Newtonian-noise cancellation in full-tensor gravitational-wave detectors

Terrestrial gravity noise, also known as Newtonian noise, produced by ambient seismic and infrasound fields will pose one of the main sensitivity limitations in low-frequency, ground-based, gravitational-wave (GW) detectors. It is estimated that this noise foreground needs to be suppressed by about 3-5 orders of magnitude in the frequency band 10 mHz to 1 Hz, which will be extremely challenging. In this article, we present a new approach that greatly facilitates cancellation of gravity noise in full-tensor GW detectors. The method uses optimal combinations of tensor channels and environmental sensors such as seismometers and microphones to reduce gravity noise. It makes explicit use of the direction of propagation of a GW and can, therefore, either be implemented in directional searches for GWs or in observations of known sources. We show that by using the extra strain channels in full-tensor GW detectors and a modest number of environmental sensors, the Newtonian-noise foreground can be reduced by a few orders of magnitude independent of the GW direction of propagation.