Hello timnan, and thanks for your question.
This quick answer is that, after a lot of searching, I was not able to
uncover a *definitive* specification of the CHRPT telemetry format.
It does not appear to be documented in any publicly-available source.
However, as you may or may not be aware, there are a number of
software packages that can consume CHRPT data, so it is doable.
According to the Chinese National Satellite Meteorological Center (
http://nsmc.cma.gov.cn/fy1e.html ):
"The High Resolution Picture Transmission of FY-1 C and D is named
CHRPT. It is considered that the system which receives and processes
HRPT/NOAA- Now data can receive and process CHRPT with updating as few
as possible.
The scan rate of MVISR is 6 lines/second. The words of every channel
are 2048 and the total words of 10 channels are 20480. Plus the sync
and auxiliary information there are 22180 words every scan line and 10
bits every word. The bit rate is 1.3308 Mbps, just twice as many as
the bit rate of HRPT/NOAA-Now. The modulation of CHRPT data is PSK and
bit format is split phase. The transmission frequency of CHRPT will be
1700.5MHz and the data format will be similar to the HRPT/NOAA-Now
data format. Therefor it will to be easy to process CHRPT data with
HRPT/NOAA-Now data processing system."
The link above also gives the basic channel information for FY-1C and
FY-1D.
The following page from the Geographic Information Systems Portal
gives similar information:
Meteorological satellite program of China
http://www.gisdevelopment.net/aars/acrs/1999/ts7/ts7212a.shtml
Now, one of the most widely-used packages for consuming all sorts of
weather satellite telemetry is the HRPT reader from David Taylor:
http://www.david-taylor.pwp.blueyonder.co.uk/software/hrpt.htm
On most sites devoted to weather satellite hobbyists, this program
seems to be the de facto standard for processing HRPT telemetry data.
From Mr. Taylor, I have received the exact frame layout for CHRPT,
which is appended to this answer. (If you cannot easily copy/paste
the layout, then I can arrange to put it somewhere more accessible.)
According to Mr. Taylor, this is the raw telemetry format, but if you
are working with data from other sources, then the files you get from
those sources may have additional header info or compression. I am
not sure if this applies to you, but since there does not appear to be
any available source of CHRPT data aside from getting it yourself
(unlike HRPT data which it easily obtainable from a variety of
sources), I am guessing this won't be a problem.
For your reference (although I suspect you already know), here is a
link to the NOAA HRPT data format, which you can compare to the CHRPT
frame to see that they are, indeed, quite similar:
http://www2.ncdc.noaa.gov/docs/klm/html/c4/sec4-1.htm
Since you mentioned that working with HRPT data has given you trouble
in the past, I also came across this link that documents some of the
variants of HRPT telemetry:
DSRS Satellite Data File Formats, Dundee Satellite Receiving Station
http://www.sat.dundee.ac.uk/formats.html
I hope this answers your question, and if you need any clarification,
please don't hesitate to ask.
Search strategy:
CHRPT data format
CHRPT telemetry format
HRPT data telemetry format
Summary of links:
FY-1C and FY-1D Specifications, Chinese National Satellite
Meteorological Center
http://nsmc.cma.gov.cn/fy1e.html
Meteorological satellite program of China, Geographic Information
Systems Portal
http://www.gisdevelopment.net/aars/acrs/1999/ts7/ts7212a.shtml
HRPT Programs - from David Taylor, Edinburgh
http://www.david-taylor.pwp.blueyonder.co.uk/software/hrpt.htm
NOAA KLM User's Guide, Section 4.1
http://www2.ncdc.noaa.gov/docs/klm/html/c4/sec4-1.htm
DSRS Satellite Data File Formats, Dundee Satellite Receiving Station
http://www.sat.dundee.ac.uk/formats.html
Appendix:
CHRPT data format (from David Taylor, mailto:davidtaylor@writeme.com )
|-----------------------------------------------------------------------------------------------------------------|
| CHRPT Frame Format (detailed)
|
|-----------------------------------------------------------------------------------------------------------------|
| Function | No of words | Word position | Bit number and meaning
|
|-----------------------------------------------------------------------------------------------------------------|
| Frame Sync | 6 | 1 | 1010000100 First 60
bits are a 63 bit PN generator started in the |
| | | 2 | 0101101111 all ones
state. The generator polynominal is |
| | | 3 | 1101011100 X^6 + X^5 +
X^2 + X + 1 |
| | | 4 | 0110011101
|
| | | 5 | 1000001111
|
| | | 6 | 0010010101
|
|-----------------------------------------------------------------------------------------------------------------|
| ID | 2 | 7 | 1-4 bit 1100
Satellite ID |
| | | 7 | 5-10 bit Spare word
|
| | | 8 | Spare word
|
|-----------------------------------------------------------------------------------------------------------------|
| Time Code | 4 | 9 | 1-9 bit binary day
count |
| | | 9 | 10 bit 0
|
| | | 10 | 1-3 bit 101
|
| | | 10 | 4-10 bit part of
binary millisecond of day count |
| | | 11-12 | part of
binary millisecond of day count |
|-----------------------------------------------------------------------------------------------------------------|
| Telemetry | 10 | 13-22 | Ramp calibration of 10
channels of MVISR |
| (Ramp) | | |
|
|-----------------------------------------------------------------------------------------------------------------|
| Telemtery | 10 | 23 | Temperature of first
stage of radiant cooler A |
| (Temp) | | 24 | Temperature of first
stage of radiant cooler B |
| | | 25 | Temperature of second
stage of radiant cooler A |
| | | 26 | Temperature of second
stage of radiant cooler B |
| | | 27 | Temp controlling
voltage of 2nd stage radiant cooler A |
| | | 28 | Temp controlling
voltage of 2nd stage radiant cooler B |
| | | 29-32 | Temp of sheath of
radiometer, 1 word per platinium resistance bulb |
|-----------------------------------------------------------------------------------------------------------------|
| Reference | 60 | 33-92 | 6 sampling words for
every channel |
| Black Body | | |
|
|-----------------------------------------------------------------------------------------------------------------|
| Space | 100 | 93-192 | 10 sampling words for
every channel |
|-----------------------------------------------------------------------------------------------------------------|
| Spare words | 1408 | 193-1600 | 00000 11101 Derived by
inverting the output of a 1023 PN sequence |
| | | | 00000 01100 prodived by
a feedback shift register generating the |
| | | | 10010 01010 polynominal
X^ + X^ + X^ + X^ + 1 |
| | | | ..... .....
|
| | | | 00100 11110
|
| | | | 11111 11000
|
| | | | 11000 01101
|
| | | | 11011 00101
|
|-----------------------------------------------------------------------------------------------------------------|
| Earth Data | 20480 | 1601-22080 | 2048 words for every
channels from channel 1 to channel 10. |
| | | | Each frame contains the
data obtained during one Earth scan of the |
| | | | MVISR sensor. The data
from the 10 sensor channels of the MVIRS |
| | | | are time multiplexed.
|
|-----------------------------------------------------------------------------------------------------------------|
| Aux. Sync | 100 | 22081-22180 | 11111 00010 Derived
from the non inverting output of a 1023 bit PN |
| | | | 11111 10011 sequence
provided by a feedback shift register |
| | | | 01101 10101 generating
the polynominal X^10 + X^5 + X^2 + X + 1 |
| | | | ..... .....
|
| | | | 01111 10000
|
| | | | 11110 01100
|
|-----------------------------------------------------------------------------------------------------------------| |
,
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