulated carrier, which interferes with the current operational Satellite’s in the 136/138 MHz band. Normally when a satellite goes out of service and runs almost out of fuel the last reserve is used to shift it in a graveyard orbit which resides above the normal operation orbit, it will be switched off and left on their own. But this will not always goes as planned, sometimes due solar radiation or other technical failures it will not respond again to the ground station commands, which leaves the Satellite in its current orbit. Some have a timer onboard which will be activated at end of life scheduled to end/shortcut the power feed to the transmitter so it will not broadcast again, also this can fail. Until some day they might not work at all anymore.. But that can take a while one of the oldest satellite still broadcasting are: Transit 5B-5 (Military Navigation) from 1964 – they can be heard in either CW or USB mode. An audio example of Transit is over here [link to example] (my recording – link to online stream uploaded by commenter Jordan here) it sounds like some kind of melody song. And LES-1 from 1965 (Lincoln Experimental Satellite 1) – Audio example over here [link to example] thanks to Phil Williams. Others are just a spooky hauling sound like LES-1, NOAA’s etc due the Voltage fluctuation from the solar panels. DD1US does have a very nice collection images and orginal sounds on : [space sounds] A list of frequencies and more in depth details can be found on Mike Kenny’s excellent website: [mike kenny’s website] My TLE containing all current Deadsatellite’s is available on dropbox for anyone would like to try out – [TLE file] Updated once a week. You can use it in your favorite tracker, i prefer Gpredict for this course of the unstable frequency and Doppler effects Orbitron will not always suite on this birds.

Happysat has also provided a frequency database for SDR# containing the frequencies of all the dead satellites.

October 13, 2014

Tutorial Video Showing How to Receive Meteor M2 Weather Satellite Images with the RTL-SDR

Recently we posted about a tutorial showing how to receive LRPT weather satellite images from the new Russian Meteor M2 satellite. Now over on YouTube user Tom Mladenov has uploaded a tutorial video showing all the tutorial steps.

The reception process is to essentially record an IQ file of an LRPT transmission using SDR#, reduce the sample rate of the IQ file using audacity and then decode the file using LRPTrx.exe. Then finally the decoded data can be imported into LRPTofflineDecoder to produce an image.

Watch this video on YouTube

September 6, 2014

RTL-SDR Tutorial: Receiving Meteor-M N2 LRPT Weather Satellite Images with an RTL-SDR

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Update 29 June 2023

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With the launch of Meteor M2-3, the loss of all prior Meteor M satellites and the release of new software, this tutorial is now outdated. We will eventually update this tutorial, but for now we will reference this post which has a brief high level overview of how to receive and decode images from the Meteor M2-3.

The current best tutorial for receiving Meteor M2-3 is available from Happysat at https://github.com/happysat/Setup-Meteor-M-N2-3-with-LRPT-Decoder-and-MeteorGIS/blob/main/README.md

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Update 02 August 2019: Please use Happysats tutorial which is available here. Happysats tutorial will work for Meteor M-N2-1 and Meteor M-N2-2.

Update 11 May 2015: There is now a real time method for decoding Meteor-M2 LRPT images. Please also check out the new tutorial available here.

The Meteor-M N2 is a polar orbiting Russian weather satellite that was launched on July 8, 2014. Its main missions are weather forecasting, climate change monitoring, sea water monitoring/forecasting and space weather analysis/prediction.

The satellite is currently active with a Low Resolution Picture Transmission (LRPT) signal which broadcasts live weather satellite images, similar to the APT images produced by the NOAA satellites. LRPT images are however much better as they are transmitted as a digital signal with an image resolution 12 times greater than the aging analog NOAA APT signals. Some example Meteor weather images can be found on this page and the satellite can be tracked in Orbitron or online.

The RTL-SDR and other SDRs like the Funcube along with some free software can be used to receive and decode these images. LRPT images from the Meteor-M N2 are transmitted at around 137.925 MHz, so any satellite antenna like those commonly used with the NOAA weather satellites can be used.

NOTE: Meteor M1 ~~has come alive~~, (now offline again), ~~so the frequency of Meteor M2 was changed from 137.1 MHz to 137.9 MHz.~~ ~~Meteor M1 is now at 137.1 MHz and can be received using the same steps as in this tutorial, though please note that images from Meteor M1 are not perfect since the satellite is tumbling.~~

Happysat, a satellite monitoring enthusiast has emailed us with a comprehensive tutorial showing how the RTL-SDR can be used to receive and decode these LRPT images (pdf warning) (txt file). The procedure is not quite as simple as with the NOAA satellites as it involves first pre-recording the transmission as a baseband I/Q file in SDR#, changing the sample rate in Audacity, processing the file with the Lrptrx.exe software, and then using Oleg's LRPToffLineDecoder (now called M2_LRPT_Decoder) to finally produce the image (in case the link is down for LRPToffLineDecoder/M2_LRPT_Decoder), try mirror here or here).

The tutorial also shows an alternative and faster Linux based method using some GNU Radio scripts, but with the final processing still done with Oleg's decoder in Windows.

The tutorial can be downloaded in PDF form from this link or alternatively in a text file here.

Update: This newer post now shows a slightly faster way for receiving and decoding LRPT images on a Windows PC which does not require the use of Audacity.