1. FY-2 IR GSICS Correction Policy
Xiuqing (Scott) Hu
GPRC/NSMC/CMA
GSICS Web Meeting, July 26, 2011

2. FY-2 IR Calibration History
Before 2005: Earlier FY-2A/2B IR calibration based on Vicarious Calibration using Qinghai Lake and had no real time or near real time operational cal. Early sensor worked instably and has heavy stray light and didn’t have good geolocation
After 2005: FY-2C can work stably and VISSR IR operational calibration based on inter-calibration using AVHRR and HIRS since FY-2D also continues this kind of operational model since it begun to work in 2007.
After 2009: FY-2C/2D GSICS IR calibration experiment using the AIRS and IASI since Oct., Development of onboard half-optical BB calibration model based on GSICS reference standard.
After 2011: FY-2D/2E operational calibration monitoring test using GSICS IR calibration since May, 2011
After 2012: FY-2F/2G/2H completely operational calibration based on GSICS calibration using AIRS/IASI or CrIS and diurnally adjustment using half-optical BB after they will be launched
Retrospectively: Recalibration for FY-2C/2D/2E is conducted based inter-calibration using AIRS and IASI.
GSICS Web Meeting, July 26, 2011

3. Experiences from GSICS
GSICS is monitoring the FY-2 VISSR instruments calirabtion trend on orbit and indicates the annual and season fluctuation of operation calibration bias.
GSICS gives FY-2 VISSR a good independent radiance reference standard and enhances FY-2X calibration tie to international SI.
GSICS results verify the improvement of instrument manufacture step by step and provide positive feedback to the vendor.
GSICS provides a tie bridge of consistent calibration between geostationary FY-2 IR and polar orbiting FY-3 IR bands using the same GSICS advised sensors.
GSICS Web Meeting, July 26, 2011

4. GSICS Web Meeting, July 26, 2011

5. GSICS Web Meeting, July 26, 2011

6. FY-2E L1 calibration Bias with AIRS
GSICS Web Meeting, July 26, 2011

7. GSICS Web Meeting, July 26, 2011

8. GSICS Web Meeting, July 26, 2011

9. FY-2E has perfect consistence and stability of double difference between AIRS and IASI GSICS even if at colder reference targets. But there is bigger double difference in eclipse phase . This give us important indication of significant improvement of stray light in FY-2E than in FY-2C and FY-2D.
GSICS Web Meeting, July 26, 2011

10. FY-2X L1 Operational File
It is HDF5 format for storage and service to all data user. All L2 products generation of FY-2X is beginning from this kind of L1.
It is normal full disk with the constant geolocation grid (Nadir longitude:104.5E and 86.5E).
The Calibration LUTs (DN-Tbb) in L1 file are placed using the SDSs as the sort of channels.
GSICS Web Meeting, July 26, 2011

11. FY-2 IR current situation and GSICS Correction Policy
There is no reliable BB calibration of FY-2 by itself and have to depend on the other vicarious calibration, especially inter-calibration. But we found there is significant bias and large instability in operational calibration. GSICS gives an good chance for correct of FY-2 IR current calibration.
It is no meaning if we adapt the normal correction using the regression slope and offset between L1 and GSCS because of this kind of significant bias and instability.
We think that it is the best way if GSICS calibration result directly generates NEW LUT which is the same as the L1 format. This way for data user is very convenient and not needed to update the L2 code package.
The specific Implementation of GSICS Correction has two ways:
The independent LUT txt file on every day .
Add the GSICS new LUT SDS into the L1 HDF file (Named: GSICS_CALChannelIR1…)
Follow the GSICS Correction criterion in NetCDF output at the same time
GSICS Web Meeting, July 26, 2011

12. GSICS output file examples
CAL_LUT_FY2C_ORIG_X_ txt
CAL_LUT_FY2C_AIRS_0_ txt
GSICS output file examples
GSICS Web Meeting, July 26, 2011

13. GSICS two weekly reports since May 2011
GSICS Web Meeting, July 26, 2011

14. CMA GSICS Participants
GSICS EP
Dr. Peng Zhang
GRWG and GDWG
Mr. Xiuqing Hu (in GRWG)
Mr. Jingjing Liu (in GRWG)
Ms. Ling Sun (in GRWG)
Ms. Na Xu (in GRWG)
Mr Yong Zhang (in GRWG)
Mr. Zhiguo Rong (in GDWG)
Ms. Yuan Li (in GDWG)
Mr. Min Min (in GDWG)
Contact person for operation & product acceptance
Mr. Xiuqing
Ms. Yuan Li
GSICS Web Meeting, July 26, 2011