STAR ICVS Long-Term Monitoring
The quality of satellite radiances is essential for direct radiance assimilation in numerical weather prediction, for retrievals of various geophysical parameters, and for climate trending studies. It is also a measure of the success of the engineering and science efforts of our operational satellite program. However, past efforts in post launch calibration/validation took a piecemeal approach, focusing on onboard calibration, with much less attention paid to the quality of radiance data of earth observations. Many instrument related artifacts were left to the users to discover, and evaluate the impacts. The lack of on-orbit calibration standard and methodology for radiance verification also aggravated the problem. In order to meet the challenge of the increasing demand for better satellite data quality, an integrated system that incorporates prelaunch, postlaunch onboard and vicarious, and longterm monitoring, as well as forward calculation of radiance is needed.
The core components of the integrated system include:
- On-orbit and prelaunch instrument characterization and long-term monitoring of instrument performance;
- Intersatellite calibration of radiances using the simultaneous nadir overpass (SNO) and simultaneous conical overpass (SCO) methods;
- Forward calculation of radiances using state-of-the-science radiative transfer models and in situ atmospheric profiles for validation and resolving spectral response related biases;
- On-orbit spectral calibration using hyperspectral data and atmospheric absorption features;
- Intra-satellite calibration, or calibration between instruments on the same satellite, and inter-channel calibration;
- Vicarious calibration at selected sites and using atmosphere for instrument scan asymmetry characterization; and
- Cross platform calibration from POES to NPOESS, GOES, and GOES-R. This integrated system will bring together all operational satellite radiometers and make the radiances highly traceable among a constellation of global satellites in both polar and geostationary orbits, and will become an essential tool for the implementation of GOESS.