Suomi National Polar-Orbiting Partnership Visible Infrared Imaging Radiometer Suite polarization sensitivity analysis Applied Optics

The Visible Infrared Imaging Radiometer Suite (VIIRS) is one of five instruments onboard the Suomi National Polar-Orbiting Partnership (SNPP) satellite that launched from Vandenberg Air Force Base, California, on October 28, 2011. It is a whiskbroom radiometer that provides ±56.28° scans of the Earth view. It has 22 bands, among which 14 are reflective solar bands (RSBs). The RSBs cover a wavelength range from 410 to 2250 nm. The RSBs of a remote sensor are usually sensitive to the polarization of incident light. For VIIRS, it is specified that the polarization factor should be smaller than 3% for 410 and 862 nm bands and 2.5% for other RSBs for the scan angle within ±45°. Several polarization sensitivity tests were performed prelaunch for SNPP VIIRS. The first few tests either had large uncertainty or were less reliable, while the last one was believed to provide the more accurate information about the polarization property of the instrument. In this paper, the measured data in the last polarization sensitivity test are analyzed, and the polarization factors and phase angles are derived from the measurements for all the RSBs. The derived polarization factors and phase angles are band, detector, and scan angle dependent. For near-infrared bands, they also depend on the half-angle mirror side. Nevertheless, the derived polarization factors are all within the specification, although the strong detector dependence of the polarization parameters was not expected. Compared to the Moderate Resolution Imaging Spectroradiometer on both Aqua and Terra satellites, the polarization effect on VIIRS RSB is much smaller.

可见光红外成像辐射仪套件（Visible Infrared Imaging Radiometer Suite，VIIRS）是2011年10月28日从美国加利福尼亚州范登堡空军基地发射的苏奥米国家极轨伙伴卫星（Suomi National Polar-Orbiting Partnership，SNPP）所搭载的五台有效载荷之一。该仪器采用扫帚式扫描体制，可实现对地±56.28°的扫描视场覆盖。仪器共设置22个探测波段，其中14个为太阳反射波段（reflective solar bands，RSBs），波段覆盖波长范围为410 nm至2250 nm。遥感传感器的太阳反射波段通常对入射光的偏振特性具有响应。针对VIIRS，规范明确要求：在扫描角处于±45°范围内时，410 nm与862 nm波段的极化因子需小于3%，其余太阳反射波段的极化因子需小于2.5%。此前针对SNPP VIIRS开展了多次发射前极化灵敏度测试。早期开展的数次测试要么存在较大测量不确定性，要么可靠性不足，而最后一次测试被认为可提供该仪器偏振特性的精准表征数据。本文针对最后一次极化灵敏度测试的实测数据开展分析，从所有太阳反射波段的测量结果中推导出极化因子与相位角。所推导出的极化因子与相位角均与波段、探测器及扫描角相关；对于近红外波段，上述参数还与半角镜的侧别相关。尽管未预先料到极化参数存在显著的探测器依赖性，但所有推导出的极化因子均符合规范要求。相较于搭载于Aqua卫星与Terra卫星的中分辨率成像光谱辐射计（Moderate Resolution Imaging Spectroradiometer），VIIRS太阳反射波段的偏振效应要弱得多。