| dc.description.abstract | GNSS satellites such as GPS are playing an increasingly crucial role in tracking low earth orbiting (LEO) remote sensing satellites at altitudes below 3000 km with accuracies of better than 10 cm (Yunck et al. 1990). These remote sensing satellites employ a precise global network of GNSS, GRACE (Gravity Recovery And Climate Experiment) and Altimetry ground receivers operating in concert with receivers onboard the LEO satellites, with all estimating the satellites’ orbits, GPS orbits, and selected ground locations simultaneously (Yunck et al. 1990). In this chapter, we illustrate the role played by GNSS satellites in measuring changes in the Earth’s atmosphere, its gravity field, and surfaces (e.g., ice layer density). These changes are found by measuring refractivity, inter-satellite distances, and reflected signals (i.e., multipath), respectively. | en |
