RTL-SDR TUTORIAL: How to receive Meteor-M N2 LRPT Weather Satellite images in VHF with an RTL-SDR dongle.
Op 8 July 2014 werd een Soyuz 2-1B raket gelanceerd vanaf Site 31/6 van het Baikonur Cosmodrome in Kazachstan.
Met aan boord de Russische Weer Sateliet Meteor-M N2 (NORAD ID: 40069/Int'l Code: 2014-037A ).
10 July Re-entry Soyuz 2-1B Second stage over Australie:
Met uiteindelijk als doel een Leo orbit Period: 101.4 minutes / Perigee: 826.8 km / Apogee: 834.3 km / Inclination: 98.8 ° te bereiken.
Meteor-M2 is de 2de sateliet van de 4de generatie Russische weersat's, met de M-serie wil Rusland zijn LEO positie's weer hervatten voor operationele weervoorspellingen in real-time, Ozon laag, Radiatie,
Zeewater temperatuur en ijscondities in de polarie regio's.
De eerste Meteor-M1 sateliet was gelanceerd in 2009 om de structuur te testen alsmede de payload instrumenten.
Meteor-M1 was tot op heden 'functional but with limitations' door o.a. kalibratie problemen met IR, on-board geheugen problemen, LRPT kompressie errors.
Maar hij maakt nog sporadisch plaatjes -
http://planet.iitp.ru/english/spacecraft/meteor-m-n1_eng.htm
Meteor-M2-1 hydrometeorological satelliet staat voor 2015.
Meteor-M3 oceanographic satelliet voor 2020.
De Meteors zijn gebouwd door VNIIEM in Moskou elke satliet weegt 2,700 Kilogram inclusief 1,200 Kilogram multi-instrumenten/payload met een houdbaarheids datum van 5 jaar.
Meteor M2 heeft de volgende instrumenten aan boord:
MSU-MR Scanning Radiometer (1 km spatial resolution multichannel scanning unit, 6 channels, VIS/IR)
KMSS VIS Scanning Imager (6 channels implemented by 3 cameras, 50 m and 100 m spatial resolution)
MTVZA-GY Imaging/Sounding Microwave Radiometer (module for temperature and humidity sounding of the atmosphere, 26 channels, 10.6-183 GHz)
IRFS-2 Infrared FTS (Fourier Transform Spectrometer), an (IR atmospheric sounder, spectral range 5-15 µm, spectral resolution ~ 0.5 cm-1), also referred to as IKRS-2
GGAK-M Heliogeophysical Measurements Suite
Severjanin X-band Side-Looking Radar (500 m and 1000 m resolution)
DCS (Data Collection System)
RF LRIT / HRIT communicatie gedeelte:
X-band data transmission 8025-8400 MHz.
Transmitter output power 10 W
L-band data transmission 1.69 - 1.71 GHz (HRPT transmission)
Transmitter output power 5 W
Onboard data collection and transmission system from DCPs (Data Collection Platforms)
Data reception frequency from DCPs
401.2-402.0 MHz (UHF band)
VHF-band data transmission 137-138 MHz (MSU-MR bands in LRPT format)
Data transmission (LRPT transmission) Rate ½, k = 7 Convolution coded, I = G1, Q = G2, Power I:Q = 1:1, Symbol Rate 72 or 80 kilosymbols per second.
CCSDS Format. SCID 00, VCID 05, 3 out of APIDs 64 to 69, (MSU-MR channels 1 to 6) 72 kbps mode or 80 kbps Metop LRPT mode with UW Insertion.
Met name dat laatste kan erg intresant zijn voor huis tuin & keuken SDR gebruik omdat de NOAA APT satelieten (15/18 en 19) de laatste analoge zijn in hun soort en ook geen al te lang leven meer hebben (2016) totdat hun digitale opvolger dienst gaat doen.
Het digitale LRPT QPSK signaal van Meteor is te ontvangen op 137.100 (nu in gebruik) of 137.900 MHz een signaal lock komt ongeveer rond de 15-16dB.
Als Meteor met een Symbolrate van 72K uitzend (Internationale mode) is de data vrij te ontvangen.
Is deze 80K welke tijdens de test periode soms voorkomt, gebruiken ze een Unique Word insertion mode dwz dat het grond station alleen deze data kan ontvangen/coderen.
Omdat deze sateliet zich nog in de 'commissioning test phase' bevind gebeurd het wisselen van International mode 72K en 80K 'gecodeerd' heel onregelmatig en er worden soms ook, fill packets uitgezonden welke geen image data bevatten..
De Meteor sateliet moet vanaf het grondstation de commando's krijgen om van visual naar IR over te schakelen na het passeren van de terminator line (dag/nacht), dat loopt nog niet helemaal lekker dus avond's alleen zwarte beelden...
De gebruikte LRPT mode wijkt nogal af van de normale standaard LRPT mode dus werken de meeste software proccesing programma's niet.
Het door Noaa gebruikte Analog Automatic Picture Transmission (APT) signaal is dus niet compatible dwz wxtoimg software ect.
In Windows kunnen de beelden helaas (nog) niet in real-time worden verwekt zoals wxtoimg dat wel doet (GNU Radio ism een Linux distro kan dat wel al).
Er moet een Wave-IQ file worden opgenomen via SDRSharp die later verwerkt kan worden.
Het programma bestaat uit een aantal stappen welke doorlopen moeten worden en deze worden hieronder uitgelgt in het Engels door Raydel uit Cuba.
Provider Planeta kan alleen data ontvangen als Meteor binnen haar bereik komt (Moskou), en ze verheugen zich erg op beelden die zijn ontvangen van luisteraars over de hele wereld tijdens deze test periode!
Deze zijn te bewonderen bij de Meteor-M N2 LRPT Gallery op
http://meteor.robonuka.ru/ (Oleg's website).
Antenne:
Dito voor Noaa 137 MHz band een QFH of een crossed dipole/Turnstyle antenne is aanbevolen.
Een narrowband pre-amp voor 136-138 MHz als je die nog ergens hebt liggen zal het signaal nog een stukje versterken welke een groter beeld oplevert.
Meteor-M N2 volgen in windows:
Gpredict
http://sourceforge.net/pr...est/download?source=files of Orbitron als tracker kan je hier vinden -
http://www.stoff.pl
Heavensat - program for visual observing of artificial satellites.
Also available some additional tasks: passes prediction, calculation of satellites.
http://www.heavensat.ru/english/
Meteor-M N2 (NORAD ID: 40069) Tle file:
http://www.celestrak.com/NORAD/elements/weather.txt
Online trackers:
http://www.satview.org/?sat_id=40069U
http://www.n2yo.com/satellite/?s=40069
Planeta Operator -
http://planet.iitp.ru/english/index_eng.htm
Weather satellite status reports
http://homepage.ntlworld.com/phqfh1/status.htm
Meteor M2 Technical details:
https://directory.eoporta...ite-missions/m/meteor-m-2
http://www.spaceflight101...r-m-2-launch-updates.html
http://www.russianspaceweb.com/meteor_m2.html
A “Windows only” procedure (Offline decoding):
In order to view imagery, first we need to record a baseband I/Q WAVE file.
It is recommended to use a 0.900 MSPS sample rate at the RTL2832U dongle and maximum (192 KHz) for the Funcube Dongle (FCD), or something near 130 or 150 KHz if you use a different SDR.
You may use your favorite SDR program but I prefer SDRSharp (
http://sdrsharp.com/).
The satellite downlink frequency 137.100 or 137.900 has to be chosen as center frequency (137.100 MHz / 72K Symbolrate is currently in use).
It doesn’t matter what audio mode, volume or VFO frequency is chosen,
because we are recording base-band data centered on the main downlink there is no need neither to do Doppler tracking.
Always use “Correct IQ” and off-set tuning if available.
To improve constellation quality a lesser bandwidth is recommended if you are using an RTL.
In order to do it we can use the free audio handling software Audacity (
http://audacity.sourceforge.net/).
Open the recorded WAV file with it, and then at the left-bottom side change the sample rate to 130000 (130 KHz).
We can also remove and crop sections at the beginning and end of the recording where signal was low if required.
To save the file, proceed to the File menu, hit Export, select WAV as format, and save it.
We can then delete the original file to save space on hard disk (a 12 minute pass at 900 KHz sample rate takes more than 1GByte of space).
This step is not needed for the FCD, or other SDR with a sample rate lower than 200 KHz.
To process the WAV file we need to download this file:
https://www.dropbox.com/s/qq1fjyitpa3j14o/software.zip
Now we open LrptRx.exe (the other two programs are not needed*), load the new wav file (insome cases Swap I/Q should be selected, at least when recording with SDRSharp it has been always required).
We hit run and manually move the progress slider to the center where signal should be the best.
If we obtain a well defined 4 dots constellation, everything is OK, close the program, re-open it and process the entire file.
But if at the middle the constellation looks like an X or a square, try changing symbol rate from 72000 to 80000.
When the constellation is achieved with 4 dots, then the satellite is on 80K mode and therefore no decoding can be done with Paul’s programs.
It is important to know that when reached the end of the file LrptRx will run forever, unless we manually stop it, so keep an eye on the progress slider.
We can change the destination and name of the RAW file if desired; otherwise the program will save it on hard disk letter C:
To extract image from the RAW data we need Oleg’s decoder version 6 or higher and it can be found here:
http://meteor.robonuka.ru/soft/
Oleg’s program produces superb color images that can be saved in high resolution!
(Under some conditions it may be a good idea to check the “Ignore RS fatal error” option).
Then hit 72K or 80K button depending of the received symbol rate.
Browse for the RAW file and open.
If you don’t find the file, you can select “All (*.*)” in the file type filter.
Now the program will begin to process the file.
After finish the processing, you can click on the “Generate RGB” button to see the result.
In the new window hit “Save” to keep the image, it will be stored in the same folder that contains the raw file.
*Paul’s software was made for Meteor-M N1 (not active) which has different image structure than N2 so several image artifacts like two black rows, and others are visible when used to decode N2 imagery, but some pictures can be obtained.
But the programs were designed for experimental and learning purposes so there is no method to save the image or see it entire in full resolution.
Also it is only compatible with the 72K mode, so the 80K mode cannot be decoded.
However, this process can be slow and take some time because there are multiple steps.
First record the entire pass into a WAV file (10 to 15 minutes).
Second, re-sample if using an RTL (7 minutes, or not needed if using less than 200 KHz bandwidth).
Third, extract symbols, which take around half the length of WAV file (usually 7 minutes).
And finally process imagery (up to 5 minutes).
If you want to remove some steps and proceed direct to real-time reception and store symbol data you can use a simple Linux based receiving program.
The process takes much less time because steps of recording, re-sampling and symbol extraction are done at the same time during the satellite pass.
A “Linux/Windows” procedure (fast):
First we need a Linux version that already has all the required libraries pre-installed:
http://downloads.gnuradio.org/releases/gnuradio/iso/
After downloading the ISO file we need to install it into a 4GB or bigger flash drive with this program:
http://www.pendrivelinux....-installer-easy-as-1-2-3/
It is recommended to add a persistence file to store and save the changes; otherwise the configurations will be lost every time we boot.
Calculate the size of the file depending of your flash drive capacity and the fact that Linux will take at least 2.5GB.
Then copy the .PY files contained on this ZIP to your hard drive or a different flash drive.
https://www.dropbox.com/s/par34n42m1r68k3/meteor_rx.zip
Connect the Linux flash, and reboot computer, command your PC to boot from the USB and wait for Ubuntu to load.
It will said after booting that some error was detected, just click cancel and proceed to the indicated steps in the readme.txt file found inside the meteor_rx.ZIP
After running the app you should see a spectrum in the window showing data, if no signal or spectrum is shown, probably the RTL or FCD was not recognized.
The programs are my own edited version from a script written originally by Martin Blaho, I changed some parameters and things to adapt it to my station conditions, so in case of
problems it is my fault, but I guess that it should run equally good in other stations.
Unfortunatelly some users have reports that the Linux script for FunCubeDongle (FCD) doesn't work.
Main concern is regarding the frequency correction ppm value of each RTL dongle and proper gain value for FCD, so probably in other people computer, the downlink frequency can by 5 to 10
KHz up or down the nominal, or a different gain should be needed.
When the signal to noise ratio in the spectrum from Meteor satellite transmission is above 5dB, go the second panel and look at the constellation.
If it looks like a circle, increase PLL alpha, as soon as it is formed by four dots (even if spread), reduce the PLL alpha until reach value “1m”, if you suddenly lose lock and it become a circle again then increase it, but always try to keep it as low as possible. There is no need to change Clock alpha. Keep receiving until the end of the pass, and then close the program.
The soft-decision symbol file and a WAV file (only needed for debugging and testing purposes) are saved in Linux desktop.
To be able to open the file, we have to copy the .s file to our hard disk or second flash drive, and then we can re-start the computer without Linux flash and open Oleg’s program decoder to extract the images and build the color composite.
In the first icon at the top left section we can search other installed Linux programs.
You can look for “gpredict” which is a satellite tracker, after downloading a fresh set of keplers and updating our coordinates and adding Meteor-M N2 satellite to the list we will be able to see the time of satellite pass as well as its current position.
All of these steps will be lost if we didn’t created a persistence file.
Note The Meteor satellite has 3 visual channels and 3 IR channels, but LRPT only supports 3 channels each time.
The satellite has to be commanded to change from visual to IR after passing the terminator line (day/night), but at the moment only black images are during night.
But in a very very clear cloud free evening you can take the black picture and open it with an image editor program to change bright/contrast and with a lot of luck you may be able to see some brighter points from the city lights!!!
Thanks and credit fly out to Raydel Abreu Espinet CM2ESP (Guide), Oleg (LRPToffLineDecoder), Martin Blaho (Linux Scripts), Paul from Australia (LrptRx) and all the helpfull people of Weather Satellite/Discussion Group!
Veel plezier met testen
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Voor 57% gewijzigd door
WC-Juf op 05-09-2014 02:03
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