Spectral and radiometric calibrations for mapping satellite-1 camera

The spectral calibration and radiometric calibration were performed for every waveband of the Mapping Satellite-1 camera to validate its spectral and radiometric performance. In spectral calibration, a collimated monochromatic light source was provided by wavelength scan using a monochrometer and a collimator. Meanwhile, the camera acquired calibration images, and then compared image's digital number and the output of calibrated standard reference detector to obtain relative spectral responsive curve by data analysis and processing. Furthermore, spectral characteristics were acquired. In radiometric calibration, the nearest emitting source method was used to perform the end to end relative and absolute radiometric calibrations with irradiating the whole aperture and the field of view. In the on-orbit inner calibration, the aged and picked up LEDs were employed as on-orbit inner calibration light sources to monitor the changes and status of focal plane detector array and its imaging electric circuit at post launch, and they were corrected in necessary conditions. Spectral calibration and radiometric calibration results indicate that all the spectral performance and radiometric performance of the Mapping Satellite-1 camera meet design requirements, non-uniformity of the camera is decreased from 1.93% to 0.22% after relative radiometric calibration. The typical Signal to Noise ratios (SNRs) of panchromatic and multispectral cameras are beyond 90 times and 180 times respectively. The compared results from the on-board inter calibration after launching and the tested data from a laboratory before launching show that radiometric responsive performance of the camera has not changed during this period, and not need to be corrected. ©, 2015, Chinese Academy of Sciences. All right reserved.