Abstract-We summarize a laser-ranged satellite test of frame dragging, a prediction of General Relativity, and then concentrate on the estimate of thermal thrust, an important perturbation affecting the accuracy of the test. The frame dragging study analysed 3.5 years of data from the LARES satellite and a longer period of time for the two LAGEOS satellites. Using the gravity field GGM05S obtained via the Grace mission, which measures the Earth's gravitational field, the prediction of General Relativity is confirmed with a 1-σ formal error of 0.002, and a systematic error of 0.05. The result for the value of the frame dragging around the Earth is µ = 0.994, compared to µ = 1 predicted by General Relativity. The thermal force model assumes heat flow from the sun (visual) and from Earth (IR) to the satellite core and to the fused silica reflectors on the satellite, and reradiation into space. For a roughly current epoch (days 1460 − 1580 after launch) we calculate an average along track drag of −0.50pm/sec 2 .I. DRAGGING OF INERTIAL FRAMES In 1918, Lense and Thirring [1] described the framedragging of an orbiting body, in the limiting case valid around Earth of slow rotation of the central body and weak gravitational field:Ω = 2J/(a 3 (1 − e 2 ) 3/2 ). Here Ω, a and e are the longitude of the ascending node, the semimajor axis and the eccentricity of the orbiting body, while J is the angular momentum of the central body. We recall that the orbital plane intersects the equator in two nodes, one of which, the ascending node, is crossed by the orbiting body from southern to northern hemisphere [2]. The Earth satisfies the conditions of "weak gravitational field" and "slowly rotating", so this formula describes the behavior of Earth satellites. This Eastward precession has been observed and measured using the two LAGEOS satellites [3]- [7] and a model of the gravitational field of the Earth provided by the GRACE mission [8], [9], with improving errors to about 10%. (Satellite Laser Ranging allows range measurement with an accuracy that can reach a few millimeters [10].) The LAGEOS tests of frame-dragging were used to set limits on some string theories equivalent to Chern-Simons gravity [11]. Another satellite experiment, Gravity Probe B (GPB), was put into orbit in 2004 and verified frame dragging (via a related gyroscope precession effect) with approximately 20% accuracy [12]. Very recently, preliminary analysis of the LARES laser ranged satellite along with the two LAGEOS satellites and latest GRACE results, produced a frame dragging consistent with that predicted by GR, with estimated 5% errors [13]. We summarize the results of that analysis below and then go on to model thermally induced forces on LARES. LARES is a satellite with a spherical tungsten alloy core which carries 92 cube corner reflectors (CCRs) for laser ranging.
II. LARES FRAME-DRAGGING MISSIONThe node shift of an orbiting body is dominated by the classical Newtonian effect due to the axially symmetric components of deviations of the gravity field ...