Detecting Bistatically Reflected GPS Signals from Low Earth Orbit Over Land Surfaces

In recent years, it has been demonstrated that bistatically reflected GPS signals from land surfaces can be used for sensing near surface soil moisture and identifying terrain features. Previous experiments were realized using near Earth platforms and the feasibility of this technique in low Earth orbit was until recently uncertain. However, using the GPS bistatic radar experiment on board the low Earth orbiting UK-DMC satellite, it is possible to examine Earth reflected GPS signals and analyze the possibility of using them for remote sensing. Earth scattered signals are being regularly detected off a wide range of surfaces with the UK-DMC experiement, including the ocean, sea ice, and land. This paper will undertake a closer examination of the UK-DMC data collected over varied land surfaces. Several Earth reflected signals will be examined with respect to detailed maps of the terrain around the bistatic reflection point. In this way the received signal power fluctuations with respect to terrain features can be observed, such as over rivers and urban areas. The relatively high received power levels of the Earth reflected GPS signals may permit using them for remotely sensing the surface. This paper is indented to present possibilities and encourage researchers to consider this technology as a viable alternative. Planned validation experiments will be discussed that are designed to determine the surface measurements capable using this low-cost technique and how they could benefit the scientific community.