Gravitational-wave Geodesy: A New Tool for Validating Detection of the Stochastic Gravitational-wave Background

A valuable target for advanced gravitational-wave detectors is the stochastic gravitational-wave background. The stochastic background imparts a weak correlated signal into networks of gravitational-wave detectors, and so standard searches for the gravitational-wave background rely on measuring cross-correlations between pairs of widely separated detectors. Stochastic searches, however, can be affected by any other correlated effects that may also be present, including correlated frequency combs and magnetic Schumann resonances. As stochastic searches become sensitive to ever-weaker signals, it is increasingly important to develop methods to separate a true astrophysical signal from other spurious and/or terrestrial signals. Here, we describe a novel method to achieve this goal—gravitational-wave geodesy. Just as radio geodesy allows for the localization of radio telescopes, so too can observations of the gravitational-wave background be used to infer the positions and orientations of gravitational-wave detectors. By demanding that a true observation of the gravitational-wave background yield constraints that are consistent with the baseline's known geometry, we demonstrate that we can successfully validate true observations of the gravitational-wave background while rejecting spurious signals due to correlated terrestrial effects.