IN-FLIGHT VICARIOUS RADIOMETRIC CALIBRATION FOR VIS-NIR CHANNELS OF FY-1C SATELLITE SENSOR AT DUNHUANG SITE

First radiometric calibration for VIS-NIR channels of FY-1C meteorological satellite sensor was performed at China Dunhuang Calibration Test Site on July 7,16 and 17,1999.The radiometric calibration adopted the reflect ance-based method.First of all the ground reflectance at the test site and atmospheric parameters were obtained when FY-1C overpassed.Based on these data,a radiative transfer code (6S) was run.The apparent reflectance of FY-1Cs VIS-NIR channels was obtained.By geometric registration of the satellite-ground pixels and a comparison of the mean digital counts with the apparent reflect ance,the calibration coefficients (gain and of fset) from seven channels of FY-1C (center wavelength:455,505,555,630,865,932.5 and 1610nm) were determined.Anerror budget of the reflectance-based calibration method shows that the uncertainty is less than 7%.Comparing the calibration results with the prelaunch calibration,a better agreement at five channels is achieved except the ones in channels 9 (555 nm) and channel 6 (1610nm).Second radiometric calibration of VIS-NIR of FY-1C sat ellite sensor was made in September 2000.The results of the calibration monitored an at tenuation of FY-1C sat ellite sensor.The new calibration coefficients are import ant for quantita-tive application of FY-1C sat ellite observation data.