Study On Error Analysis And System Test For The Polarized Scanning Atmospheric Corrector

Atmospheric correction is an effective method to improve the quality of remote sensing data and the clarity and resolution of satellite optical remote sensing images.The correction effect depends on dimensions and accuracy of detected atmospheric optical parameters.Polarization remote sensing observation is currently a considerably reliable approach for the atmospheric correction as it can effectively eliminate the influence of surface background radiation and acquire higher aerosol inversion accuracy with more accurate atmospheric scattering model data,ultimately making atmospheric correction more accurate and sufficient.High-accuracy polarization measurement technology is not only the key to guarantee the inversion accuracy of aerosol parameters and atmospheric correction,but also the key technology of polarization remote sensing observation.This paper studied the influence factors,system calibration and detection methods of a high polarization measurement accuracy space-borne polarization scanner.This paper introduced the mathematical basis of polarization measurement technology,summarized different polarization measurement methods of data reduction algorithm,described the polarization measurement solutions and optical principle of the scanning-polarimetry and analyzed the critical design parameters.In addition,this paper gave an emphasis on comprehensive analysis of the polarization accuracy of the scanning-polarimetry.The error factors were purposely divided into the non-ideal errors caused by measuring methods and device features.Measuring method errors mainly includes errors from the misalignment of view field and the discrepancy of spectral characteristics,extinction ratio and transmissivity.The errors from device non-ideal features are mainly the errors caused by optical system and electronics system.For the non-ideality of optical system,the prism extinction ratio,prism azimuth angle,orthogonal lens set,and stray light were considered.The non-ideality of electronic system took account of the SNR and system linearity.After the abovementioned error factors were calculated and simulated on the basis of measurement equation of the scanning polarimeter.The simulation results show that the coincidence accuracy and spectral consistency of the field of view are relevant to the radiation characteristics of the tested target,and the difference of extinction ratio and transmittance could be corrected by subsequent calibration.Furthermore,the quantitative relations of polarization accuracy and prism extinction ratio,prism azimuth error,reflectance non-uniformity factor of orthogonal lens set,orthogonal angle error,stray light coefficient,signal-noise ratio and linearity were also given.The properties of calibration method and related detection methods were studied.According to the measuring equation,the calibration ratios were acquired,including extinction factor,prism azimuth angle,prism gain coefficients,polarization factors and the radiation intensity.The corresponding calibration methods,equipment as well as the scaling coefficients was successfully determined.Moreover,the detection of radiation,geometric test,the noise as well as the stray light was completed and the scan pointing accuracy and field overlap accuracy were obtained.Eventually,the evaluation and verification of polarization accuracy were made,demonstrating that the polarization accuracy of the scanning polarimeter was better than 0.5%(@p?0.3)under laboratory conditions.The polarization error factors of the scanning polarimeter were systematically studied,which can provide reference and guide for the application analysis of the instrument specification requirements and error control in the process of developing instrument.The method of polarization calibration studied in this paper is of great significance for eliminating non-ideal factors of the device and ensuring the accuracy of polarization measurement.Its radiation calibration method and the test of radiation performance are the standard to evaluate the accuracy of radiation measurement.The test results show that the polarization accuracy of the scanning polarimeter can be comparable with that of international similar instruments.