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LRPT

Page: Sats.LRPT - Last Modified : Sun, 19 Jun 11

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Meteor M1 LRPT downlink



OLD MODULATION FORMAT
 
Frequency:137.100 MHz
Modulation:QPSK
Rate: 72000 sym/s
Interleaving: None
Coding:Viterbi 1/2 + Reed Solomon
Scrambling:255byte sequence
Syncword:0x1ACFFC1D
S/C ID:0
 
Signal spectrum (click for full image):
NEW MODULATION FORMAT
 
Frequency:137.100 MHz
Modulation:QPSK
Rate: 80000 sym/s
Interleaving: 36/2048 (~8 seconds)
Coding:Viterbi 1/2 + Reed Solomon
Scrambling:255byte sequence
Syncword:0x1ACFFC1D
S/C ID:0
 
Signal spectrum (click for full image):


UPDATE 2010-01-15

Meteor-M1 is back to the old modulation format as specified above with no RS problems. Currently with channels 67 and 68, both with good IR imagery. Decoded images are below (20100115 1853z pass).

UPDATE 2010-01-13

After weeks of no IR imagery, passes on 2010-01-12 had channel 68 with some nice images - all still with non-CCSDS compatible RS. However on both passes on 2010-01-13 evening, all AC coefficients were zero for both 64 and 68 channels. This changes the signal spectrum slightly as it's sending a lot of zeroes. Also all frames still with bad RS.

UPDATE 2010-01-01

After two passes with with just added interleaver, Reed solomon encoder probably failed completely or was switched to some non-standard mode. RS block is still 128bytes at end of frame, non protected data are still same and can be decoded (with errors).
Possibilities are:

  • RS encoder failed - possible as there was problem with it before
  • switched to dual-basis mode as in CCSDS spefification - tried this, doesn't match
  • something with encoder order - like scrambling just input data, not RS checksum
  • wrong bit order somewhere in decoder
  • RS encoder use some different polynome and interleaving - unlikely

I have tried all combinations of scrambling before/after, dual-basis vs. normal mode, bit order swap before/after RS. Haven't found any way how to decode it properly. As first passes were using same RS as old format, I suspect is is failed RS encoder, not some new format of RS ECC.

UPDATE 2009-12-26

MERRY CHRISTMAS AND HAPPY NEW YEAR 2010
Downlink LRPT format changed and it's not 100% according to Metop LRPT specification. Scrambler seems to be working perfectly, spreading errors over few seconds and helping Viterbi to reconstruct more frames.
Format of actual frames is still same, so links below are still relevant.

Archive with raw decoded frames

I have uploaded archive with raw decoded frames (entire CCSDS 1024Byte frame, starting with SYNC) from last 3 passes (exact time & data is in file name):
Download: meteor-lrpt.rar (4MB) (raw received frames, no decoded images and no readable text inside)

List of PIDs active on all decoded passes:

DateTimevisvisIRIRvisctlNotes
200911031748z646566----70Vis only/black@night.
200911031928z646566----70Vis only/black@night.
200911041730z646566----70Vis only/black@night.
200911041907z646566----70Vis only/black@night.
200911051848z646566----70Vis only/black@night.
200911052028z646566----70Vis only/black@night.
200911061826z646566----70Vis only/black@night.
200911062004z646566----70Vis only/black@night.
200911081745z646566----70Vis only/black@night.
200911081929z646566----70Vis only/black@night.
200911091904z64----67687064,68=black@night 67=good
200911101842z64----67687064,68=black@night 67=good
200911102021z64----67687064,68=black@night 67=good
200911111821z64----67687064,68=black@night 67=good
200911191854z64----67687064,68=black@night 67=good
200911201653z64----67687064,68=black@night 67=good
200911201833z64----67687064,68=black@night 67=good
200911202010z64----67687064,68=black@night 67=good
200911211811z64----67687064,68=black@night 67=good
200911211949z64----67687064,68=black@night 67=good
200911221933z64----67687064,68=black@night 67=good
200911231728z64----67687064,68=black@night 67=good
200911231908z64----67687064,68=black@night 67=good
200911232051z64----67687064,68=black@night 67=good
200911241849z64----67687064,68=black@night 67=good
200911251827z------67687068=bad/low contrast 67=good
200911260959z------67687068=bad/low contrast 67=good
200911281903z------67687068=bad/low contrast 67=good
200911301822z------67687068=bad/low contrast 67=good
200911302000z------67687068=bad/low contrast 67=good
200912020747z------676870GRAYSCALE TEST PATTERN
200912020931z------676870GRAYSCALE TEST PATTERN
200912021742z------676870GRAYSCALE TEST PATTERN
200912021918z------676870GRAYSCALE TEST PATTERN
200912031051z646566----70encoder resets/long idle periods
200912031717z646566----70Vis only/black@night.
200912031858z646566----70Vis only/black@night.
200912032034z646566----70Vis only/black@night.
200912041838z64------6870Vis only/black@night.
200912042015z64------6870Vis only/black@night.
200912051955z64------6870Vis only/black@night.
200912081848z--65----6870Vis only/black@night.
200912091827z----66--6870Vis only/black@night.
200912092007z----66--6870Vis only/black@night.
200912110758z64----67--70encoder resets/long idle periods
200912110938z64----67--70encoder resets/long idle periods
200912111746z64----67--7064=black@night. 67=good
200912111925z64----67--7064=black@night. 67=good
200912121904z64----67--7064=black@night. 67=good
200912131843z64----67--7064=black@night. 67=good
200912141822z--65--67--7064=black@night. 67=good
200912171859z64--6667--70RS Encoder block #4 error
200912172044z----6667--70RS Encoder block #4 error
200912181838z6465----6870Vis only/black@night.
200912182023z6465----6870Vis only/black@night.
200912191817z6465----6870Vis only/black@night.
200912192001z6465----6870Vis only/black@night.
200912201939z6465----6870Vis only/black@night.
200912220727z6465--67--70encoder resets/long idle periods
200912220907z6465--67--70encoder resets/long idle periods
200912221853z6465--67--7064=black@night. 67=good
200912231833z6465--67--7064=black@night. 67=good
200912232013z6465--67--7064=black@night. 67=good
NEW DOWNLINK FORMAT
200912261853z64------6870No imagery.
200912261909z64------6870No imagery.
200912261735z64------6870Unknown RS used. No imagery.
200912261909z64------6870Unknown RS used. No imagery.
200912282008z64------6870Unknown RS used. No imagery.
200912291807z64------6870Unknown RS used. No imagery.
200912291950z64------6870Unknown RS used. No imagery.
200912301750z64------6870Unknown RS used. No imagery.
200912301929z64------6870Unknown RS used. No imagery.
200912311909z64------6870Unknown RS used. No imagery.
201001011847z64------6870Unknown RS used. No imagery.
201001021823z64------6870Unknown RS used. No imagery.
201001031802z64------6870Unknown RS used. No imagery.
201001041744z64------6870Unknown RS used. No imagery.
201001041920z64------6870Unknown RS used. No imagery.
201001051729z64------6870Unknown RS used. No imagery.
201001051905z64------6870Unknown RS used. No imagery.
201001061842z64------6870Unknown RS used. No imagery.
201001071818z64------6870Unknown RS used. No imagery.
201001081757z64------6870Unknown RS used. No imagery.
201001081936z64------6870Unknown RS used. No imagery.
201001091739z64------6870Unknown RS used. No imagery.
201001091919z64------6870Unknown RS used. No imagery.
201001101859z64------6870Unknown RS used. No imagery.
201001121817z64------6870Unknown RS used.
201001121956z64------6870Unknown RS used.
201001131756z64------6870Unknown RS used. All AC = zero
201001131935z64------6870Unknown RS used. All AC = zero
OLD DOWNLINK FORMAT AGAIN
201001151853z------676870Good imagery.
201001161658z------676870Good imagery.
201001161834z------676870Good imagery.
201001171812z------676870Good imagery.
201001171954z------676870Good imagery.
201001181752z------676870Good imagery.
201001181930z------676870Good imagery.
201001191910z------676870Good imagery. 137.9MHz
201001201850z------676870Good imagery. 137.9MHz
201001211830z------676870Good imagery.
201001212005z------676870Good imagery.
201001251708z------676870Good imagery.
201001251845z------676870Good imagery.
201001252026z------676870Good imagery.
201001261823z------676870Good imagery.
201001261958z------676870Good imagery.
201001271804z------676870No imagery.
201001271948z------676870No imagery.
201001281740z646566----70Vis only/black@night.

Sample images:

PID 64
(no good images so far)
 
PID 65
(no good images so far)
 
PID 66
(no good images so far)
 
PID 67
20091119 1854z

Eastern Europe/Russia
(enh/gamma 0.5/inv)


20091222 1853z

Nice pass over Europe
(enh/gamma 0.4/inv)


20100115 1853z

Pass over central Europe
(enh/gamma 0.4/inv)
 
PID 68
20091202 1918z

Test pattern



20100115 1853z

Pass over central Europe
(enh/gamma 0.4/inv)
 
PID 70
(data only)
 

(click thumbnails for full resolution images)


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