  We report the improved test of frame-dragging, an intriguing phenomenon
predicted by Einstein's General Relativity, obtained using 7 years of Satellite
Laser Ranging (SLR) data of the satellite LARES (ASI, 2012) and 26 years of SLR
data of LAGEOS (NASA, 1976) and LAGEOS 2 (ASI and NASA, 1992). We used the
static part and temporal variations of the Earth gravity field obtained by the
space geodesy mission GRACE (NASA and DLR) and in particular the static Earth's
gravity field model GGM05S augmented by a model for the 7-day temporal
variations of the lowest degree Earth spherical harmonics. We used the orbital
estimator GEODYN (NASA). We measured frame-dragging to be equal to 0.9910 +/-
0.02, where 1 is the theoretical prediction of General Relativity normalized to
its frame-dragging value and +/- 0.02 is the estimated systematic error due to
modelling errors in the orbital perturbations, mainly due to the errors in the
Earth's gravity field determination. Therefore, our measurement confirms the
prediction of General Relativity for frame-dragging with a few percent
uncertainty.
