Report from CNSA 16th GSICS Executive Panel, Boulder, May 2015

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1 Report from CNSA 16th GSICS Executive Panel, Boulder, May 2015 Peng Zhang, Jun Gao

2 Satellite Introdution GF-1 satellite mission GF-1 satellite is the first CHEOS constellation satellite launched on April 26, 2013 Four Wide Field of View (WFV) sensors with the spatial resolution of 16m and 200km swath each. Two Panchromatic and Multi-Spectral (PMS) sensors with the spatial resolution of 8m(MS) and 2m(Pan). The swath is 60km by integrating two cameras. HY-2A satellite mission HY-2A satellite is the first ocean dynamics environment satellite in China Dual-band radar Altimeter (working on Ku-band and C-band) used to measure sea levels, significant wave heights and wind speeds Ku-band microwave Scatterometer for measuring sea surface wind field Scanning microwave Radiometer (6.6,10.7, 18.7, 23.8 & 37GHz) for measuring Sea surface temperature, atmospheric water vapor, et al. The design lifetime of HY-2A satellite is 3 years. By far, HY-2A satellite has been operating on orbit more than three years.

3 Land observing satellite-geometry Digital geometric calibration site in Yili, Xinjiang Area:100km*20km, scale: 1:1000 Digital geometric calibration site in Hebei Area:500km*100km, scale: 1:5000

4 GF-1 Operation phase After compared with MODIS over the Dunhuang calibration site, the radiometric stability of WFV camera is investigated. Then the radiometric calibration of WFV camera is accomplished with the reference MODIS sensor by means of the radiometric cross-calibration method.

5 GF-1 Operation phase Inter-cross calibration method is proposed to reduce the radiometric inconsistency of adjacent GF-1 WFV camera. Statistical analysis and simulation methods are adopted to build the correlation models of DN and TOA radiances between adjacent WFVs according to the overlap region of different phase image. Before After Before After WFV1 and WFV2 Before After WFV2 and WFV3 WFV3 and WFV4

6 HY-2 Commissioning Phase Examining the received telemetry of each instrument source packet for the HY-2A satellite and confirm whether the instrument telemetry is within the expected ranges. This activity is ongoing in operational phase. The synchronous observation experiment in the South China Sea is used to validate the significant wave height, sea surface temperature, wind vectors, air temperature, relative humility, air pressure, atmospheric sounding, et al. The HY-2A satellite product was validated by comparing with in-situ buoy (NDBC, Chinese, et al) observations, Jason-2 data, ASCAT, NCEP FNL Operational Global Analysis data,et al.

7 HY-2 Operation Phase Range absolute calibration: Based on the altimeter reconstructive transponder. The HY-2A altimeter receives the responding signals from the transponder and generates ranges. Pertinent reference ranges are obtained from the POD data and the transponder s coordinate. Using the ranges from the radar altimeter and the reference ranges, the time tag bias between the POD data and the HY-2A altimeter observations can be estimated. During the HY-2A altimeter calibration campaign from August 9, 2012, to July 20, 2014, 17 Fig. The HY-2A satellite altimeter transponder Fig. Time tag bias and the standard deviation of each HY-2A altimeter transponder measurement

8 HY-2 Operation Phase SSH : Using GPS buoys. In the first GPS buoy test experiment, the in-situ water levels jointly measured by the tidal gauge and the GPS buoy at Shazikou lasting for approximately 5 h were used to ensure the measurement homogeneity Fig. The GPS buoy test locations and field Fig. SSH observed by the GPS buoy and instruments tidal gauge

9 HY-2 Operation Phase For HY-2A altimeter: The SSH cross-calibration has been carried out using Jason-2 GDR product by crossover points. The altimeter product validation has been implemented by comparing with Jason- 2 GDR data and in-situ buoy observations. Sigma0 monitoring: Based on sigma0 measurement over Amazon Rainforest. Sigma0 calibration : Using scatterometer transponders and ocean calibration method. The wind vector validation : By comparing HY-2A altimeter products against in-situ NDBC buoy observations, ASCAT and NCEP FNL Operational Global Analysis data.

10 The follow-up plans and ideas Focus on the radiometric calibration of high spatial resolution observing satellite sensor (<30m) and gradually form the cross-calibration system of high spatial resolution observing satellite sensor. Start cross-calibration of HY-2 and JASON Start cross-calibration of thermal band of CERBS-04 with international sensors Start cross-calibration of GF-4 with international sensors