GReAT (General Relativity Accuracy Test): a free fall test of Weak Equivalence principle from stratospheric balloon altitude

Abstract. GReAT (General Relativity Accuracy Test) is a free fall experiment from stratospheric balloon altitude to test the Weak Equivalence Principle (WEP) with an accuracy of 5 x10^-15. The key components of the experiments are a very high accuracy (sensitivity close to 10^-14 g/Sqrt(Hz) in a 25-s integration time) differential acceleration detector to detect a possible violation of the WEP and the facility necessary to perform the experiment. The detector will be released to free fall inside an evacuated capsule (Einstein elevator) which has been previously dropped from a stratospheric balloon, and will be slowly rotated about a horizontal axis to modulate the gravity signal and then released inside the capsule, immediately after the capsule’s release from the balloon. In this paper, we report the progress in the development of the dierential accelerometer that must be able to test the WEP with the declared accuracy. Following a brief description of the overall experiment, we present experimental results obtained with a dierential accelerometer prototype, in particular the ability of the sensor to reject common–mode noise components. Finally, we present a new configuration of the dierential accelerometer which is less sensitive to higher–order mass moments generated by nearby masses.