Skakun Sergii, Justice Christopher O, Vermote Eric, Roger Jean-Claude
Department of Geographical Sciences, University of Maryland, College Park, MD, USA.
NASA Goddard Space Flight Center Code 619, Greenbelt, MD, USA.
Int J Remote Sens. 2018;39(4):971-992. doi: 10.1080/01431161.2017.1395970. Epub 2017 Jul 5.
The Visible/Infrared Imager/Radiometer Suite (VIIRS) aboard the Suomi National Polar-orbiting Partnership (S-NPP) satellite was launched in 2011, in part to provide continuity with the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument aboard National Aeronautics and Space Administration's (NASA) Terra and Aqua remote sensing satellites. The VIIRS will eventually replace MODIS for both land science and applications and add to the coarse-resolution, long term data record. It is, therefore, important to provide the user community with an assessment of the consistency of equivalent products from the two sensors. For this study, we do this in the context of example agricultural monitoring applications. Surface reflectance that is routinely delivered within the M{O,Y}D09 and VNP09 series of products provide critical input for generating downstream products. Given the range of applications utilizing the normalized difference vegetation index (NDVI) generated from M{O,Y}D09 and VNP09 products and the inherent differences between MODIS and VIIRS sensors in calibration, spatial sampling, and spectral bands, the main objective of this study is to quantify uncertainties related the transitioning from using MODIS to VIIRS-based NDVI's. In particular, we compare NDVI's derived from two sets of Level 3 MYD09 and VNP09 products with various spatial-temporal characteristics, namely 8-day composites at 500 m spatial resolution and daily Climate Modelling Grid (CMG) images at 0.05° spatial resolution. Spectral adjustment of VIIRS I1 (red) and I2 (near infra-red - NIR) bands to match MODIS/Aqua b1 (red) and b2 (NIR) bands is performed to remove a bias between MODIS and VIIRS-based red, NIR, and NDVI estimates. Overall, red reflectance, NIR reflectance, NDVI uncertainties were 0.014, 0.029 and 0.056 respectively for the 500 m product and 0.013, 0.016 and 0.032 for the 0.05° product. The study shows that MODIS and VIIRS NDVI data can be used interchangeably for applications with an uncertainty of less than 0.02 to 0.05, depending on the scale of spatial aggregation, which is typically the uncertainty of the individual dataset.
搭载在苏米国家极地轨道伙伴关系（S-NPP）卫星上的可见/红外成像仪/辐射计套件（VIIRS）于2011年发射，部分目的是与美国国家航空航天局（NASA）的Terra和Aqua遥感卫星上的中分辨率成像光谱仪（MODIS）仪器保持连续性。VIIRS最终将在陆地科学和应用方面取代MODIS，并补充粗分辨率的长期数据记录。因此，向用户群体提供对这两种传感器等效产品一致性的评估非常重要。在本研究中，我们在农业监测应用示例的背景下进行了此项评估。M{O,Y}D09和VNP09系列产品中常规提供的地表反射率为生成下游产品提供了关键输入。鉴于利用从M{O,Y}D09和VNP09产品生成的归一化植被指数（NDVI）的应用范围以及MODIS和VIIRS传感器在校准、空间采样和光谱波段方面的固有差异，本研究的主要目标是量化与从使用MODIS到基于VIIRS的NDVI转换相关的不确定性。具体而言，我们比较了从两组具有不同时空特征的三级MYD09和VNP09产品得出的NDVI，即空间分辨率为500米的8天合成数据和空间分辨率为0.05°的每日气候建模网格（CMG）图像。对VIIRS的I1（红色）和I2（近红外 - NIR）波段进行光谱调整，以匹配MODIS/Aqua的b1（红色）和b2（NIR）波段，以消除基于MODIS和VIIRS的红色、近红外和NDVI估计之间的偏差。总体而言，对于500米产品，红色反射率、近红外反射率、NDVI不确定性分别为0.014、0.029和0.056，对于0.05°产品分别为0.013、0.016和0.032。研究表明，根据空间聚合尺度，MODIS和VIIRS的NDVI数据可互换用于不确定性小于0.02至0.05 的应用，这通常是单个数据集的不确定性。
