Physical modeling of NOAA-20 VIIRS solar diffuser stability monitor sun view screen transmittance

Xi Shao; Taeyoung Choi; Changyong Cao; Tung-Chang Liu; Slawomir Blonski; Sirish Uprety; Bin Zhang

doi:10.1117/12.2528460

9 September 2019 Physical modeling of NOAA-20 VIIRS solar diffuser stability monitor sun view screen transmittance

Xi Shao, Taeyoung Choi, Changyong Cao, Tung-Chang Liu, Slawomir Blonski, Sirish Uprety, Bin Zhang

Proceedings Volume 11127, Earth Observing Systems XXIV; 111271R (2019) https://doi.org/10.1117/12.2528460
Event: SPIE Optical Engineering + Applications, 2019, San Diego, California, United States

Abstract

The Visible Infrared Imaging Radiometer Suite (VIIRS) onboard NOAA-20 satellite is designed with an onboard calibration system, including a solar diffuser (SD) and a SD stability monitor (SDSM) to monitor and maintain the radiometric quality of the calibrated Reflective Solar Band (RSB) data products. Comparison between pre-launch SDSM Sun view transmittance and the transmittance derived from post-launch yaw-maneuver data showed noticeable differences, which result in large uncertainty in the SD reflectance characterization. In particular, there were large oscillations in the SD reflectance trending due to the under-sampling of the angular variation of the SDSM Sun view transmittance using the yaw-maneuver data alone. This paper develops a physical model to simulate the NOAA-20 VIIRS SDSM Sun view transmittance. The dependences of the VIIRS SDSM Sun view transmittance on the pinhole diameter and spacing, Sun view screen thickness, and the orientation between the aperture stop and the Sun view screen are studied. The modeled SDSM Sun view transmittance is compared with that derived from the combined regular SDSM data and the yaw maneuver data. The origin of the post-launch oscillatory spikes of the NOAA-20 VIIRS SDSM Sun view transmittance is traced to the Sun view screen geometry and orientation variation between the Sun view screen and the aperture stop. The simulation results help understand the impacts of the geometric variation in the SDSM optical system on the solar calibration of NOAA-20 VIIRS.

Citation Download Citation

Xi Shao, Taeyoung Choi, Changyong Cao, Tung-Chang Liu, Slawomir Blonski, Sirish Uprety, and Bin Zhang "Physical modeling of NOAA-20 VIIRS solar diffuser stability monitor sun view screen transmittance", Proc. SPIE 11127, Earth Observing Systems XXIV, 111271R (9 September 2019); https://doi.org/10.1117/12.2528460

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