Suomi NPP/J1 VIIRS SDR Performance Highlights and cal/val Update

The VIIRS SDR team has been working diligently maintaining the on-orbit calibration of Suomi NPP VIIRS, addressing instrument performance issues for both Suomi NPP and J1. For Suomi NPP, this includes residual effects such as calibration biases in the reflective solar bands, as well as striping in all bands; The team devoted a great deal of effort developing mitigation for J1 VIIRS performance waivers. While overall J1 VIIRS is a near identical instrument to that on Suomi NPP, differences in spectral response functions, nonlinearity in multiple channels including the DNB may have impacts on users. The RTA mirror degradation should be resolved, as well as the sync loss and single event upset. On the other hand, there are remaining issues including saturation roll-overs in multiple bands. The polarization sensitivity of J1 VIIRS is much greater which will likely have an impact on polarization striping and ocean color/aerosol applications.

The outstanding performance of the Suomi NPP VIIRS Day/Night Band(DNB) has enables a number of new nocturnal applications under lunar illumination, as well as the detection of anthropogenic and natural low light sources. In addition, its operational use at the National Weather Service in Alaska allows the DNB to be promoted to the key product parameter (KPP) status. This also raises expectations for future VIIRS models. The large nonlinearity in DNB across aggregation zones led to the use of a non-standard aggregation mode, which resulted in image size and resolution changes across scan. The new aggregation mode options (aka OP21 and OP21/26) have been used as a mitigation strategy although artifacts in imagery are apparent. Modifications to the geolocation software code by the SDR team has been developed to accommodate the changes.

In addition, expanded validation capabilities have been developed using Suomi NPP VIIRS DNB data as proxy to monitor the response versus scan both radiometrically and in geolocation accuracy. This includes the radiometric stability monitoring using nightlight point sources such as from bridges, oil platforms, power plants, as well as flares. Time series of VIIRS observations of the point sources at different scan angles are constructed to monitor the radiometric bias and geolocation across aggregation zones. Finally, lessons learned in the straylight correction for Suomi NPP will be applied to J1 VIIRS DNB to ensure that the performance meet specifications and user expectations. This paper provides an update on the VIIRS performance on Suomi NPP and highlights the characteristics of the VIIRS on JPSS J1, as well as the newly developed cal/val capabilities by the VIIRS SDR team.