为实现高分一号卫星宽视场成像仪的实时辐射定标, 准确获取成像仪在轨暗电流噪声引起的偏移量信息, 提出了高频次辐射定标方法, 并分析了方法的可靠性和测算精度。介绍了卫星遥感器在轨辐射定标原理。以敦煌辐射校正场为实验区, 利用该场地历史光谱数据和实时气象观测数据确定了高频次定标的数据基准。基于成像仪夜间大面积海洋场景数据测算了偏移量信息, 即在无辐射能量输入的条件下, 测算成像仪自身暗电流噪声引起的输出数值。然后, 利用地面参考基准数据和偏移量信息, 实现了高分一号卫星宽视场成像仪的在轨定标。最后, 分析和检验了高频次定标方法的不确定性和定标结果的可靠性。结果表明: 高分一号卫星宽视场成像仪高频次定标的不确定度小于5.3%; 基于该定标结果获取的辐亮度产品与基于官方定标结果获取的辐亮度总体相对偏差小于5.6%; 基于夜间海洋场景计算的定标截距(即偏移量)更接近于理论设计值。该方法可用于高分一号卫星宽视场成像仪的在轨定标和暗电流噪声定期检测。

To realize real-time radiometric calibration of a wide field-of-view sensor on the GF-1 satellite and to obtain offset information caused by dark-noise signals of the WFV sensor, a high-frequency calibration method was established and the reliability and precision of this method were researched and analyzed. Firstly, the in-flight radiometric calibration theory was introduced, and the reference benchmark of calibration data was established by using historical spectral reflectance data and real-time atmosphere profiles of Dunhuang test site. The offset was calculated based on a nighttime offing observing image, which is the digital number signal output from the sensor in the condition of naught radiance input. Then the WFV sensor of GF-1 satellite was calibrated by using the reference data from ground and the offsets prepared. Finally, the uncertainty of this method and accuracy of calibration results were analyzed and validated. Experimental results indicate that the uncertainty of high-frequency calibration of WFV sensor is less than 5.3%, and the difference between radiance based on high-frequency calibration coefficients and radiance with official promulgation publicized results is lower than 5.6%. The offset, calibration intercept, calculated with nighttime sea image accords with the theoretical design value, meanwhile, the calibration method can satisfy the requirement of the in-flight calibration and dark-noise detection of the WFV sensor on GF-1 satellite periodically.