Sun Junqiang, Wang Menghua
Appl Opt. 2015 Jan 10;54(2):236-52. doi: 10.1364/AO.54.000236.
We analyze bidirectional reflectance factors (BRF) of the solar diffuser (SD) and vignetting function (VF) of the SD screen (SDS) for on-board calibration of the visible infrared imaging radiometer suite (VIIRS). Specific focus is placed on the products of the BRF and VF, which are the main inputs for calibration of the SD and its accompanying solar diffuser stability monitor (SDSM), which tracks SD degradation. A set of 14 spacecraft yaw maneuvers for the Suomi National Polar-Orbiting Partnership satellite, which houses the VIIRS instrument, was carefully planned and carried out over many orbits to provide the necessary information on the dependence of VIIRS instrument response on solar angles. Along with the prelaunch measurements for the SDS VF and SD BRF, the absolute form of the BRF-VF product is determined for each of the reflective solar bands (RSB) and the SDSM detectors. Consequently, the absolute form of the SDS VF also is obtained from the RSB and SDSM detectors using the yaw maneuver data. The results show that the BRF-VF product for an RSB is independent of the detector, gain status, and half-angle mirror side. The derived VFs from the RSB and the SDSM detectors also show reasonable agreement with each other, as well as with the prelaunch VF measurements, and further demonstrate only geometrical dependence, which, in this work, is characterized by solar angles. The derived calibration coefficients, called the F-factors, from the application of the derived functions in this study show a significantly improved pattern. A small band-dependent residual seasonal fluctuation on the level of ∼0.2%-0.4% remains in the F-factors for each RSB and is further improved by a corrective function with linear dependence on the solar azimuth angle in the nominal attitude instrument coordinate system to the VF. For satellite ocean color remote sensing, on-orbit instrument calibration and characterization are particularly important for producing accurate and consistent ocean color products. The result of this work has the most significant and direct impact on ocean color products.
我们分析了用于可见红外成像辐射计套件（VIIRS）在轨校准的太阳漫射器（SD）的双向反射率因子（BRF）和SD屏幕（SDS）的渐晕函数（VF）。特别关注BRF和VF的乘积，它们是用于校准SD及其随附的太阳漫射器稳定性监测器（SDSM）的主要输入，SDSM用于跟踪SD的退化。为搭载VIIRS仪器的苏梅国家极地轨道伙伴关系卫星精心规划并在多个轨道上执行了一组14次航天器偏航机动，以提供关于VIIRS仪器响应与太阳角度相关性的必要信息。连同SDS VF和SD BRF的发射前测量，针对每个反射太阳波段（RSB）和SDSM探测器确定了BRF-VF乘积的绝对形式。因此，还使用偏航机动数据从RSB和SDSM探测器获得了SDS VF的绝对形式。结果表明，RSB的BRF-VF乘积与探测器、增益状态和半角镜侧无关。从RSB和SDSM探测器导出的VF彼此之间以及与发射前VF测量结果也显示出合理的一致性，并且进一步证明仅存在几何相关性，在本工作中，这种相关性由太阳角度表征。在本研究中，通过应用导出函数得到的称为F因子的导出校准系数显示出显著改善的模式。每个RSB的F因子中仍存在约0.2%-0.4%水平的小波段相关残余季节性波动，通过在标称姿态仪器坐标系中对VF与太阳方位角呈线性相关的校正函数可进一步改善这种波动。对于卫星海洋颜色遥感，在轨仪器校准和特性描述对于生成准确且一致的海洋颜色产品尤为重要。这项工作的结果对海洋颜色产品具有最显著和直接的影响。
