Establishing radiometric consistency among VIIRS, MODIS, and AVHRR using SNO and SNOx methods

The launch of the SNPP with VIIRS signifies a new era of continued operational global earth observations with moderate resolutions. In the calibration/validation of VIIRS, it is essential to ensure that its measurements are consistent with those from previous instruments such as MODIS and AVHRR because longterm study of the earth relies on consistent satellite measurements with decadal data sets. This study focuses on the use of an extension of the traditional simultaneous nadir overpass (SNO) approach for performance evaluation and intercomparison of the VIIRS instrument with MODIS and AVHRR. Unlike SNO approach which is limited to polar regions only, the extended SNO (SNOx) provides an opportunity to compare satellite instruments at low latitudes over wide dynamic ranges. In addition, a new Geolocation Matching Method (GSM) method is developed to match a full VIIRS scene to MODIS. This tool uses an optimized algorithm with reduced run time and has been primarily used to analyze the intersatellite radiometric consistency and geolocation accuracy.