NOAA POES TIP Demodulation - Revision history

NebarnixWikiSysop: /* Todo */

2020-11-24T05:20:13Z

Todo

NebarnixWikiSysop: /* Latest News */

2016-10-26T12:36:05Z

NebarnixWikiSysop: /* Latest News */

2016-09-28T11:04:53Z

NebarnixWikiSysop: /* Latest News */

2016-09-28T11:03:46Z

NebarnixWikiSysop: /* Further Analysis */

2016-05-21T16:56:20Z

Further Analysis

NebarnixWikiSysop: /* Modulation Format */

2016-05-21T00:07:07Z

Modulation Format

NebarnixWikiSysop at 09:45, 20 May 2016

2016-05-20T09:45:59Z

NebarnixWikiSysop: /* Matlab Script */

2016-05-20T09:38:01Z

Matlab Script

NebarnixWikiSysop: /* HIRS/3 and HIRS/4 */

2016-05-20T09:33:46Z

HIRS/3 and HIRS/4

NebarnixWikiSysop: /* Raw IQ Recordings */

2016-05-20T09:30:59Z

Raw IQ Recordings

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 ==Todo==
-*Port GNU radio script to DSP code
+*Port GNU radio script to DSP code DONE
 *Maybe port this matlab script into sci-py and integrate directly into GNU radio block for realtime plotting and processing etc
 *Automate or improve automation of DCS geolocation (make it easier to map ALL transmitters with 3+ points in a single pass)

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 == Latest News ==
-I gave a talk at HeatSync Labs on this project!
+* I gave a talk at HeatSync Labs on this project! [https://www.youtube.com/watch?v=HjBMxoHTjCk "Reverse Engineering NOAA and ARGOS Satellite - Hot Topics - 9th September 2016"]
-[https://www.youtube.com/watch?v=HjBMxoHTjCk "Reverse Engineering NOAA and ARGOS Satellite - Hot Topics - 9th September 2016"]
+* Matlab code has been ported to a standalone C program that anyone can use! [https://github.com/nebarnix/Project-Desert-Tortoise The Project Desert Tortoise Github Page! ]
-Bumped this to the top as I have been porting the matlab code to a standalone C program that anyone can use! Check out the progress on:
+* Output of the demodulator can be opened with [https://github.com/nebarnix/PDT-TelemetryExplorer Telemetry Explorer], a QT based application with more and more functionality added all the time.
 ==Research==

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 I gave a talk at HeatSync Labs on this project!
-[https://www.youtube.com/watch?v=HjBMxoHTjCk]
+[https://www.youtube.com/watch?v=HjBMxoHTjCk "Reverse Engineering NOAA and ARGOS Satellite - Hot Topics - 9th September 2016"]
 Bumped this to the top as I have been porting the matlab code to a standalone C program that anyone can use! Check out the progress on:

← Older revision		Revision as of 11:03, 28 September 2016
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	== Latest News ==		== Latest News ==
		+	I gave a talk at HeatSync Labs on this project!
		+
		+	[https://www.youtube.com/watch?v=HjBMxoHTjCk]
		+
	Bumped this to the top as I have been porting the matlab code to a standalone C program that anyone can use! Check out the progress on:		Bumped this to the top as I have been porting the matlab code to a standalone C program that anyone can use! Check out the progress on:

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 ==Further Analysis==
 THE REST OF THE DCS DATA ON THIS PAGE HAS BEEN MOVED TO [[project_desert_tortoise | PROJECT DESERT TORTOISE]] PAGE!! Trying to contain the scope creep =D
 ==Todo==

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 I discovered that this is a very old modulation scheme, dating back to at least the late 60's. The scheme is a BPSK that uses a modulation index of 67 degrees to preserves the carrier for tracking purposes.
-It is also Manchester encoded, which means that even though the stream is 8320 bps, it is encoded using double the number of symbols, or 16,640 sps.
+It is also Manchester encoded, which means that even though the stream is 8320 bps, it is encoded using double the number of symbols, or 16,640 sps. The reason for this strange number is that there are 10 minor frames per second, and there happen to be 104 bytes per frame. Math :)
 ==GNU Radio Script==

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 [[Image:POES_waterfall.jpg|250px]]
 <br clear=both />
 ==Research==

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 <br clear="all">
-The circles are the locations where the sync word, "11101101 1110001 0000" appear. The bottom plot is a diff of the first, showing intervals of 832bits (minor frame length) which proves this is good data. The green dots are where there are Manchester encoding errors (two 1's or two 0's in a row not on a bit boundary). Note that there is no error correction, so I tried to make the manchester decoding as robust as possible by comparing the bit strength of both the first and second bit, and only using the value of the strongest one. The resynchronizer also only reacts if BOTH offending bits are very strong bits. It takes 32 seconds or 3200 minor frames to make up a whole major frame.
+The circles are the locations where the sync word, "11101101 11100010 000" appear. The bottom plot is a diff of the first, showing intervals of 832bits (minor frame length) which proves this is good data. The green dots are where there are Manchester encoding errors (two 1's or two 0's in a row not on a bit boundary). Note that there is no error correction, so I tried to make the manchester decoding as robust as possible by comparing the bit strength of both the first and second bit, and only using the value of the strongest one. The resynchronizer also only reacts if BOTH offending bits are very strong bits. It takes 32 seconds or 3200 minor frames to make up a whole major frame.
 [[Image:Syncword_manchester_errors.jpg|250px]]

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 ===HIRS/3 and HIRS/4===
-HIRS is a high resolution (I find this to be a relative term) infrared sounder. What it means is that there is a radiometer, a filter wheel with 20 channels, and a stepped mirror (with 55 positions) all in sync to produce a low resolution multispectral scan of the earth (and cal targets) basically by mechanical means.
+HIRS is a high resolution (I find this to be a relative term) infrared sounder. It consists of a radiometer, a filter wheel with 20 channels (narrow-band pass frequencies), and a stepped mirror (with 55 positions) all in sync to produce a low resolution multispectral scan of the earth (and cal targets including open space) by mechanical means.
-After spending a LOT of time fighting with NOAA-15 data (the best data I have as of Oct 07, 2015) I came to the conclusion that the HIRS/3 instrument was dead. By loading some much lower fidelity NOAA-18 data I could confirm that the actual radiometer data is all zeros in the NOAA-15 stream. The NOAA-18 data appears to have lots of values, and each channel can be made into an image 55 pixels wide which would be neat if I had better NOAA-18 data. NOAA-19 uses the HIRS/4 instrument and there are differences, but they seem to be mostly transparent to this script (images are still produced and make sense, though perhaps they are different wavelengths etc).
+After spending a LOT of time fighting with NOAA-15 data (the best data I have as of Oct 07, 2015) I came to the conclusion that the HIRS/3 instrument was dead*. By loading NOAA-18 data I could confirm that the actual radiometer data is all zeros in the NOAA-15 stream. The NOAA-18 data appears to have lots of values, and each channel can be made into an image 55 pixels wide which would be neat if I had better NOAA-18 data. NOAA-19 uses the HIRS/4 instrument and there are differences, but they seem to be mostly transparent to this script (images are still produced and make sense, though perhaps they are different wavelengths etc).
 ====Calculation of pixel size at nadir====
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 <br clear="both" />
-NOAA website confirms that the filter wheel motor for NOAA-15 has failed. [http://www.ospo.noaa.gov/Operations/POES/NOAA15/hirs.html]
+*NOAA website confirms that the filter wheel motor for NOAA-15 has failed. [http://www.ospo.noaa.gov/Operations/POES/NOAA15/hirs.html]
 ===SEM-2===

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 ==Raw IQ Recordings==
 * http://nebarnix.com/sdr/POES_56k250.raw 56.250khz IEEE 32-bit float raw IQ recording of the NOAA-15 beacon at 137.35Mhz
-* http://nebarnix.com/sdr/6_bits_dcblock2.raw IEEE 32-bit float raw IQ output from the GNU radio script at 1 symbol per sample to pull into matlab. Best recording to date, from reddit user _COD32_. NOAA-15.
+* http://nebarnix.com/sdr/6_bits_dcblock2.raw IEEE 32-bit float raw IQ output from the GNU radio script at 1 symbol per sample to pull into matlab. One of the best recordings to date, from reddit user _COD32_. NOAA-15 over Europe.
 ==Data Extraction and Validation==