Considerations Relative to Adapting Transit Observations to Predicting Radar Range Correction.
Air Force surveys in geophysics interim rept.,
AIR FORCE GEOPHYSICS LAB HANSCOM AFB MASS
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Uncertainties in the output data of SPACE TRACK radars caused by the variability of the ionosphere may be reduced 25 to 50 percent through the use of predictions of monthly median effects supplied by AWSGWC. For some ADCOM missions this degree of correction is inadequate and a further reduction in error is necessary. This may be gained by using local measurements of ionospheric parameters, such as total electron content which may be obtained from TRANSIT satellite passes, to adapt the model ionosphere. An algorithm is proposed which uses data from sequential TRANSIT passes over a limited portion of the field of view of each ADCOM radar, to adapt the AWSGWC prediction for the entire field of view. From the available TRANSIT data, it is estimated that the rms refraction error may be reduced by a factor of 3 to 4 by this technique. The principle problem which must be addressed by an adaptive technique is the inherent temporal and spatial variability of the ionosphere. The expected day-to-day variability is about 20 to 25 percent of the monthly median over a solar cycle for stations from the equator to auroral latitudes. In using TRANSIT data to adapt a local estimate of the ionospheric refraction correction, it is suggested that 1. The adaptive techniques proposed, using TRANSIT data, should be tested against archive data. 2. Techniques using other sensors of the ionosphere, such as measurements of total electron content to synchronous satellites, should be developed and tested against archive data, and the results should be compared with the technique using TRANSIT data before a final method of correction is adapted. Author
- Military Intelligence
- Active and Passive Radar Detection and Equipment