NOAA ARGOS TX - Revision history

NebarnixWikiSysop at 16:54, 21 May 2016

2016-05-21T16:54:07Z

2016-05-21T16:53:22Z

2016-05-21T16:53:02Z

Todo

2016-02-04T10:53:19Z

2016-02-04T02:51:03Z

2015-10-29T15:14:02Z

2015-10-29T15:07:20Z

2015-10-28T16:18:51Z

added DCS data to back up results

2015-10-28T15:21:06Z

2015-10-28T15:16:47Z

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 ==Problem statement ==
-I need to find a transmitter that I know is in a certain locale for validating the [[NOAA_POES_TIP_Demodulation]] DCS-2 Doppler shift models. I also want to figure out the time base encoding contained inside of the DCS packets, which I assumed were 100ms but the numbers aren't quite adding up. Also, who doesn't want to decode a new and exciting signal?!
+I need to find a transmitter that I know is in a certain locale for validating the  [[project_desert_tortoise | PROJECT DESERT TORTOISE]]  a subset of the  [[NOAA_POES_TIP_Demodulation]] DCS-2 Doppler shift models. I also want to figure out the time base encoding contained inside of the DCS packets, which I assumed were 100ms but the numbers aren't quite adding up. Also, who doesn't want to decode a new and exciting signal?!
 To be useful, we need to decode the bits of the transmitter to find the 4-byte ID that we will use to find the data in the satellite downlink data.

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 * DONE!! Figure out the location of this transmitter using radio direction finding techniques while being respectful of the science and careful not to invade on private property (this includes the transmitter as well as its surroundings) in order to get more exact tuning of the doppler shift geolocation model.
 * DONE!! Run the doppler model and plot the results.
-* Finish https://github.com/nebarnix/Project-Desert-Tortoise/blob/master/README.md SO THE WORLD CAN JOIN IN THE FUN
+* Finish https://github.com/nebarnix/Project-Desert-Tortoise SO THE WORLD CAN JOIN IN THE FUN

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 [[File:DopplerCurveFit.jpg|250px]] [[File:DopplerModelResultsVisualization2.jpg|250px]] [[File:DopplerModelResultsVisualization1.jpg|250px]] [[File:DopplerModelResults.jpg|250px]] [[File:DopplerModelResults3vs4.jpg|250px]]
 ===Todo===
-* Figure out the location of this transmitter using radio direction finding techniques while being respectful of the science and careful not to invade on private property (this includes the transmitter as well as its surroundings) in order to get more exact tuning of the doppler shift geolocation model.
+* DONE!! Figure out the location of this transmitter using radio direction finding techniques while being respectful of the science and careful not to invade on private property (this includes the transmitter as well as its surroundings) in order to get more exact tuning of the doppler shift geolocation model.
-* Run the doppler model and plot the results.
+* DONE!! Run the doppler model and plot the results.

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 Which decodes to <br/>
-'''Preamble''': F E2 F0<br/>
+'''Preamble''': String of ~16 0x0 or 0xF <br/>
 '''TXID''': FB 3A D0 00 <br/>
 '''Data''': 00 00 0

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 This TXID shows up in nearly every data set that I have, and appears to be a strong transmitter. It should be a good data verification source! The TXID appears to transmit nothing at all, which could mean it is simply meant to be tracked and really doesn't contain any data payload, or there could be events that trigger status words to appear (low battery, etc) though I have yet to observe this behavior.
 ===Todo===
 * Figure out the location of this transmitter using radio direction finding techniques while being respectful of the science and careful not to invade on private property (this includes the transmitter as well as its surroundings) in order to get more exact tuning of the doppler shift geolocation model.
 * Run the doppler model and plot the results.

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 Using the satellite data to frame our packet, we can now conclusively say that this transmitter is transmitting the following bits.
-11111111 11100010 11110000 - 11111011 00111010 11010000 00000000 00000000 00000000 0000<br/>
+<pre>
 Preamble   Sync     Sync        ID       ID      ID        ID      Data     Data   Data
 Which decodes to <br/>

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 ==ARGOS Description==
-ARGOS transmitters are environmental monitors that uplink data to the NOAA POES spacecraft. They broadcast preserved carrier manchester encoded BPSK on 401.650Mhz. The bitrate is 200bps and the symbol rate is 400bps and the payload is up to 48 bytes. The repetition rate is around a minute, but can be more or less. Their location is calculated by using the recorded doppler shifts, and the orbit of the satellite. This is often a lower power alternative to GPS, though they could transmit GPS coordinates as their payload as well. Ocean sensors, floats, wave height monitors, arctic sea ice monitors, and wildlife tracking collars are some examples.
+ARGOS transmitters are environmental monitors that uplink data to the NOAA POES spacecraft. They broadcast preserved carrier manchester encoded BPSK on 401.650Mhz. The bitrate is 400bps and the symbol rate is 800bps and the payload is up to 48 bytes. The repetition rate is around a minute, but can be more or less. Their location is calculated by using the recorded doppler shifts, and the orbit of the satellite. This is often a lower power alternative to GPS, though they could transmit GPS coordinates as their payload as well. Ocean sensors, floats, wave height monitors, arctic sea ice monitors, and wildlife tracking collars are some examples.
 ==Local Transmitter==

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 What is ID? what is sync word? What is payload? There are many ways to find out, but the best way I could think of was to search for three bytes at a time within the satellite downlink data, since it should contain the ID and the payload.
-Bingo. '11111011001110101101000000000000' match found (ID 165 in dataset 8; ID 50,257,378 in dataset 5)
+Bingo. '11111011001110101101000000000000' match found (ID 165 in dataset 8; ID 50,257,378 in dataset 5)<br/>
 Using the satellite data to frame our packet, we can now conclusively say that this transmitter is transmitting the following bits.