[Automatic Field Calibration and Analysis of Satellite Based on Hyper-Spectral Ratio Radiometer].

With the demand of calibration technology of high frequency and high precision in terms of the optical remote sensing satellite of China, and the deficiency of the artificial work, the automatic system of hyper-spectral ratio radiometer was developed by investigation the calibration situation of domestic and abroad satellite, then the automatic calibration of satellite sensor was carried out. According to the parameters demand of field calibration and the goal of automation, the ratio radiometer was designed to measure global spectral irradiance by integrating sphere, and the diffuse spectral irradiance was measure by the shelter, so the diffuse-global ratio was calculated by these data. Simultaneity the ground radiation was measured with radiometer optical-lens and the automatic observation of atmospheric and surface radiation characteristics was achieved, In addition, the data pre-processing of real-time and remote transmission were integrated in the system. With the field test on the Dunhuang radiometric calibration sites in 2015, the radiometer worked in an ideal way, and the atmospheric optical parameters and surface reflectance data were acquired, which support the calibration of satellite sensor. The comparison with the traditional measurement was carried, the relative deviation of the surface reflectance is less than 5%, and the absolute deviation of the atmospheric parameters is less than 5% and the diffuse ratio is less than 0.015%. According to the measured data and based on irradiance-based method, the field calibration applied to the band 1~5 of Aqua MODIS, the relative deviation of band 1~4 is less than 1% while the band 57.24%, so the requirement of the automatic calibration of the satellite sensor was satisfied preliminarily.

[Stokes Parameter Detection and Precision Analysis Based on Rotating Quarter-Wave Plate].

The accuracy of the calibration reference source polarization states directly influences the precision of the polarized optical remote sensor calibration, and thus affects the inversion accuracy of the characteristics of targets. In this paper, 870 nm horizontal linear polarized light has been chosen as the tested calibration reference light, modulated by rotating quarter-wave plate(QWP). The intensity as a Fourier series of the rotation angle of the plate and its coefficients were demodulated with the Fourier transform method, Stokes parameters can be calculated with these coefficients. The mean, standard deviation, composite uncertainty and relative deviation of measured data compared with the theoretical value of the ten measurement results were presented. In order to improve the accuracy of the measurement, the correction model for the quarter-wave plate retardance deviation Δδ, fast axis angle deviation Δα and the transmission axis alignment deviation Δß of analyzing polarizer has been constructed. In this model, detection deviation of Stokes parameters is described as a function of Δδ and Δß, Δδ and Δß were determined by the function and magnitude of the deviation. Combined with quarter-wave plate fast axis angle deviation which was the result of simulation to adjust the experiment device, and then detecting the calibration reference source polarization states again. The experimental results show that, the difference between measured value and theoretical value of Stokes parameters reduced to less than 1.41% from 3.77% relative to without correction. The experiment principle, device and deviation correction model of this research can significantly improve the accuracy of detecting the polarization state of the calibration reference light source.