The purpose of the “Atom Interferometry Test of the Weak Equivalence Principle in Space” study was to conceive and specify an instrument for an atom interferometry test of the Weak Equivalence Principle (Quantum WEP test, QWEP), focusing on the International Space Station (ISS) as space platform. The study was carried out between March 2012 and May 2013 by a team led by Thales Alenia Space Italia (Torino) with the European Laboratory for Non-linear Spectroscopy (LENS, Firenze) as main partner, and the Istituto Nazionale di Fisica Nucleare (Pisa), Thales Research and Technology (Paris) and Marwan Technology (Pisa) as consultants.
QWEP is a new test of the WEP, targeting 10-14 accuracy in the Eötvös ratio, based on simultaneous measurement of the free-fall acceleration of two different atomic species, or isotopes, by an atom interferometer. A preliminary design and layout of the experiment was developed and instrument accommodation in a standard rack inside the Columbus orbital facility was studied. The required resources are well within the limits set by a Columbus payload. The environment was analysed and disturbing effects were assessed. Inertial effects (Earth gravity gradients, rotation) are the major limiting factors in the error budget. According to the error analysis, the accuracy objective appears feasible, in about 2 years of shot noise-limited measurements in the microgravity environment offered by the ISS.
The required technology is assessed to be available at TRL of 4 or better, as far as the component parts are concerned. At the system level, however, experimental demonstration does not yet exist. To assist this goal, a preliminary plan of laboratory experiments is proposed