Astronomers have achieved the most accurate measurement yet of Earth's frame-dragging effect on spacetime using a compact satellite designed for laser tracking.
A team led by Ignazio Ciufolini at the Wuhan Institute of Physics and Mathematics used the LARES-2 satellite, launched in July 2022, to measure the Lense-Thirring effect with an uncertainty of just 0.2 percent. The 294.8-kilogram sphere, covered in 303 retroreflectors, flew in a supplementary orbit with the older LAGEOS satellite to cancel Newtonian perturbations from Earth's oblate shape.
Data from about 200,000 laser ranging observations between July 2022 and June 2025 yielded a drift of 61.3 milliarcseconds per year in the satellites' combined orbits, matching general relativity predictions within one to two parts per thousand. The researchers also removed the dominant K1 lunisolar tide signal by averaging over one full 1,050-day precession cycle.
Ciufolini said the result narrows the allowed parameter space for Chern-Simons gravity theories that modify Einstein's equations. The same analysis produced a refined measurement of the K1 tide strength, which could aid studies of earthquakes.
The satellites are expected to remain in orbit for centuries, allowing future observations to tighten the constraints further.
