The role of laser determined orbits in geodesy and geophysics

Abstract

Since the US National Aeronautics and Space Administration (NASA) launch of the LAGEOS (LAser GEOdynamics Satellite) in May of 1976, a wealth of information enhancing the knowledge of geodesy and geophysics has become available to the scientific community. Both the quality and quantity of data have improved. The precision of satellite laser ranging (SLR) is now at the sub-centimeter level, and cooperation with other nations in the purchase and deployment of SLR systems and laser satellites has led to an extensive SLR data base. Scientists are now able to make precise estimates of the product of the gravitational constant and the Earth's mass (GM), polar motion, Earth rotation, laser station coordinates, distances between stations, and tectonic plate motions. SLR also contributes strongly to improved estimates of the Earth's gravitational field. Recent NASA solutions using the laser ranging data indicate the value of GM is 398600.4408 ± 0.0006 km 3/s 2. The one sigma precision of the other geodetic parameters obtained are on average 1.9 marc sec polar motion, 0.09 ms length of day, 35 mm center of mass geodetic positioning, 20 mm baselines, and 5 mm/yr tectonic plate rates. The precision of a number of these quantities has been confirmed by comparison of an independent data set obtained by very long baseline interferometry antennas located near several of the SLR sites.