Fy-1c polar orbiting meteorological satellite of china:
Satellite, ground system and preliminary applications
Yujie Liu, Wenjian Zhang, Yang Zongdong
National Satellite Meteorological Center (NSMC)
China Meteorological Administration (CMA)
Beijing 100081, P. R. China
Introduction
The first generation of polar orbiting
meteorological satellite project FY-1 series
has four satellites, FY-1A, 1B, 1C and 1D.
FY-1A and 1B were launched successfully
on September 7, 1988 and September 3,
1990 respectively. They were all
experimental satellites.
On May 10, 1999, FY-1C, the third polar
orbiting meteorological satellite with a ten-channel
radiometer as the primary sensing
instrument, was launched successfully. The
FY-1C satellite was designed and
manufactured by the Ministry of Aerospace
of China according to the requirement
specified by China Meteorological
Administration (CMA). The successful
launching of FY-1C is a major development
in Chinese scientific and technological
modernization of meteorology. With
launching of this satellite, we have ability to
get the remote sensing data not only over
China but also over the world. This data will
be useful in analysis of meteorology.
hydrology, climate research, agriculture and
environment mornitoring. To compare with
FY-1A and 1B, FY-1C is more advanced.
It has been providing observing data to users
over the world every day since the first day
after launch. It is in operation now.
The Characteristics of FY-1C
FY-1C is a hexahedron of 1.42m x 1.42m x
1.2m. With three solar cell arrays, the total
length of the satellite is 10.556m. The
attitude of FY-1C is 3-axis stabilized with an
accuracy less than 0.5 degrees. The designed
life time is two years. The orbit parameters of
FY-1A, 1B and 1C are in table 1.
Table 1 The orbit parameters of FY-1A, 1B and 1C
| Satellite | FY-1A | FY-1B | FY-1C |
| Launch date | September 7,1988 | September 3, 1990 | May 10, 1999 |
| Orbit | Sun-synchronous | Sun-synchronous | Sun-synchronous |
| Altitude (km) | 901 | 901 | 863 km |
| Period (minutes) | 102.86 | 102.86 | 102.301minutes |
| Inclination (degrees) | 99.0 | 98.9 | 98.79 |
| Eccentricity | <0.005 | <0.005 | <0.00188 |
| Descending Node(LST) | 03:30 | 07:50 | 08:34-09:00 |
| Attitude Control | Three-axis stabilized | Three-axis stabilized | Three-axis stabilized |
Sensor Specification
The main payload on board the satellite
includes two 10-channel VIS/IR scanning
radiometers working in a mutual back up
mode, they can be switched according to the
tele-command. MVISR is the new
instrument. The most significant change to
the MVISR is ten channels sensor, including
4 VIS channels, 3 near IR channels, 1 short
wave IR channel and 2 long wave IR
channels. Table 2 is the specification of
MVISR. To compare with FY-1A and 1B,
the new channels have been added are used
to aid in improved snow and cloud
discrimination and aerosol detection as well
as heat source detection for forest fire
monitoring, SST and Water vapor
calculation and so on. It enables the more
powerful observations to the land and oceans.
The instantaneous field of view of the
MVISR is 1.2
mrad, which makes 1.1 km
resolution at the sub-satellite point. The
channel characteristics and purpose of the
radiometer are shown in Table 3.
Table 2 The Specification of MVISR
| Scan Rate | 6 line/pre second |
| Channels | 10 |
| Word/pre scan line | 2048 for HRPT and LDPT 1018 for GDPT |
| Scan Angle | ±55.4° |
| Sub-point resolution | 1.1km |
| Quantification level | 10bit |
| Calibration accuracy | VIS and Near-IR 5 - 10%r
IR ±1K(300K)
|
Table 3 The Channel Characteristics and
Purpose of MVISR
| Channel | Wavelength (mm) | Primary Use |
| 1 | 0.58-0.68 | Daytime cloud, ice and snow, vegetation |
| 2 | 0.84-0.89 | Daytime cloud, vegetation |
| 3 | 3.55-3.95 | Heat source, night cloud |
| 4 | 103.-11.3 | SST, day/night cloud |
| 5 | 11.5-12.5 | SST, day/night cloud |
| 6 | 1.58-1.64 | Soil moisture, ice/snow distinguishing |
| 7 | 0.43-0.48 | Ocean color |
| 8 | 0.48-0.53 | Ocean color |
| 9 | 0.53-0.58 | Ocean color |
| 10 | 0.90-0.985 | Water vapor |
Characteristics of Data Transmission
The data transmission has several upgrades to
FY-1A and 1B. There are three data
transmission mode on board of FY-1C,
HRPT, GDPT or LDPT.
HRPT is the High Resolution Picture
Transmission. The format is very similar to
NOAA/HRPT, except that the data
transmission rate is 1.3308 Mbps. The
transmission modulation is PSK and bit
format is split phase. The transmission
frequency is 1700.5Mhz.
GDPT and LDPT are delayed picture
transmission. The on board data storage
capacity is 300 minutes. Therefore, FY-1C
satellite and the ground system can receive
the Global Area Coverage (GAC) data for
four selected channels (channel 1,2,4,5) with
reduced resolution in 4 km for day time
only(defined as Delayed Global Picture
Transmission). As an alternative, the ground
system can also receive 20 minutes orbit
observational data for ten channels with the
original resolution at any region of the world
with the on board data storage capacity
(defined as Delayed Local Picture
Transmission, DLPT). As same as HRPT,
the data transmission rate of GDPT and
LDPT are 1.3308 Mbps. The transmission
modulation is PSK and bit format is split
phase. The transmission frequency is
1708Mhz.
