Howto: Meteor M2 weather satellite image decoding

PE0SAT · July 3, 2023, 4:59am

You can enable the IQ file creation via sudo satnogs-setup and then the option advanced -> radio

There are two options that influence the behavior:

ENABLE_IQ_DUMP
Type
boolean

Default
False

Required
No

Description
Create I/Q data dumps for every observation. Use this feature with caution. Enabling this setting will store large amount of data on the file-system.

IQ_DUMP_FILENAME
Type
path

Default
None

Required
No

Description
Path to file for storing I/Q data dumps.

The files created are pretty big and if you use a Pi the writing of these files can wearout your SD card.

n5zkk · July 3, 2023, 5:18am

Thanks for the quick reply. On the last pass I did have these settings. SatNOGS Network - Observation 7804770

ENABLE_IQ_DUMP=“1”
IQ_DUMP_FILENAME=“/tmp/iq_vhf.raw”

After the pass I tried changing the name to iq.dat and then running the postob.sh with no luck.

#!/bin/bash
echo "POST OBSERVATION SCRIPT RUNNING"

#ID="$1"
ID="satnogs_7804770_2023-07-03T03-59-00"
DATE="$2"

demod=/usr/local/bin/meteor_demod
decode=/usr/local/bin/meteor_decode

cp /tmp/iq.dat /tmp/${ID}.dat

${demod} --batch --quiet -O 8 -f 128 -s 144000 -m oqpsk --bps 16 /tmp/${ID}.dat --stdout | \
${decode} --batch --quiet --diff -a 65,65,64 -o /tmp/.satnogs/data/data_${ID}_${DATE}.png -

rm -f /tmp/${ID}.dat

#old method
#python /home/pi/satnogs-extras/scripts/process_meteor.py  "$1" "$2" "$3" "$4"

echo "POST OBSERVATION SCRIPT FINISHED"


SATNOGS_SOAPY_RX_DEVICE="driver=rtlsdr"
SATNOGS_RX_SAMP_RATE="2.048e6"
SATNOGS_ANTENNA="RX"
UDP_DUMP_HOST="127.0.0.1"

SATNOGS_RF_GAIN="8.7"
#SATNOGS_RF_GAIN="32.8"
#SATNOGS_RF_GAIN="16.6"
SATNOGS_GAIN_MODE="Overall"

# Black Nooelec SDR
# 0.0 0.9 1.4 2.7 3.7 7.7 8.7 12.5 14.4 15.7 16.6 19.7 20.7 22.9 25.4 28.0 29.7 32.8 33.8 36.4 37.2 38.6 40.2 42.1 43.4 43.9 44.5 48.0 49.6
# Silver Nooelec SDR
# -1.0 1.5 4.0 6.5 9.0 11.5 14.0 16.5 19.0 21.5 24.0 29.0 34.0 42.0


ENABLE_IQ_DUMP="1"
IQ_DUMP_FILENAME="/tmp/iq_vhf.raw"


###Control the PSTROTATOR with this stuff
SATNOGS_ROT_MODEL="ROT_MODEL_NETROTCTL"
SATNOGS_ROT_BAUD="0"
SATNOGS_ROT_PORT="192.168.14.144:4533"

SATNOGS_PRE_OBSERVATION_SCRIPT="satnogs-pre {{ID}} {{FREQ}} {{TLE}} {{TIMESTAMP}} {{BAUD}} {{SCRIPT_NAME}}"
SATNOGS_POST_OBSERVATION_SCRIPT="/home/pi/postob.sh --id {{ID}} --tle{{TLE}}"

PE0SAT · July 3, 2023, 5:30am

What information or error messages did you get?

Are the meteor_demod and meteor_decode build via github ?

n5zkk · July 3, 2023, 5:36am

Yes the meteor_demod and meteor_decode were just built from the github source today.

After the meteor_demod finished it had 00:00:00 for the time and no files generated. I will give it another try after the next good pass. Thanks again.

PE0SAT · July 3, 2023, 5:45am

Not the best reception but this was producing an image.

Unzip the file and use it as input.

bcsak · July 3, 2023, 6:51am

You need to set -s 128000 instead of -s 144000. But if you have individual saved I/Q files, try first to run manually on these dumps, then add the post-obs script if all works fine

n5zkk · July 3, 2023, 2:37pm

It looks like the VIT never drops below 1300 during the decode. I have a couple of METEOR M2-3 METEOR 2 2-3 METEOR-M N2-3 (whatever it is called) daylight passes coming and will try some more settings.

n5zkk · July 3, 2023, 10:11pm

I had a good daytime pass over EM00 and have been playing around with the IQ file.
https://network.satnogs.org/observations/7805833/

So far I have found this to work but the $ID and $DATE were not coming over so the png file did not upload to the observation.

#!/bin/bash
echo "POST OBSERVATION SCRIPT RUNNING" 
ID="$1"
DATE="$2"
demod=/usr/local/bin/meteor_demod
decode=/usr/local/bin/meteor_decode

${demod} --batch --quiet  -s 144000 -m oqpsk  /tmp/iq.dat --stdout | \
${decode} --batch --quiet --diff  -o /tmp/.satnogs/data/data_${ID}_${DATE}.png -

#rm -f /tmp/iq.dat

echo "POST OBSERVATION SCRIPT FINISHED"

n5zkk · July 4, 2023, 4:15am

Thanks for the help everyone that contributed to the thread. I have finished the work to automate the METEOR M2 2-3 observations and then upload the results including the decoded graphic.

https://network.satnogs.org/observations/7805833/

For the satnogs-client configuration I change the client file by hand and here is the code that I am using. SatNOGs version 1.8.1
sudo nano /etc/default/satnogs-client

SATNOGS_API_TOKEN="xxxx....."
SATNOGS_DB_API_TOKEN="xxxx....."

SATNOGS_STATION_ID="xxxx"
SATNOGS_STATION_LAT="30xx"
SATNOGS_STATION_LON="-99xx"
SATNOGS_STATION_ELEV="500"

SATNOGS_SOAPY_RX_DEVICE="driver=rtlsdr"
SATNOGS_RX_SAMP_RATE="2.048e6"
SATNOGS_ANTENNA="RX"
UDP_DUMP_HOST="127.0.0.1"

SATNOGS_RF_GAIN="8.7"
#SATNOGS_RF_GAIN="32.8"
#SATNOGS_RF_GAIN="16.6"
SATNOGS_GAIN_MODE="Overall"

# Black Nooelec SDR
# 0.0 0.9 1.4 2.7 3.7 7.7 8.7 12.5 14.4 15.7 16.6 19.7 20.7 22.9 25.4 28.0 29.7 32.8 33.8 36.4 37.2 38.6 40.2 42.1 43.4 43.9 44.5 48.0 49.6
# Silver Nooelec SDR
# -1.0 1.5 4.0 6.5 9.0 11.5 14.0 16.5 19.0 21.5 24.0 29.0 34.0 42.0

#METEOR The IQ file is huge so it goes to an external drive with satnogs:satnogs ownership
ENABLE_IQ_DUMP="1"
IQ_DUMP_FILENAME="/media/usb/satnogs/iq.dat"

###Control the PSTROTATOR with this stuff
SATNOGS_ROT_MODEL="ROT_MODEL_NETROTCTL"
SATNOGS_ROT_BAUD="0"
SATNOGS_ROT_PORT="192.168.14.144:4533"

SATNOGS_PRE_OBSERVATION_SCRIPT="satnogs-pre {{ID}} {{FREQ}} {{TLE}} {{TIMESTAMP}} {{BAUD}} {{SCRIPT_NAME}}"
#METEOR Run this script after the observation
SATNOGS_POST_OBSERVATION_SCRIPT="/home/pi/postob.sh {{ID}} {{TIMESTAMP}}"

The post observation script postob.sh
Again I am storing the IQ file on an external drive to avoid wearing out the Raspberry Pi SD Card

#!/bin/bash
echo "POST OBSERVATION SCRIPT RUNNING"

ID="$1"
DATE="$2"

demod=/usr/local/bin/meteor_demod
decode=/usr/local/bin/meteor_decode

${demod} --batch --quiet  -s 144000 -m oqpsk  /media/usb/satnogs/iq.dat --stdout | \
${decode} --batch --quiet --diff  -o /tmp/.satnogs/data/data_${ID}_${DATE}.png -

#rm -f /tmp/${ID}.dat

echo "POST OBSERVATION SCRIPT FINISHED"

bcsak · July 4, 2023, 9:28am

Again I am storing the IQ file on an external drive to avoid wearing out the Raspberry Pi SD Card

If you have sufficient amount of RAM, you can also store these I/Qs in /dev/shm. Those (i mean, I/Qs) can be rather big, 1/2 gigabytes or so, so check it in advance.

bcsak · July 6, 2023, 9:33am

So, if we do an FSK 32000 recording, just change the above -s 144000 to -s 128000. And then all will work automatically: SatNOGS Network - Observation 7823743. It seems that now Meteor M2-3 is transmitting the 72ksps OQPSK images at 137.1MHz and not at 137.9MHz.

PE0SAT · July 6, 2023, 10:31am

@bcsak, yes the FSK32000 IQ recordings can be used and I am successful as can be seen by looking at this observation SatNOGS Network - Observation 7803282

I haven’t fully automated the demod → decode → upload yet.

Here is the script that I use for now.

#!/usr/bin/env bash
#
# Upload to the network:
#
#  ${SATNOGS_OUTPUT_PATH}/data_<obsid>_YYYY-MM-DDTHH-MM-SS.png

if [ -z "${1}" ]; then
	echo "Input variable missing."
	echo "Syntax: $0 input file sample rate (default 128e3)"
	exit 1
fi

SPS="${2:-128000}"

echo "Decode ${1} at a ${SPS} sample rate"

meteor_demod -O 8 -f 128 --batch --quiet --bps 16 -s "${SPS}" \
	--mode oqpsk "${1}" --stdout - | \
meteor_decode -o "${1}".png --diff -a 65,65,64 -

n5zkk · July 9, 2023, 11:18pm

I changed to using the 137.1 IQ Transmitter and had to change to 128000 for the demod. Also did the post processing with SmoothMeteor Smooth Meteor. Much better that my earlier results.
SatNOGS Network - Observation 7829917

SA2KNG · July 10, 2023, 11:20am

I’m working on the UDP method in my docker addons repo: meteor.sh
Short documentation in the README.md

bcsak · July 11, 2023, 7:39am

Can you change the FSK 32000 mode to FSK 36000? Then, the I/Qs would be exactly the same for LPRT and these modes… just to minimize the post-processing issues even this alternation between 137.1 and 137.9 makes trouble…

Another idea: can we add a mode of FSK 288000, centered at 137.5? In this case, a post-processing script can try to make a +/- 400kHz correction and decimation of 8 to 144000ksps after, and then trying to decode both channels…

SA2KNG · July 11, 2023, 12:58pm

Good idea, Jan changed them both just now.

@cgbsat had a similar suggestion, it will be a bit demanding and possibly lock up some stations, not sure if this is better rather than doing a few obs on either frequency. for investigation we can just split a pass in two and do two different obs.

If we are talking custom flowgraphs etc, we still want the metadata of the obs to match what we are producing as data (images, waterfall, frames). otherwise it will get messy very fast and the obs frequency doesn’t match what data is produced.

geoscan · July 12, 2023, 11:31am

Does anybody have FSK 36000 IQ recording of Meteor that producing an image? I wasn’t able to make it work on my station

SA2KNG · July 12, 2023, 4:07pm

I can report that my automation works now, check out the previously linked repo.
This is the first obs that produced image, weak reception so not so many lines: MPDUs received: 1142 (456 lines)
The issue I missed at first was the floats that comes over udp needs to be converted to ints for the demod (this could be added to meteor_demod at some point).

PE0SAT · July 16, 2023, 12:46pm

Frequencies and symbol rates are changed.

An updated script around the tools meteor_demod and meteor_decod found at dbdexter-dev (Davide Belloli) · GitHub

#!/usr/bin/env bash
#
# Input file example: iq_144000_7872624.raw
#
# File name to upload to the network:
#  ${SATNOGS_OUTPUT_PATH}/data_<obsid>_YYYY-MM-DDTHH-MM-SS.png

OBS=${1}
SPS=$(echo ${OBS%.raw} | awk -F'[_]' '{print $2}')
OBSID=$(echo ${OBS%.raw} | awk -F'[_]' '{print $3}')
UTIME=$(date -u +'%FT%T')
SYMB="${2:-80000}"

if [ -z "${1}" ] || [ -z "${SPS}" ]; then
	echo "Input file is missing."
	echo "Syntax: $0 input file."
	exit 1
fi

echo "Decode ${OBS} ${SYMB} symbol rate at a ${SPS} sample rate"

case ${SYMB} in
  72000)
    meteor_demod -O 8 -f 128 -r 72000 --batch --quiet --bps 16 -s "${SPS}" \
	--mode oqpsk "${1}" --stdout - | \
    meteor_decode -o "data_${OBSID}_${UTIME}".png --diff -a 65,65,64 -
    ;;

  80000)
    meteor_demod -O 8 -f 128 -r 80000 --batch --quiet --bps 16 -s "${SPS}" \
	--mode oqpsk "${1}" --stdout - | \
    meteor_decode -o "data_${OBSID}_${UTIME}".png --int --diff -a 65,65,64 -
    ;;

  *)
    echo "Syntax: ${0} input file symbol rate."
    ;;

esac

PE0SAT · July 16, 2023, 2:24pm

The M 2-3 LRPT IQ recording transmitters are changed 40k, this will produce a 160000 sample rate IQ recording.