Primary emphasis is on dynamics and control with a specialization in estimation problems and Kalman filtering. Applications of primary interest include GPS/GNSS-based navigation, GPS/GNSS receivers for new signals or unusual environments, GPS/GNSS integrity, alternatives to GPS/GNSS, spacecraft orbit determination, spacecraft attitude determination & control, and remote sensing of the upper atmosphere. Efforts include the development of novel system designs/concepts, of the corresponding problem models, and of the associated numerical estimation algorithms and software. Some projects involve flight hardware and experiments or campaigns to collect remote-sensing data. Other projects are based primarily on analysis and simulation. Virtually all efforts include significant development of custom-designed numerical analysis algorithms and software.