VIIRS/JPSS2 Day/Night Band Resolution Terrain Corrected Geolocation 6-Min L1 Swath 750m NRT

The Near Real Time (NRT) VIIRS/JPSS2 Day/Night Band Resolution Terrain Corrected Geolocation 6-Min L1 Swath 750m, short-name VJ203DNB_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 the single panchromatic Day-Night band (DNB). 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 provides geodetic coordinates (latitude and longitude), and related parameters for each VIIRS L1 pixel. The VJ203DNB product includes geodetic latitude, longitude, surface height above the geoid, solar zenith and azimuth angles, lunar zenith and azimuth angles, sensor zenith and azimuth angles, land/water mask, moon illumination fraction and phase angle, and quality flag for every pixel location.

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/JPSS-2 白昼/夜晚波段分辨率地形校正地理定位 6 分钟 L1 波段 750 米，简称 VJ203DNB_NRT，是基于联合极地轨道卫星系统-2（JPSS-2/NOAA-21）平台并由美国国家航空航天局（NASA）提供的VIIRS L1 地形校正地理定位产品，其中包含单色波段（白昼/夜晚波段，DNB）的视线（LOS）矢量。地理定位算法采用了地球椭球体、大地水准面、数字地形模型以及SNPP平台的星历和姿态数据，并结合了VIIRS传感器和卫星几何学的知识。该产品为每个VIIRS L1 像素提供了大地坐标（纬度和经度）以及相关参数。VJ203DNB 产品包括大地纬度、经度、相对于大地水准面的地表高度、太阳天顶和方位角、月天顶和方位角、传感器天顶和方位角、陆地/水域掩膜、月光照度分数和相位角，以及每个像素位置的质量标志。

J2 VIIRS 地理定位经历了在轨验证。对于图像分辨率波段和中等分辨率波段，沿扫描方向的地理定位误差约为 350 米，沿航迹方向的地理定位误差约为 165 米得到了校正。此外，白昼/夜晚波段（DNB）的地理定位误差约为 2000 米也得到了校正。进一步地，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航迹方向均降至 75 米（1-σ）以内。