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Calibration Approach
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One method of calibration uses the development of a model to simulate satellite transmissions. A model has been developed entirely of software (several thousand lines of FORTRAN code) that emulates the actual operation of the Seawinds instrument. It is set up to use Level 1A telemetry data, which contains information such as the time each pulse was transmitted, the antenna position, and the satellite position, velocity, and attitude. The implementation of the model relies on the L1A data as well as exact specifications of the instrument to simulate the instrument. When the actual spacecraft passes over the CGS the transmitted microwave pulses are captured and stored; the model emulates these capture files. The actual and simulated sets are compared for differences. The comparison analyzes timing, power, and frequency to determine discrepancies between the model and the data. The model is then rerun, perturbing certain parameters until the error between the model data and CGS data is minimized. The resulting simulation parameters then match the actual data and are used to compute the system calibration.
