The 1995-99 measurements of the Lense-Thirring effect using laser-ranged satellites

In general relativity a current of mass-energy, such as a spinning body, gives rise to peculiar phenomena on bodies, particles and clocks in its vicinity, which are not predicted by the Newtonian gravitational theory; one of these phenomena is the Lense-Thirring effect on particles orbiting a spinning central body. In this paper we first review the method used to measure the Lense-Thirring effect, by analysing the orbits of the two laser-ranged satellites LAGEOS and LAGEOS II, that has provided a direct measurements of this effect; we then report on these detections of the Lense-Thirring effect, obtained by analysing the nodes of LAGEOS and LAGEOS II and the perigee of LAGEOS II with the orbital programs GEODYN-SOLVE, using the Earth gravitational models JGM-3 and EGM-96 and this new method. The first detection was obtained in 1995, the most accurate measurements were obtained in 1998 using EGM-96, with about 20-30% accuracy. Finally, we briefly review the proposed LARES experiment to measure the Lense-Thirring effect with an accuracy of about 2-3% and to provide other basic tests of general relativity and gravitation.