VIIRS Radiometric Stability over Salton Sea

The Visible Infrared Imaging Radiometer Suite (VIIRS) is a key instrument carried on the JPSS satellite series. One of its roles is to continue monitoring the long-term variations of Earth’s surface and atmosphere after MODIS. For this purpose, it is critically important to understand the VIIRS long-term radiometric stability through the time series analysis. The Salton Sea, a unique ecosystem located in Southern California, can be used as a calibration and validation site for satellite missions due to its homogeneous surface and low atmospheric water vapor content. In this study, VIIRS time series over the Salton Sea are used to evaluate the radiometric stability from both the operational Sensor Data Record (SDR) and the reprocessed SDR datasets. The scenes with clouds and land contaminations are removed based on the VIIRS cloud mask, the land water mask, and the uniform test. Since the satellite zenith angle has a significant impact on the measured reflectance for the visible bands, investigations will be conducted to understand its impact on the VIIRS long-term radiometric stability over the Salton Sea. The time series for all 5 imaging resolution bands (I-bands, I1-I5) and 16 moderate resolution bands (M-bands, M1-M16) are calculated and analyzed. Trends with confidence levels and standard deviations are examined to understand the long-term radiometric calibration stabilities of VIIRS/SNPP. The results show that most spectral bands exhibit insignificant trends, from both operational and reprocessed SDR datasets, suggesting VIIRS/SNPP’s strong radiometric stability. The reprocessed SDR shows slightly better results. To help understand the impact of cloud contamination on the trend quantification, an improved clear mask, based on the Gradient Boosting Decision Tree (GBDT) Algorithm from the machine learning technique, is developed and further investigated. The results from both the operational and the reprocessed SDR will be presented.