1. An introduction of FY2 and its Lunar calibration
Lin Chen, Ronghua Wu, Xiuqing Hu
CMA/National Satellite Meteorological Centre
Outline
General description of the satellite and sensor
Progress of the Lunar calibration of FY2
Feedback for discussions
国家卫星气象中心
Lunar Calibration Workshop

2. General description (1)-Satellte
Launch Day
Sat. Name
Status
Subpoint
Sensor
batches
10,Jun. 1997
FY-2A
Test;Decommissioned
105°
VISSR
First
25,Jun.2000
FY-2B
Test,Decommissioned
10,Oct.2004
FY-2C
Operational,partly Decommissioned
123°
SVISSR
Second
08,Dec.2006
FY-2D
Operational,on-orbit
86.5°
23,Dec.2008
FY-2E
13,Jan.2012
FY-2F
112.5°
Third
XX, Dec.2014
FY2G
will be launched

3. General description (2)-Sensor
Sensor Specification
spectral bands
5 bands including
1 VIS band and
4 IR bands
resolution
1.25km for VIS
5km for IR
Earth scan angle
20°*20°
scan sampling
10000 scan for VIS band
2500 scan for IR bands
scan time
0.15s for VIS
0.6s for IR
Quantization
6bit for VIS(0~63)
10bit for IR(0~1064)
IFGOV
35urad for VIS
140urad for IR
There is a big improvement for FY2F VIS band. The SRF is more narrow and move to shorter wavelength with less absorption.
Four detectors of FY2F VIS band are Consistent

4. General description (3)-on-board calibration
The onboard blackbody calibration facility for the IR bands
cannot be used for absolute calibration, and is
only a valuable tool for monitoring detector response.
Eclipse Phase
Scenes radiance
BB radiance
1. There is no on-board VIS calibrator for FY2;
2. The operational calibration table is pre-launched result
and never changed on-orbit;
3. The DCC method and Dunhuang Gobi are used for
vicarious calibration.

5. General description (4)-Challenges
challenges in lunar calibration for FY2 1
Low Quantization Level: 6bit
~0.5% / DN ( DN <16)
~2%/ DN( DN >=16) 2
Stray light is a big problem especially for
FY2D and FY2E;
FY2F improved this issue greatly.

6. Lunar calibration(1) -Moon acquisition
Lunar forecast
EUMETSAT helped us to forecast the moon position
The Normalized Geostationary Projection file (HDF format)do not contain the moon image. We should get moon image from Compressed full disk VISSR data, which is binary format.
Data preparation
Moon selection
Automatic acquisition moon image by the 400*400 box
FY2 VIS resolution on moon:( )*tg(35urad)≈14.28km
FY2 Moon pixels: /14.28≈243 (over-sampling is not considered)

7. Lunar calibration(2) -Example of an image

8. Lunar calibration(3)-Some considerations
Dark signal correction
We choose the lunar image on the right side of FY2 full disk. So the dark signal is 0;
Integration step
calculate the radiance of each moon pixel
by using calibration table.
sum all the pixels in the box to get the
irradiance
Oversampling consideration:
we should know the speed and movement
direction of moon . ?
similar image of GEOS;
from Stone, et al. 2005

9. Lunar calibration(4)-files preparation
SRFs for FY2D/E/F are prepared by Masaya.
The FY2 lunar input file is not ready. I am trying to write the input files for FY2. So no result is displayed

10. Lunar calibration(5)-Operation of the GIRO
result
GIRO is running
GIRO demo is successfully operated on a virtual machine. The virtual machine is created by VMware workstation software.

11. Feedback for discussions
How to calculate the oversampling factor?
Maybe more feedback when I successfully run the GIRO for FY2.

12. …… Stop Here
Thanks very much ! 12