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 $$0.9910 \pm 0.02$$0.9910±0.02 , where 1 is the theoretical prediction of General Relativity normalized to its frame-dragging value and $$\pm 0.02$$±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.

It is estimated that today several hundred operational satellites are orbiting Earth while many more either have already reentered the atmosphere or are no longer operational. On the 13th of February 2012 one more satellite of the Italian Space Agency has been successfully launched. The main difference with respect to all other satellites is its extremely high density that makes LARES not only the densest satellite but also the densest known orbiting object in the solar system. That implies that the nongravitational perturbations on its surface will have the smallest effects on its orbit. Those design characteristics are required to perform an accurate test of frame dragging and specifically a test of Lense-Thirring effect, predicted by General Relativity. LARES satellite, although passive, with 92 laser retroreflectors on its surface, was a real engineering challenge in terms of both manufacturing and testing. Data acquisition and processing are in progress. The paper will describe the scientific objectives, the status of the experiment, the special feature of the satellite and separation system including some manufacturing issues, and the special tests performed on its retroreflectors.

In 2016, we published “A test of general relativity using the LARES and LAGEOS satellites and a GRACE Earth’s gravity model. Measurement of Ear

This work has been developed in the framework of the LARES mission of the Italian Space Agency (ASI). The LARES satellite has been built to test, with high accuracy, the frame–dragging effect predicted by the theory of General Relativity, specifically the Lense–Thirring drag of its node. LARES was the main payload in the qualification flight of the European Space Agency launcher VEGA. A concern arose about the possibility of an impact between the eight secondary payloads among themselves, with LARES and with the last stage of the launcher (AVUM). An impact would have caused failure on the payloads and the production of debris in violation of the space debris mitigation measures established internationally. As an additional contribution, this study allowed the effect of the payload release on the final manoeuvers of the AVUM to be understood.