ESA Science & Technology - GALILEO GALILEI (GG) Proposed Space Experiment to Test the equivalence Principle and Preliminary Results from the Prototype on the Ground

Publication date: 15 January 2000

Authors: Nobili, A.M. et al.

Page: 309-327

Proceedings of 1999 NASA/JPL International Conference on FUNDAMENTAL PHYSICS IN SPACE, April 29,30 and May 1, 1999, Washington DC, NASA Document D-18925. "GALILEO GALILEI" (GG) is a proposal for a small, low orbit satellite devoted to testing the Equivalence Principle (EP) of Galileo, Newton and Einstein. The GG Report on Phase A Study recently carried out with funding from ASI (Agenzia Spaziale Italiana) concludes that GG can test the Equivalence Principle to 1 part in 10¹⁷ at room temperature. The main novelty is to modulate the expected differential signal of an EP violation at the spin rate of the spacecraft (2 Hz). As compared to other experiments, the modulation frequency is increased by more than a factor 10⁴, thus reducing 1/f (low frequency) electronic and mechanical noise. The challenge in this field is to fly an experiment able to improve by many orders of magnitude the current best sensitivity (of about 1 part 10¹²). This requires spurious relative motions of the test bodies to be greatly reduced, leaving them essentially motionless. Doing that with more than one pair of bodies appears to be an unnecessary complication. This is why GG is now proposed with a single pair of test masses. -- Remainder of abstract truncated --