Novel methods to measure the gravitational constant in space

Abstract

We present two novel methods, tested by LISA Pathfinder, to measure the gravitational constant G for the first time in space. Experiment 1 uses electrostatic suspension forces to measure a change in acceleration of a test mass due to a displaced source mass. Experiment 2 measures a change in relative acceleration between two test masses due to a slowly varying fuel tank mass. Experiment 1 gave a value of G = 6.71 ± 0.42 ( × 10 − 11 )

m 3

s − 2

kg − 1 and experiment 2 gave 6.15 ± 0.35 ( × 10 − 11 )

m 3

s − 2

kg − 1 , both consistent with each other to 1 σ and with the CODATA 2014 recommended value of 6.67408 ± 0.00031 ( × 10 − 11 )

m 3

s − 2

kg − 1 to 2 σ . We outline several ideas to improve the results for a future experiment, and we suggest that a measurement in space would isolate many terrestrial issues that could be responsible for the inconsistencies between recent measurements.