Detector-level spectral characterization of the Suomi National Polar-orbiting Partnership Visible Infrared Imaging Radiometer Suite long-wave infrared bands M15 and M16

Abstract

The Suomi National Polar-orbiting Partnership (S-NPP) Visible Infrared Imaging Radiometer Suite (VIIRS) sensor data record (SDR) product achieved validated maturity status in March 2014 after roughly two years of on-orbit characterization (S-NPP spacecraft launched on 28 October 2011). During post-launch analysis the VIIRS Sea Surface Temperature (SST) Environmental Data Record (EDR) team observed an anomalous striping pattern in the daytime SST data. Daytime SST retrievals use the two VIIRS long-wave infrared bands: M15 (10.7 μm) and M16 (11.8 μm). To assess possible root causes due to detector-level spectral response function (SRF) effects, a study was conducted to compare the radiometric response of the detector-level and operational-band averaged SRFs of VIIRS bands M15 and M16. The study used simulated hyperspectral blackbody radiance data and clear-sky ocean hyperspectral radiances under different atmospheric conditions. It was concluded that the SST product is likely impacted by small differences in detector-level SRFs and that if users require optimal radiometric performance, detector-level processing is recommended for both SDR and EDR products. Future work should investigate potential SDR product improvements through detector-level processing in support of the generation of Suomi NPP VIIRS climate quality SDRs.

Assessing the Effects of Suomi NPP VIIRS M15/M16 Detector Radiometric Stability and Relative Spectral Response Variation on Striping

“…In a previous study [4], the detector-level radiance and brightness temperature were simulated using MODTRAN [7], which is a "narrow band model" atmospheric radiative transfer with a spectral resolution of 1 cm´1 for TEB bands. In comparison, the Line-By-Line Radiative Transfer Model (LBLRTM) is a more accurate and flexible radiative transfer model that can be used over the full spectral range from the microwave to the ultraviolet, providing the foundation for many radiative transfer applications [8,9].…”

“…However, "bow tie" deletion and imaging striping occurs as a trade-off to this multi-detector arrangement that must be dealt with [1]. An anomalous striping pattern has been observed in SNPP VIIRS sea surface temperature products [2][3][4]. These striping are assumed to be caused by differences in the detector-level RSR.…”

“…The VIIRS SDR team performed studies to investigate possible root causes. Padula and Cao [4] used MODTRAN to evaluate the brightness temperature difference caused by the difference between band averaged (which is used in the operations) and detector level SRF. However, some studies [5] indicate that the forward model MODTRAN does not reproduce spectral, angular, and water vapor dependencies with accuracies acceptable for SST analyses.…”

Crosstalk Effect in SNPP VIIRS

“…The methodology has also been adopted and applied later for the RSB to reduce the striping in ocean color products [20]. The striping can be induced by various causes such as detector-dependent relative spectral response (RSR) [21][22][23], crosstalk effect [24][25][26][27][28][29][30][31], and others. For RSB, the detector dependent polarization effect is another major cause for the striping in the imagery [32,33].…”

“…For RSB, the detector dependent polarization effect is another major cause for the striping in the imagery [32,33]. The potential induction of the striping in the TEB imagery by RSR errors has been investigated and discussed [21][22][23] but has not fully explained the striping in SNPP VIIRS TEB. This examination focuses on crosstalk contaminations as a physical cause of significant striping as well as other effects in the science products.…”