VIIRS/JPSS2 Moderate Resolution Terrain Corrected Geolocation 6-Min L1 Swath 750m NRT

The Near Real Time (NRT) VIIRS/JPSS2 Moderate Resolution Terrain Corrected Geolocation 6-Min L1 Swath, short-name VJ203MOD_NRT) is the Joint Polar-orbiting Satellite System-2 (JPSS-2/NOAA-21) platform-based NASA VIIRS L1 terrain-corrected geolocation product, and contains the derived line-of-sight (LOS) vectors for each of the 750-m moderate-resolution, or M-bands. The geolocation algorithm uses a number of inputs that include an Earth ellipsoid, geoid, and a digital terrain model along with the SNPP platform's ephemeris and attitude data, and knowledge of the VIIRS sensor and satellite geometry. It produces geodetic coordinates (latitude and longitude), and related parameters for each VIIRS L1 pixel. The VJ203MOD product includes geodetic latitude, longitude, surface height above the geoid, solar zenith and azimuth angles, sensor zenith and azimuth angles, land/water mask, and quality flag for every pixel location. VJ203MOD provides a fundamental input to derive a number of VIIRS M-band higher-level products.

The J2 VIIRS geolocation underwent an on-orbit validation. Geolocation errors of about 350 m in the along-scan direction and about 165 m in the along-track direction were corrected for the image-resolution bands and moderate-resolution bands. The Day-Night band (DNB) geolocation error of about 2000 m was corrected. Further, the geolocation biases in the scan profile were also corrected. All these corrections bring the geolocation uncertainties for the J2 L1 products to within 75 m (1-sigma) in both the along-scan and along-track directions.

近实时（NRT）VIIRS/JPSS2中分辨率地形校正地理定位6分钟L1带状数据（简称VJ203MOD_NRT），是基于联合极地轨道卫星系统-2（JPSS-2/NOAA-21）平台的美国国家航空航天局（NASA）VIIRS L1地形校正地理定位产品，包含750米中分辨率，或称M波段，的每个波段的导出视线（LOS）向量。地理定位算法采用了地球椭球体、大地水准面和数字地形模型等众多输入，并结合SNPP平台的天体视差数据和姿态数据，以及对VIIRS传感器和卫星几何形状的了解。该算法生成每个VIIRS L1像素的地理坐标（纬度和经度）及相关参数。VJ203MOD产品包括大地纬度、经度、相对于大地水准面的表面高度、太阳天顶和方位角、传感器天顶和方位角、陆地/水域掩膜以及每个像素位置的质量标志。VJ203MOD为推导出多个VIIRS M波段高级产品提供了基本输入。

J2 VIIRS地理定位经历了在轨验证。沿扫描方向的地理定位误差约为350米，沿轨道方向的地理定位误差约为165米，针对图像分辨率波段和中分辨率波段进行了校正。日夜波段（DNB）的地理定位误差约为2000米也得到了校正。此外，扫描剖面中的地理定位偏差也得到了校正。所有这些校正使得J2 L1产品的地理定位不确定性在沿扫描和沿轨道方向均降至75米（1倍标准差）以内。