Howto: Meteor M2 weather satellite image decoding

SatNOGS Software
122

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

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 channelsā€¦

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123

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 doesnā€™t match what data is produced.

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124

Does anybody have FSK 36000 IQ recording of Meteor that producing an image? I wasnā€™t able to make it work on my station

125

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).

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126

Frequencies and symbol rates are changed.

An updated script around the tools meteor_demod and meteor_decod found at dbdexter-dev (Davide Belloli) Ā· 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
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127

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

image

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