Todd E. Humphreys is an assistant professor in the department of Aerospace Engineering and Engineering Mechanics at the University of Texas at Austin. He received a B.S. and M.S. in Electrical andComputer Engineering from Utah State University and a Ph.D. in Aerospace Engineering from Cornell University. His research interests are in estimation and filtering, GNSS technology, GNSS-basedstudy of the ionosphere and neutral atmosphere, and GNSS security and integrity.