Solar reflection band of typical in-orbit payload was calibrated by the use of the Dunhuang site automatic observation radiometric calibration operational system (DARCOS) in 2018. Several automatic observation instruments were installed at Dunhuang site. DARCOS integrated product generation, acquisition, archiving, publishing, retrieval, downloading, user hierarchical management and performance monitoring functions together. Automatic calibration algorithm for AQUAMODIS, JPSS1VIIRS, FY2GVISSR, FY3CVIRR and FY4AAGRI were developed. How to accurately measure the surface reflectance without human intervention and correct it to the payload viewing angle is an important subject needs to be solved. A surface reflectance algorithm based on surface radiance and total sky radiation was developed. The directionality calibration was performed using the micro-facet cosine linear kernel-driven (MICOKE) BRDF model. The reflectance was corrected by the site vicarious calibration campaign on August 7-9, 2018. The site correction factor exhibits two variations rules with increasing wavelength, which corresponds to the HIM detector design. The calibration results for 5 payloads between August 13 and December 31, 2018 were analyzed. Ratio of the apparent reflectance from space and ground base was used to judging the agreement. AQUAMODIS (1.02-1.15), JPSS1VIIRS (1.07-1.15), and FY3CVIRR(1.10 to 1.19) are in good agreement with the automatic observation products of the site. FY2GVISSR (1.25) and FY4AAGRI (1.07-1.31) show differences changing by time. As an efficient independent calibration method, automatic calibration could be an effective supplement to the in-orbit calibration.
A brand-new field observing station has been built up in the China radiometric calibration sites (CRCS) of Dunhuang Gobi for CAL/VAL, include house, observing field, power supply, tower crane, et al. Many automatic observation instruments designed and manufactured by Anhui Institute of Optics and Fine Mechanical Chinese Academy of Sciences were deployed in CRCS Dunhuang Site and introduced deeply in this paper. Followed with the finishing of the basic constructions of the field observing station, it will be an open field test and exchange platform for sharing of test data, research and infrastructure, promote exchanges and cooperation between the relevant disciplines and units.
Meteorological satellites have become an irreplaceable weather and ocean-observing tool in China. These satellites are used to monitor natural disasters and improve the efficiency of many sectors of Chinese national economy. FY-2 series satellites are one of the key components of Chinese meteorological observing system and application system. In this paper, the operational satellite- FY-2D’s infrared channels were focused and analyzed. The instruments’ background was introduced briefly. The main payload SVISSR specifications were compared with its ancestral VISSR. The optical structure of the SVISSR was also expressed. FY-2D prelaunch calibrations methodology was introduced and the accuracies of the absolute radiometric calibration were analyzed. Some key optics on-orbit performance of FY-2D SVISSR were analyzed include onboard blackbody, cold FPA and detector noise level. All of these works show that FY- 2D’s main payload SVISSR was in a healthy status.
FY-2D is the second Geostationary Operational Meteorological Satellite of China and launched on December 08, 2006. With the launch of FY-2D, Chinese geostationary meteorological satellite observing system formatted of the first binary mode, greatly improving the timeliness of meteorological satellite cloud images. In this paper, the optical structure of the SVISSR onboard FY-2D was introduced. Some key optics on-orbit performances of FY-2D SVISSR were analyzed, including onboard blackbody and cold FPA. The onboard blackbody calibration models were set up and the methodologies were also introduced step by step. Base on the GSCIS calibration results, the model coefficients were determined. The historical FY-2D satellite data were also recalibrated with these models. Based on the comparisons of the calibration coefficients between onboard calibration models, cross calibration with AIRS and operational calibration coefficient in product, the conclusion can be drawn that the calibration results from blackbody models and cross calibration with AIRS were better than operational calibration results in product. The calibration results of blackbody models were agreed well to the cross calibration with AIRS, but the frequency of calibrations with blackbody models were much higher than cross calibration with AIRS. The onboard blackbody calibration models of FY-2D SVISSR based on GSICS can be used to calibrate the satellite infrared data operationally.
The China-Brazil Earth Resources Satellite (CBERS) was developed by China in cooperation with Brazil. As one of the most important payload, CCD camera is expected to play an important role in the application of CBERS. Vicarious calibrations have been conducted every one year and cross-calibration is one of the methods to the calibration. Our effort is to probe the methodology of radiometric cross-calibration the CCD with MODIS and detect the degradation of the CCD camera since it was launched. The radiometric and reflectance coefficients and offsets for four CCD spectral bands were obtained based on the cross-calibration with four calibration targets. Results were validated by the synchro surface targets spectral measurement at Dunhuang site. The TOA radiances from calculation and simulation were consistent within 1%. Comparing our results with the coefficients based on vicarious calibration show that the average variation of the two independent methods was with 6%. Based on many times of radiometric-cross calibration of the CCD with the MODIS, the time series of radiometric coefficients for the CCD were obtained. Results illuminated that the response of the CCD have degraded, which could reach up to 3%- 7% per month
TERRA MODIS band 31 was selected as the criterion for doing the radiometric cross-calibration of CBERS-02 IRMSS band 9 in this paper. From August to December, 2004, seven times day and night synchronous images of two sensors passing through the Lake Qinghai and Lake Taihu were selected to get the cross-calibration data. Using TERRA MODIS band 31 data to conduct out the at pupil radiance of CBERS-02 IRMSS band 9 based on the two sensors' spectrum matching, and then pick-up the DN values from the IRMSS data in the same area. A new model to calculate the radiometric calibration coefficients was carried out in this paper: multi-points linear regression method with 7 times day and night synchronous images at different dates and locations. This new method can obviously control the radiometric calibration uncertainties aroused by the single point method to do the in-flight calibration like CBERS-02 IRMSS, this kind of sensors can't collect the radiometric signals from the deep space. In this research, the radiometric calibration coefficients obtained through the linear regression method were 8.0567 (gain, unit: DN/ (W/m2/sr1/μm1))
and 47.892 (offset, unit: DN). Preliminary estimate of calibration coefficients using Shanghai area was carried out and the results showed that the calibration coefficients obtained from the linear regression method was with a similar precision to TERRA MODIS band 31's. This suit of calibration coefficients can satisfy the quantitative applications of CBERS-02 IRMSS thermal data.