Abstract
The CERES project relies on the MODIS and VIIRS sensors for cloud retrievals to convert the CERES observed radiances into fluxes. In order to produce climate quality data records, the cloud properties derived from the MODIS instruments onboard Terra and Aqua as well as from the VIIRS instruments onboard NPP and JPSS-1 must be consistent. Although MODIS and VIIRS have onboard solar diffusers to actively monitor inflight calibration, the absolute radiometric calibration may still differ between them, which could cause discontinuities between sensor records. The projected plan for the JPSS constellation is to maintain two operational satellites, which are spaced 45 minutes apart in the same 1:30 PM sun-synchronous orbit. The projected orbital configuration will provide no simultaneous nadir orbit (SNO) inter-calibration opportunities between any of the two operational VIIRS sensors. VIIRS inter-calibration approaches must then rely on Earth invariant or lunar targets.
This presentation will demonstrate the use Libya-4, Dome-C, and deep convective cloud (DCC) Earth invariant targets to radiometrically scale the spectrally matching visible channels of VIIRS to MODIS. The new 3rd generation geostationary (GEO) satellites, such as GOES-16 and Himawari-8, have multiple visible bands that are spectrally similar to those of MODIS and VIIRS. A double-difference technique of inter-calibration will be presented using GOES-16 and Himawari-8 as transfer radiometers. We will also present all-sky tropical ocean (ATO) and DCC ray-matching approaches that use coincident, co-angled, and co-located MODIS and VIIRS instantaneous radiances for inter-calibration. The ATO method captures the complete earth observed radiance range and will be used to validate the Earth invariant target and GEO transfer radiometer methods. Consistency between all of the independent MODIS to VIIRS inter-calibration approaches validates all approaches.
Absolute Radiometric Inter-calibration between MODIS and VIIRS Reflective Solar Bands without the use of Simultaneous Observations
The CERES project relies on the MODIS and VIIRS sensors for cloud retrievals to convert the CERES observed radiances into fluxes. In order to produce climate quality data records, the cloud properties derived from the MODIS instruments onboard Terra and Aqua as well as from the VIIRS instruments onboard NPP and JPSS-1 must be consistent. Although MODIS and VIIRS have onboard solar diffusers to actively monitor inflight calibration, the absolute radiometric calibration may still differ between them, which could cause discontinuities between sensor records. The projected plan for the JPSS constellation is to maintain two operational satellites, which are spaced 45 minutes apart in the same 1:30 PM sun-synchronous orbit. The projected orbital configuration will provide no simultaneous nadir orbit (SNO) inter-calibration opportunities between any of the two operational VIIRS sensors. VIIRS inter-calibration approaches must then rely on Earth invariant or lunar targets.
This presentation will demonstrate the use Libya-4, Dome-C, and deep convective cloud (DCC) Earth invariant targets to radiometrically scale the spectrally matching visible channels of VIIRS to MODIS. The new 3rd generation geostationary (GEO) satellites, such as GOES-16 and Himawari-8, have multiple visible bands that are spectrally similar to those of MODIS and VIIRS. A double-difference technique of inter-calibration will be presented using GOES-16 and Himawari-8 as transfer radiometers. We will also present all-sky tropical ocean (ATO) and DCC ray-matching approaches that use coincident, co-angled, and co-located MODIS and VIIRS instantaneous radiances for inter-calibration. The ATO method captures the complete earth observed radiance range and will be used to validate the Earth invariant target and GEO transfer radiometer methods. Consistency between all of the independent MODIS to VIIRS inter-calibration approaches validates all approaches.