Entire Mission Striping Assessment for SNPP, NOAA-20 and NOAA-21 VIIRS

The Visible Infrared Imaging Radiometer Suite (VIIRS) instruments aboard the Suomi NPP(SNPP),NOAA-20(N20), and NOAA-21(N21) spacecraft have successfully provided Earth image products since 2011, 2017, and 2022, respectively. VIIRS has 22 bands with resolutions of 375 m and 750 m for the imaging and moderate resolution bands, respectively, covering a spectral range of 400-12,490 nm. Among them, moderate bands(M-band) 1 to 11 and imaging bands (I-band) 1 to 3 are reflective solar bands (RSBs), and M12 toM16 and I4 and I5 are thermal emissive bands (TEB). Each M-band has 16 detectors, and each I-band has 32 detectors. M-bands (1-5, 7, and 13) have dual-gain stages to enhance the measurement dynamic range. The nonlinear responses of RSB and TEB detectors were characterized during pre-launch testing. An on-board solar diffuser tracks any linear response degradation for RSB detectors. For TEB detectors, an on-board blackbody (BB) tracks linear response change, and a scheduled BB warmup and cooldown event is used to monitor the non-linearity change. Unknown biases or uncertainty in the linear or nonlinear calibration coefficients between different detectors can cause unwanted striping in the image product. In this work, the striping is assessed for all RSB and TEB of the three VIIRS instruments on SNPP, N20, and N21.The assessment is performed using the NASA Level 1B reflectance and radiance products over the entire globe to analyze the aggregate striping and any changes over time. For each band of the three instruments, the striping assessment is performed at different signal levels to analyze their nonlinearity. The striping assessment is also performed separately for both gain stages of the dual-gain bands. The motivation of this work is to have a comprehensive understanding of VIIRS striping and its signal dependency to support calibration improvements and to reduce the striping over a broad radiance range.