FY1 C and D Polar Orbiting Spacecraft

FY-1C was launched at 0133Z 10 May 1999 on a CZ-4B vehicle from Taiyuan.
International Designator - 1999-025A
NORAD Catalog Number - 25730
CHRPT Transmission frequency - 1700.4 MHz (actual), 1700.5 MHz (published)

FY-1D was launched at 0150Z 15 May 2002 on a CZ-4B vehicle from Taiyuan.
International Designator - 2002-024B
NORAD Catalog Number - 27431
CHRPT Transmission frequency - 1700.4 MHz

Spacecraft Characteristics
Parameter | Item
Orbit altitude | 870 Kilometers
Inclination | 98.85°
Eccentricity | < 0.005
Orbtial period | 102.301 minutes
Sensor | Multichannel Visible and IR Scan Radiometer (MVISR). This instrument is a 10 channel sensor with 4 vis, 3 near IR, 1 short IR and 2 long IR. The IFOV is 1.2 mrad with a nadir resolution of 1.1km

MVISR Characteristics
Channel | Wavelength | Primary use
1 | 0.58-0.68 | Daytime cloud, ice and snow, vegetation
2 | 0.84-0.89 | Daytime cloud, vegatation, WV calibration
3 | 3.55-3.95 | Night cloud
4 | 10.3-11.3 | SST, day/night cloud
5 | 11.5-12.5 | SST, day/night cloud
6 | 1.58-1.64 | Soil humidity, ice/snow separation
7 | 0.43-0.48 | Ocean colour
8 | 0.48-0.53 | Ocean colour
9 | 0.53-0.58 | Ocean colour
10 | 0.90-0.985 | Water vapor

FY1-C High Resolution Picture Transmission (CHRPT)
As the MVISR is now 10 channel instead of 5, the bit rate has been increased to 1.3308 Mbps, exactly twice the current HRPT bit rate.
The scan rate is 6 lines/sec with 2048 10 bit words per channel per line plus sync and auxiliary infromation (ie 22,180 10-bit words per line).
Transmission frequency - 1700.5 MHz (Prime) or 1704.5 MHz (back-up).
EIRP - +39.4 dBm
Polarization - Right Hand Circular
Modulation -PCM/BiPhase-Level/PSK
Modulation Index - +/-67.5 +/- 7.5 deg;
Bit Rate -1.3308 Mbps
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CHRPT Frame Format (from CGMS-XXV PRC WP-02)

CHRPT Frame Format
Function | Frame Sync | ID | Time Code | Telemetry (Ramp) | Telemetry (Temperature) | Black Body | Space Data | Spare | Earth Data | Aux Data
Number of Words | 6 | 2 | 4 | 10 | 10 | 60 | 100 | 1408 | 20480 | 100

CHRPT Parameters
Number of words in a frame - 222180
Number of channels - 10 with 2048 words per channel
Frame Rate - 6 frames/sec
Number of bits of word - 10 bits /word
Bit Rate - 1.3308 Mbps
Bit Format - Split-phase with a data "1" as high to low level and data "0" as low to high level at the data mid-bit

Detailed CHRPT Frame Format
Function | Number of words | Word position | Bit number 12345678 90 | Meaning
Frame Sync | 6 | 1 2 3 4 5 6 | 1010000100 0101101111 1101011100 0110011101 1000001111 0010010101 | First 60 bits are a 63 bit PN generator, started in the all ones state. The generator polynominal is X^6 + X^5 + X^2 + X + 1
Identification | 2 | 7 | 1-4 bit | Satellite ID - binary 1100
|  | 7 | 5-10 bit | Spare bits
|  | 8 |  | Spare word
Time Code | 4 | 9 | 1-9 bit | Binary day count
|  | 9 | 10 bit | binary 0
|  | 10 | 1-3 bit | binary 101
|  | 10 | 4-10 bit | Binary part of millisecind of day count
|  | 11-12 | 1-10 bit | Binary part of millisecind of day count
Telemetry (Ramp) | 10 | 13-22 |  | Ramp calibration of 10 channels of MVISR
Telemetry (Temp) | 10 | 23 |  | Temperature of the first stage of radiant cooler A
|  | 24 |  | Temperature of the first stage of radiant cooler B
|  | 25 |  | Temperature of the second stage of radiant cooler A
|  | 26 |  | Temperature of the second stage of radiant cooler B
|  | 27 |  | Temperature controlling voltage of the second stage of radiant cooler A
|  | 28 |  | Temperature controlling voltage of the second stage of radiant cooler B
|  | 29-32 |  | Temperature of sheath of radiometer, one word for each platinium resistance bulb
Reference Black Body | 60 | 33-92 |  | 6 sampling words for every channel
Space Data | 100 | 93-192 |  | 10 sampling words for every channel
Spare words | 1408 | 193 194 | 1599 1600 | 0000011101 0000001100 | 1100001101 1101100101 | Derived fron the inverted output of a 1023-bit PN sequence provided by a feedback shift register generating the polynominal : X^10 + X^5 + X^2 + X + 1. The generator is started in the all ones state at the beginning of word 7
Earth Data | 20480 | 1601-22080 |  | 2048 words for every channel from channel 1 to Channel 10. Each frame contains the data obtained during on Earth scan of the MVISR sensor. The data from the 10 sensor channels of the MVISR are time multiplexed.
Auxiliary Sync | 100 | 22081 22082 | 22179 22180 | 1111100010 1111110011 | 0111110000 1111001100 | Derived fron the non-inverted output of a 1023-bit PN sequence provided by a feedback shift register generating the polynominal: X^10 + X^5 + X^2 + X + 1. The generator is started in the all ones state at the beginning of word 22081

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FY-1C Delayed Picture Transmission (CDPT)
. Playback of recorded data of 4 channels at 4 km resolution
. Only available over groundstations in China on 1708.5 MHZ (Prime) or 1695.5 MHz (backup)
. No other details available

Note - There will no APT transmission from FY1 C.