Kalman filter estimation of plasmaspheric total electron content using GPS

Abstract

We extend a Kalman filter technique for GPS total electron content (TEC) estimation by explicitly accounting for the contribution to the line‐of‐sight TEC from the plasmasphere. The plasmaspheric contribution is determined by integrating the electron density predicted by the Carpenter‐Anderson model along GPS raypaths and allowing the Kalman filter to scale the results to fit the observations. The filter also estimates the coefficients of a local fit to the ionospheric TEC and the receiver and satellite instrumental biases. We compare algorithm results with and without the plasmasphere term for three GPS receivers located at different latitudes. We validate the approach by comparing ionospheric TEC estimates with Advanced Research Projects Agency Long‐range Tracking and Instrumentation Radar measurements along coincident lines of sight to calibration objects in low Earth orbit. We find the technique is effective at separating the ionospheric and plasmaspheric contributions to the TEC by exploiting differences in the spatial distributions of electron density, and the time scales on which they vary, in these two regions.