Validation of the Gallagher Protonospheric Model

Ionospheric models are used in many systems throughout the Department of Defense: for example, they are useful in correcting range errors in radio signals. However, correction models don't incorporate the protonosphere, the torus-shaped plasma volume above the ionosphere. The Gallagher Protonospheric Model, recently incorporated into the Parameterized Ionospheric Model 1.7 (PIM 1.7), was validated against protonospheric total electron content (PTEC) measurements made by the GPS system. Gallagher model calculations of slant PTEC for Pittsburgh ground station looking south with a raypath at an elevation of 26 degrees were compared against GPS PTEC measurements for the same configuration derived from the Dual Station Technique (DST). In the DST, 11 days of GPS TEC measurements were obtained from Charleston and Pittsburgh, taking advantage of the latitudinal asymmetry of the protonosphere to obtain PTEC. The Gallagher model results were in general agreement with measured PTEC, indicating a slight diurnal change in PTEC (<2 PTEC). Groundtmth PTEC accuracy was estimated at 2-3. 5 PTEC, masking any trend measurement, yet good enough to validate the potential of Self Calibration Of Pseudo-range Errors (SCORE) and DST to measure PTEC using GPS. PIM 1.7 users should be aware of Gallagher's limits: empirical, limited to 00-10 Magnetic Local Time, and +1-40 degrees geomagnetic latitude.Air Force Inst of Tech Wright-Patterson AFB Oh School of Engineering is the author of 'Validation of the Gallagher Protonospheric Model', published 1999 under ISBN 9781423547068 and ISBN 1423547063.