A Status on JPSS-VIIRS Series: Cross-Comparison of Sensor Radiometric Performance Based on Ground Testing

Two of the Visible Infrared Imaging Radiometer Suite (VIIRS) instruments are successfully operating on-orbit, SNPP and JPSS-1 (J1), sending high quality measurements needed to generate a large set of environmental data products that are used in various fields of science and applications. SNPP and J1 VIIRS were launched on October 28, 2011 and November 18, 2017, respectively, while the third VIIRS sensor on the JPSS-2 (J2) spacecraft just completed its ground sensor level testing in February 2018. All VIIRS instruments have very similar design, with multiple improvements in the hardware and software to address issues and lessons learned identified in the preceding units. The VIIRS sensor was designed to collect radiometric and imaging data in twenty two (22) spectral bands covering the visible and infrared spectral region between 0.4 and 12.6 microns. They operate in a polar, sun-synchronous orbit with a nominal altitude of 828 km at an inclination angle of approximately 98 degrees relative to the equator, viewing the Earth at 1:30 PM local equatorial crossing time in the ascending node. The moderate resolution bands (M-bands) and imaging resolution bands (I-bands) have a spatial resolution of 750 m and 375 m respectively, while the ground swath is 3040 km. This paper will provide an overview of the three VIIRS (SNPP, J1 and J2) sensors' performance assessments, derived using pre-launch testing under ambient and thermal vacuum environments. These sensor characterization and calibration estimates were completed by the independent government team, to verify compliance with sensor requirements, and to generate a set of metrics needed for on-orbit calibration/operations and sensor performance simulations. Key instrument performance metrics from the science and climate research perspective will be presented and discussed such as the sensor signal to noise ratios, radiance dynamic range, reflective and emissive bands calibration accuracies, polarization sensitivity, bands spectral performance, response versus scan-angle, and scattered light response. Comparison between VIIRS instruments based on pre-launch performance estimates will be included, showing areas where each instrument exhibited unexpected performance and how these issues were mitigated to ensure good quality data products.