Vertical resolution approaching 100 m for GPS occultations of the Earth's atmosphere

Vertical resolution is a fundamental aspect of any atmospheric remote sensi ng technique. Occultations using the Global Positioning System (GPS) signal s provide inherently high vertical resolution. The phase coherence of the G PS signals allows improvement beyond the resolution limit set by Fresnel di ffraction and the viewing geometry. We have characterized this improvement by simulating the forward propagation of GPS signals through the atmosphere to the GPS receiver. The signals are then back-propagated to a position cl oser to the atmosphere, thereby reducing the effects of diffraction. Compar ison between the direct and the back-propagated results indicates that the resolution is improved by a factor of several, down to similar to 100 m.