Nonlinear Estimation to Assimilate GPS TEC Data into a Regional Ionosphere Model

and applications, remote sensing, spacecraft attitude and orbit determination, and general estimation, filtering, and detection. Gary S. Bust is a senior scientist in the Geospace and Earth Science Group. He received a Ph.D. in Physics from the University of Texas at Austin. His areas of interest include ionospheric tomographic imaging, data assimilation, and the application of space based observations to ionospheric remote sensing. Cathryn N. Mitchell is a professor in the Dept. of Elec-tronic and Electrical Engineering. She received a Ph.D. i