Abstract
The Visible Infrared Imager Radiometer Suite (VIIRS) was launched last year aboard the Suomi NPP satellite. The high quality of the radiometric data can be attributed to thorough pre-launch spectral response characterization by the vendor and validation using the Spectral Irradiance and Radiance Responsivity Calibrations Using Uniform Sources (SIRCUS) facility provided by the National Institute of Standards and Technology (NIST). The GOES-R program is similarly developing an imaging radiometer, the Advanced Baseline Imager (ABI), which has six of its 16 channels in the visible and near infrared wavelength range and which roughly match six channels of VIIRS. Much like VIIRS, ABI is undergoing intensive pre-launch characterization and the spectral response functions for the first flight model are now available. This gives us a unique opportunity to make a detailed analysis of the spectral response function differences and predict the resulting biases when viewing radiances from typical targets. In addition, as an illustrative example of on-orbit performance, we take calibrated Earth scene radiances from VIIRS over a well-characterized, highly spatially uniform site to derive the top-of-atmosphere spectral radiance using radiative transfer modeling. We then use the ABI spectral response functions, along with geometric resampling to match the prescribed pixel footprint of ABI, to predict the radiometric bias between VIIRS and ABI for this particular scene. This work highlights the importance of achieving low uncertainties in spectral response functions to achieve high radiometric accuracy on orbit.
Predicting the Radiometric Biases between ABI and VIIRS Due to Spectral Response Function Differences
The Visible Infrared Imager Radiometer Suite (VIIRS) was launched last year aboard the Suomi NPP satellite. The high quality of the radiometric data can be attributed to thorough pre-launch spectral response characterization by the vendor and validation using the Spectral Irradiance and Radiance Responsivity Calibrations Using Uniform Sources (SIRCUS) facility provided by the National Institute of Standards and Technology (NIST). The GOES-R program is similarly developing an imaging radiometer, the Advanced Baseline Imager (ABI), which has six of its 16 channels in the visible and near infrared wavelength range and which roughly match six channels of VIIRS. Much like VIIRS, ABI is undergoing intensive pre-launch characterization and the spectral response functions for the first flight model are now available. This gives us a unique opportunity to make a detailed analysis of the spectral response function differences and predict the resulting biases when viewing radiances from typical targets. In addition, as an illustrative example of on-orbit performance, we take calibrated Earth scene radiances from VIIRS over a well-characterized, highly spatially uniform site to derive the top-of-atmosphere spectral radiance using radiative transfer modeling. We then use the ABI spectral response functions, along with geometric resampling to match the prescribed pixel footprint of ABI, to predict the radiometric bias between VIIRS and ABI for this particular scene. This work highlights the importance of achieving low uncertainties in spectral response functions to achieve high radiometric accuracy on orbit.