Abstract
Prelaunch radiometric characterization of the Day Night Band (DNB) of JPSS-1 VIIRS sensor was accomplished through a series of tests during environmental testing at Raytheon El Segundo in 2014. From these tests the calibration coefficients and key performance metrics linked to the sensor requirements such as sensitivity, dynamic range, and uniformity, are assessed. One complication in meeting these requirements, as well as the overall calibration uncertainty requirement, was the discovery of non-linearity in all DNB gain stages at low-radiance in the aggregation modes at the end of scan. During testing a use-as-is mitigation plan was developed by the vendor to the meet radiometric requirements at the expense of spatial resolution by eliminated the most affect aggregation modes at the end of scan.
The effects of the non-linearity remaining after mitigation to the on-orbit calibration algorithm will be explored especially on the mid and high gain stages. These gain states cannot be calibrated directly through the solar diffuser and rely on leveraging dynamic range overlap and an assumption of linearity to transfer the low gain stage calibration to the more sensitive gain stages. Thus this approach is particularly susceptible to non-linearity at the extremes of the dynamic range. A retrospective analysis of NPP-VIIRS DNB pre-launch test data is included to show the comparison of the impact in JPSS-VIIRS with data already in use by the science community.
Pre-Launch Radiometric Calibration of the S-NPP and JPSS-1 VIIRS Day/Night Bands
Prelaunch radiometric characterization of the Day Night Band (DNB) of JPSS-1 VIIRS sensor was accomplished through a series of tests during environmental testing at Raytheon El Segundo in 2014. From these tests the calibration coefficients and key performance metrics linked to the sensor requirements such as sensitivity, dynamic range, and uniformity, are assessed. One complication in meeting these requirements, as well as the overall calibration uncertainty requirement, was the discovery of non-linearity in all DNB gain stages at low-radiance in the aggregation modes at the end of scan. During testing a use-as-is mitigation plan was developed by the vendor to the meet radiometric requirements at the expense of spatial resolution by eliminated the most affect aggregation modes at the end of scan.
The effects of the non-linearity remaining after mitigation to the on-orbit calibration algorithm will be explored especially on the mid and high gain stages. These gain states cannot be calibrated directly through the solar diffuser and rely on leveraging dynamic range overlap and an assumption of linearity to transfer the low gain stage calibration to the more sensitive gain stages. Thus this approach is particularly susceptible to non-linearity at the extremes of the dynamic range. A retrospective analysis of NPP-VIIRS DNB pre-launch test data is included to show the comparison of the impact in JPSS-VIIRS with data already in use by the science community.