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5. Test and Validation Plans

Preliminary plans have been made to validate the "instrument" data by comparing refractivity profiles derived from GPS/MET to refractivity profiles derived from gridded radiosonde data that will be obtained via the Internet from the NWS and other operational sources. For selected cases, we will compare GPS/MET derived temperature and moisture profiles to profiles derived from gridded operational data. Specific occultations will be selected for validation tests based on the availability of hi quality operational data in the area. Cases representative of polar, temperate, and tropical conditions will be tried, as well as northern and southern hemisphere cases. We will also test the validity of the data for several spacecraft/payload configurations to determine the sensitivity of various satellite operational considerations.

A sophisticated 3-D ray-tracing tool has been obtained from NOAA and modified for GPS/MET use. Using the ray-tracing tool and operational measurements of the atmosphere and ionosphere, along with orbit information, simulated GPS/MET Payload phase measurements can be derived. We will derive phase "measurements" using this tool, and compare them with coincident GPS/MET payload raw phase observations.


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