The GBAR experiment, proposing a gravity measurement of antihydrogen at the planned ELENA facility, was approved by the Research Board in May 2012. The collaboration is formed of 15 laboratories and about 50 researchers (January 2014).
The goal of GBAR is to test the Einstein Weak Equivalence Principle (WEP), which states that the trajectory of a test particle is independent of its composition and internal structure when it is only submitted to gravitational forces. This fundamental principle has never been directly tested with antimatter. GBAR will directly measure the free-fall acceleration, noted g, of neutral antihydrogen atoms in the terrestrial gravitational field.