【作者】 董浩；

【导师】 洪津； 刘振海；

【作者基本信息】 中国科学技术大学 ， 光学， 2023， 博士

【摘要】 复杂多变的大气是影响空间光学遥感器对地遥感影像质量的最主要的非传感器因素。准确的大气校正可提高卫星遥感定量化水平及应用效果,通过同平台配置大气校正专用载荷获取同时同区域覆盖的大气参数,可降低大气时空变化对图像校正的不利影响。偏振扫描大气校正仪(Polarized Scanning Atmospheric Corrector,PSAC)搭载在环境减灾二号(HJ-2)A/B卫星上,以穿轨扫描方式实现±32.5°视场(幅宽800 km)内的大气参数信息获取,应用于宽幅中分辨多光谱相机等载荷图像的大气校正。PSAC的应用效果依赖于观测结果的有效性。通过增加参量并细化模型可以更准确地表征载荷特性,且关键参数的在轨动态连续评估可保证整个寿命内的应用效果。本文根据PSAC的工作原理、运行环境和在轨应用需求,挖掘了可能影响目标有效探测的重要特性参数,包括响应率温度依赖特性、信噪比特性、辐射定标器特性以及动态范围特性等;基于发射前特性参数测量和分析,系统构建了在轨评估模型和方法,并结合PSAC在轨观测数据实现了有关特性参数的在轨性能评估。本文主要开展了以下四部分的研究工作:建立了短波红外通道探测器响应率温度依赖特性测量方法,解决了探测器星-地工作条件下大温差对PSAC探测精度的影响。对于2250 nm波段的响应率温度依赖特性,通过热真空及实验室温不同环境下的仪器级实验测定了其响应率温度相关系数,校正了由于星-地运行温度差异导致的响应率变化,保证了实验室辐射测量结果的在轨适用性。此外,探索并验证了探测器级替代性实验方案,该方案可有效降低实验复杂性和成本。提出了 PSAC在轨信噪比评估模型,解决了在轨任意辐亮度下的信噪比评估难题。通过对PSAC的噪声构成及类型分析,提出了依据噪声与信号的相关性进行噪声分离的信号-总噪声功率线性(S-TNPL)模型,以此建立了在轨信噪比评估方法。基于实验室辐射测量数据获取了模型参数,并结合星上暗参考响应噪声,实现了 PSAC在轨信噪比特性评估。并通过与基于星上漫射板观测数据计算得到的信噪比结果进行了对比验证。基于PSAC星上辐射定标器实际特性,完善了定标器特性参数识别与测量,开展了星上辐射定标与精度评估和真实性检验。针对其双向反射分布函数(BRDF)对于太阳入射几何敏感的特点,分别通过太阳模拟器和BRDF测量系统测量获得定标器杂光系数的几何特性以及漫射板BRDF,获得了定标器的BRDF。基于所建立的PSAC在轨辐射定标模型实现了在轨定标,并评估了定标精度。同时还开展了在轨替代定标对星上辐射定标结果进行真实性检验。针对遥感器在轨应用需求,提出了 PSAC动态范围方案并开展了测试验证,保证了 PSAC对不同目标的探测性能。针对卫星的陆地观测需求,基于国际上典型遥感器的对地观测目标辐亮度统计结果,合理设计了载荷动态范围及在轨增益调整策略,在实验室测试评估了 PSAC动态范围性能,保证了在轨默认增益下对绝大部分地物动态范围的覆盖能力和对特殊目标观测的灵活适应性。开展了 PSAC在轨动态范围性能评估,确认了动态范围设计的合理性和有效性,保证了 PSAC在轨目标探测能力。通过特性参数测量及所建立的在轨评估方法,实现了 PSAC若干重要特性参数的在轨评估,为保证大气参数探测精度及大气校正应用效果提供有力支撑,也对研究人员开展卫星遥感器数据质量评估具有积极借鉴意义。在本文研究工作中,部分实验方法及在轨评估方法具有一定的示范性和通用性,可为其它遥感器改进实验室测量方法或者在轨性能评估研究提供借鉴和参考。更多还原

【Abstract】 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.更多还原