Research On Key Characteristic Parameters Measurement And On-orbit Performance Evaluation Of Polarized Scanning Atmospheric Corrector

The complex and variable atmosphere is the primary non-sensor factor that affects the quality of Earth remote sensing images obtained by space-based optical remote sensing sensors.Accurate atmospheric correction can improve the quantitative level and application effectiveness of satellite remote sensing.Configuring a dedicated atmospheric correction payload that detects the same area as the corrected payload reduces the adverse impact of atmospheric spatiotemporal changes on atmospheric correction.The Polarized Scanning Atmospheric Corrector(PSAC)is mounted on the HJ-2 A/B to obtain atmospheric parameter information within a±32.5° field of view(800 km swath)through cross-track scanning,which is applied to atmospheric correction of wide-swath medium resolution multispectral camera and other payload images.The application effective of PSAC depends on the validity of observation results.By adding parameters and refining the model,payload characteristics can be characterized more accurately,and on-orbit dynamic continuous evaluation of key parameters can ensure the application effective throughout the life cycle.According to the working principle,operation environment and the of on-orbit application requirements of PSAC,this paper excavates the important characteristic parameters that may affect the detection effectiveness,including responsivity temperature dependence in the short-wave infrared(SWIR)bands,signal-to-noise ratio(SNR),radiometric calibrator,and dynamic range characteristics.Based on pre-launch characteristic parameter measurements and analysis,an on-orbit evaluation model and method were systematically constructed,the on-orbit performance evaluations of relevant characteristic parameters were achieved through PSAC on-orbit observation data.The research work mainly conducts research work in the following four parts:Established a measurement method for the temperature dependent characteristics of the responsivity of the SWIR channel detector,which solved the impact of the large temperature difference on the photosensitive surface of the SWIR detector on the detection accuracy of the PSAC.For the responsivity temperature dependence of the 2250 nm channel,the temperature coefficient of the detector responsivity was determined through instrument-level tests with thermal vacuum and laboratory temperature conditions.With this,the responsivity changes of the detectors caused by the satellite-laboratory cooling temperature difference was corrected and the on-orbit applicability of laboratory radiation measurements was guaranteed.Furthermore,an alternative detector-level experimental approach was explored and validated,which can effectively reduce the complexity and cost of experiments.A PSAC on-orbit SNR evaluation model was proposed,which met the urgent need of real-time evaluation of the on-orbit SNR under any radiance.Based on the noise composition and source analysis of PSAC,a signal-total noise power linear(STNPL)model based on the correlation between noise and signal is proposed,which realize on-orbit real-time SNR evaluation.Model parameters were obtained based on laboratory radiation measurement data.The dark reference response noise from the satellite was combined to evaluate the on-orbit SNR characteristics of PSAC.The SNR results evaluated with S-TNPL model were compared and verified with SNR calculations based on responses of the sun diffuser.Based on the actual characteristics of the radiometric calibrator on PSAC.the identification and measurement of calibrator characteristic parameters were improved,and on-orbit radiometric calibration and accuracy evaluation as well as the authenticity verification were carried out.Aiming at the sensitivity of the bidirectional reflectance distribution function(BRDF)to the solar incident geometry,the geometric characteristics of the stray light coefficient of the calibrator and the absolute BRDF of the sun diffuser were measured by a solar simulator and an absolute BRDF measurement system,and the absolute BRDF of the calibrator is obtained.With this,PSAC on-orbit calibration is realized based on the established PSAC on-orbit radiation calibration model,and the calibration accuracy is evaluated.Furthermore,on-orbit alternative calibration was carried out to verify the authenticity of the onorbit radiation calibration results.In response to the on-orbit application requirements of PSAC,a dynamic range scheme for PSAC was proposed and validation tested to ensure its detection performance for different targets.According to the satellite’s land observation requirements,the payload dynamic range,and on-orbit gain adjustment strategy were designed reasonably based on the typical radiance statistics of ground targets from international remote sensing instruments.The dynamic range performance of PSAC is evaluated in laboratory to ensure it coverages the most ground targets under the default gain and the flexible adaptability to other special targets observation.The onorbit dynamic range performance evaluation of PS AC was carried out,confirming the rationality and effectiveness of the dynamic range design and and ensure the on-orbit detection performance of PS AC.Through the measurement of characteristic parameters and the established onorbit evaluation method,the on-orbit evaluation of several characteristic parameters of PSAC is realized,which provides power support for ensuring the detection accuracy of atmospheric parameters and the application effect of atmospheric correction.It also provides a basis for researchers to evaluate the quality of remote sensing data.Some experimental methods and on-orbit evaluation methods in this study are exemplary and universal,it may provide reference for other remote sensors in laboratory measurement and on-orbit performance evaluation.