Metrics for the quality of footprint-matched passive microwave measurements

In developing footprint matching schemes for the NPOESS (National Polar-orbiting Operational Satellite System) CMIS (Conical-scanning Microwave Imager Sounder) and ATMS (Advanced Technology Microwave Sounder) instruments, we have set up an array of tests for evaluating spatial weighting patterns, radiometric fidelity, and retrieval skill for composite passive microwave measurements. The purpose of the tests is two-fold. First, footprint-matching methods can be tuned to adjust both the degree of match to a target pattern and the level of composite measurement radiometric noise. Useful measures of each of these factors are needed in order to trade-off the benefits of each, complete the matching algorithm design, and run retrieval algorithms that use measurement error characteristics as a constraint. Second, environmental parameter retrieval skill depends on the quality of the footprint matching design, and we need to be able to evaluate what radiometric and spatial quality levels are optimal with respect to retrieval performance. To evaluate the diagnostic parameters, we simulated composite footprints from sensor patterns projected on a spherical-Earth from a fixed satellite altitude. Spatial quality metrics include measures of fit to the target pattern, 3dB contour size, side-lobe level, proportional weight within the 3dB contour, and weight beyond specified linear boundaries (e.g., X km from center)