Sun Junqiang, Wang Menghua, Jiang Lide, Xiong Xiaoxiong
Appl Opt. 2019 Aug 20;58(24):6655-6665. doi: 10.1364/AO.58.006655.
The follow-on Visible Infrared Imaging Radiometer Suite (VIIRS) housed in the NOAA-20 satellite was launched on 18 November 2017. It has 22 spectral bands, among which 14 are reflective solar bands (RSBs) covering the wavelength range from 411 to 2258 nm. Prelaunch polarization sensitivity measurements have revealed that NOAA-20 VIIRS RSBs are much more sensitive to polarization of the incident light than its predecessor, the VIIRS on the Suomi National Polar-orbiting Partnership. For the short wavelength bands, i.e., M1-M4, the polarization sensitivities are out of specifications, especially for band M1, for which the polarization factors can be as large as ∼6%. The polarization effect induces striping in imagery along the track and radiometric bias both along the scan and along the track, resulting in much larger uncertainties in the environmental data records (EDR). In this paper, the polarization effect correction algorithms are described and applied to the NOAA-20 VIIRS RSBs for ocean scenes where the top-of-atmosphere radiance can be separated into the ocean normalized water-leaving radiance, the basis of the ocean color EDR, and the sunlight reflected by the atmosphere, which can be mostly described by the Rayleigh scattering radiance. The errors of the sensor data records (SDR or Level-1B radiance) due to the polarization effect can be as large as ∼1% for bands M1 and M2, and those in the ocean normalized water-leaving radiances are about 13% and 10% for wavelengths at 411 nm (band M1) and 445 nm (band M2), respectively. The polarization effect also induces strong striping in both NOAA-20 VIIRS RSB SDR and normalized water-leaving radiances. It is demonstrated that with the polarization correction applied, the aforementioned errors and artifacts are successfully removed.
搭载于NOAA - 20卫星上的后续可见红外成像辐射计套件（VIIRS）于2017年11月18日发射。它有22个光谱带，其中14个是反射太阳波段（RSB），覆盖波长范围从411至2258纳米。发射前的偏振灵敏度测量表明，NOAA - 20 VIIRS的RSB对入射光偏振的敏感度比其前身——苏米国家极轨伙伴关系卫星上的VIIRS要高得多。对于短波长波段，即M1 - M4，偏振灵敏度超出规格，特别是对于波段M1，其偏振因子可达约6%。偏振效应会在沿轨道的图像中产生条纹，以及在扫描和沿轨道方向上产生辐射偏差，从而导致环境数据记录（EDR）中的不确定性大幅增加。在本文中，描述了偏振效应校正算法，并将其应用于NOAA - 20 VIIRS的RSB，用于海洋场景，在该场景中，大气顶辐射可分为海洋归一化离水辐射（海洋颜色EDR的基础）和大气反射的太阳光，后者主要由瑞利散射辐射描述。由于偏振效应，传感器数据记录（SDR或1B级辐射）的误差对于波段M1和M2可达约1%，而在411纳米（波段M1）和445纳米（波段M2）波长处，海洋归一化离水辐射的误差分别约为13%和10%。偏振效应还会在NOAA - 20 VIIRS的RSB SDR和归一化离水辐射中都引起强烈条纹。结果表明，通过应用偏振校正，上述误差和伪像得以成功消除。
