Geoscience from GPS Tracking by Earth Satellites

As the Global Positioning System enters its operational phase, efforts to exploit GPS for earth science are coming into sharper focus. Some of these activities have taken new directions, away from the positioning and navigation tasks familiar to GPS users into areas of direct earth observation. Perhaps the most visible GPS earth science applications today are precise orbit determination of remote sensing satellites—primarily ocean altimetric satellites—and direct measurement of earth baselines for studies in solid earth dynamics. The mid-1980s saw the development of specialized GPS-based techniques to determine the orbits of any GPS-equipped low earth satellite with sub-decimeter accuracy [Yunck and Wu 1986; Yunck et al 1990]. These will have their first full-scale demonstration on TOPEX/POSEIDON, the joint US/ French oceanographic satellite set for launch in 1992.