Eplee Robert E, Turpie Kevin R, Meister Gerhard, Patt Frederick S, Franz Bryan A, Bailey Sean W
Appl Opt. 2015 Mar 10;54(8):1984-2006. doi: 10.1364/AO.54.001984.
The NASA Ocean Biology Processing Group (OBPG) developed two independent calibrations of the Suomi National Polar-Orbiting Partnership (SNPP) Visible Infrared Imaging Radiometer Suite (VIIRS) moderate resolution reflective solar bands using solar diffuser measurements and lunar observations, and implemented a combined solar- and lunar-based calibration to track temporal changes in radiometric response of the instrument. Differences between the solar and lunar data sets have been used to identify issues and verify improvements in each. Linearization of the counts-to-radiance conversion yields a more consistent calibration at low radiance levels. Correction of a recently identified error in the VIIRS solar unit vector coordinate frame has been incorporated into the solar data and diffuser screen transmission functions. Temporal trends in the solar diffuser stability monitor data have been evaluated and addressed. Fits to the solar calibration time series show mean residuals per band of 0.067%-0.17%. Periodic residuals in the VIIRS lunar data are confirmed to arise from a wavelength-dependent libration effect for the sub-spacecraft point in the output of the U.S. Geological Survey Robotic Lunar Observatory photometric model of the Moon. Temporal variations in the relative spectral responses for each band have been assessed, and significant impact on band M1 (412 nm) lunar data has been identified and rectified. Fits to the lunar calibration time series, incorporating sub-spacecraft point libration corrections, show mean residuals per band of 0.069%-0.20%. Lunar calibrations have been used to adjust the solar-derived radiometric corrections for bands M1, M3, and M4. After all corrections, the relative differences in the solar and lunar calibrations for bands M1-M7 are 0.093%-0.22%. The OBPG has achieved a radiometric stability for the VIIRS on-orbit calibration that is commensurate with those achieved for SeaWiFS and Aqua MODIS, supporting the incorporation of VIIRS data into the long-term NASA ocean color data record.
美国国家航空航天局海洋生物学处理组（OBPG）利用太阳漫射器测量数据和月球观测数据，对苏梅国家极地轨道伙伴关系（SNPP）可见红外成像辐射计组（VIIRS）的中分辨率反射太阳波段进行了两次独立校准，并实施了基于太阳和月球的联合校准，以跟踪该仪器辐射响应的时间变化。太阳数据集和月球数据集之间的差异已被用于识别问题并验证各自的改进情况。在低辐射水平下，计数值到辐射率转换的线性化产生了更一致的校准。VIIRS太阳单位矢量坐标框架中最近发现的误差校正已纳入太阳数据和漫射器屏幕传输函数。已对太阳漫射器稳定性监测数据的时间趋势进行了评估和处理。对太阳校准时间序列的拟合显示，每个波段的平均残差为0.067%-0.17%。VIIRS月球数据中的周期性残差被证实是由美国地质调查局月球机器人观测站月球光度模型输出中，航天器下方点的波长依赖性天平动效应引起的。已评估了每个波段相对光谱响应的时间变化，并识别和纠正了对波段M1（412纳米）月球数据的重大影响。结合航天器下方点天平动校正的月球校准时间序列拟合显示，每个波段的平均残差为0.069%-0.20%。月球校准已用于调整波段M1、M3和M4的太阳衍生辐射校正。经过所有校正后，波段M1-M7的太阳校准和月球校准的相对差异为0.093%-0.22%。OBPG已实现VIIRS在轨校准的辐射稳定性，这与SeaWiFS和Aqua MODIS所实现的辐射稳定性相当，支持将VIIRS数据纳入美国国家航空航天局的长期海洋颜色数据记录。
