VIIRS geolocation accuracy is critical to not only the VIIRS products, but also the data product quality of all other instruments including CrIS, ATMS, and OMPS. This is because the VIIRS imagery bands have the highest spatial resolution compared to all other data on Suomi NPP and JPSS. The VIIRS geolocation determination is based on models of the Earth, orbital dynamics, instrument pointing, and timing. The accuracy of geolocation is affected by different source of errors, such as errors in ephemeris, attitude, instrument/platform alignment, and instrument internal geometry. Furthermore, the VIIRS geolocation also needs to take into account of the terrain effects. Given the complex process of determining the VIIRS geolocation, it is essential to monitor the performance of geolocation using ground truth. One method is to use high resolution imagery such as those from the Landsat as ground truth, using the control point matching algorithm to evaluate the geolocation errors. This is essentially the same algorithm for the MODIS geolocation developed by the NASA team. Separately, the VIIRS DNB geolocation at night is evaluated using point sources such as lights from oil platforms. The system now automatically generates the error assessments and makes the results available on line as shown below.
Spacecraft Attitude Monitoring