GSICS VISNIR reference imager March 16 2020 Background
GSICS VIS/NIR reference imager March 16, 2020
Background • The VIS/NIR does not have a hyper-spectral reference sensor with SI traceable calibration. • CLARREO pathfinder in 2023? • GSICS must rely on a multichannel RSB reference imager and use spectral band adjustment factors to tie the GEO imager calibration • This is based on scene type target, DCC, desert, moon, etc. • Unlike the IR, where the all of the reference IASI, Cr. IS sensors have very similar absolute BT values, the Aqua-MODIS, NPP-VIIRS and NOAA-20 VIIRS absolute calibration can differ by 1 -3% depending on channel. • Does the lunar calibration have its own independent reference? • If we have multiple VIS/NIR methods how do we tie them to the same reference? • How does it match the current MODIS and VIIRS references?
The GSICS RSB reference imager • The DCC invariant target calibration method is a stability monitoring method • The GEO records do not need to be reprocessed when changing the reference imager • The reference imager DCC response over the GEO domain will need to be performed • We started with Aqua-MODIS and were migrating to NPP-VIIRS, since the channel SRFs were more similar across all the bands • NOAA-20 also has SRFs that are similar to NPP • Should we follow the IR subgroup and have multiple products based on multiple reference imagers. • Raj could easily provide the reference imager DCC response over the individual GEO domains. • IF GSICS recommends a RSB reference imager. We are saying the best characterized, optimal on orbit performance, not necessarily the most reliable absolute calibration.
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