Research On Multi-site Cross-Calibration Of HJ-1/CCD Sensors

Absolute radiometric calibration of satellite is the foundation of quantitative application of Remote Sensing data. In order to improve the quality, utilization ratio and the quantitative application level of HJ-1/CCD Sensors data, it is needed to calibrate for HJ-1/CCD Sensors with high precision and frequency. For the current HJ-1/CCD Sensors research status of the single calibration method and the lack of credible calibration coefficient offset, this paper carried out the research on multi-site cross-calibration of HJ-1/CCD Sensors. Specific research includes the following three aspects:1) The improved cross-calibration formulas-in which spectra matching factor is defined as the ratio of normalized apparent reflectance of target sensor and standard sensor-are derived with a more concise and practical form. And then generalize the specific operation procedures of cross-calibration.2) The sources and size of cross-calibration uncertainty were analyzed, and the feasibility of various alternatives used non-measured data in cross-calibration process was discussed. Through the analysis, these conclusions are:the uncertainty of spectra matching factor caused by elevation setting, atmospheric parameter setting, substitution of history surface spectrum for synchronous measurement surface spectrum, and other factors is small (the uncertainty on the near infrared channels caused by water vapor setting is slightly larger); the actual type of surface feature is needed to be considered when the synchronous measurement surface spectrum replaced by a same type surface spectrum; and the uncertainty of spectra matching factor caused by surface bidirectional reflectance characteristics is great. In addition, the uncertainty of spectra matching factor under the same observation geometry is the minimum; the found of this nature provides another possibility for high-precision cross-calibration.3) The multi-site cross-calibration of HJ-1/CCD Sensors was carried out in this paper, and the in-orbit calibration coefficients (including the gain and offset)-which were proved to be reliable by validation of apparent products-was obtained.