Earth gravitational constant

Laser range observations taken on the near-earth satellites of Lageos (a = 1.92 e.r.), Starlette (a = 1.15 e.r.), BE-C (a = 1.18 e.r.) and Geos-3 (a = 1.13 e.r.), have been combined to determine an improved value of the geocentric gravitational constant (GM). The value of GM is 398600.61 km³/sec², based upon a speed of light, c, of 299792.5 km/sec. Using the IAG adopted value of c equalling 299792.458 km/sec scales GM to 398600.44 km³/sec². The uncertainty in this value is assessed to be ± .02 km³/sec². Determinations of GM from the data taken on these four satellites individually show variations of only .04 km³/sec² from the combined result.

The Lageos information dominated the combined solution, and gave the most consistent results in its data subset solutions. The value obtained for GM from near-earth laser ranging compares quite favorably with the most recent results of the lunar laser and interplanetary experiments.