Subtraction of Newtonian Noise

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Abstract:: Often times when measuring for gravitational waves detectors pick up gravitational disturbances
from local sources (Newtonian noise). This causes a problem. Desired measurements are polluted with
this Newtonian noise (NN) and in order to view data accurately the noise must be subtracted out. At the
former Homestake mine in Lead, South Dakota seismic noise, from which NN originates, is rather low in
underground locations. Research here has several main goals, two of which are investigating how to
subtract NN from GW measurements and determining if this is done more efficiently at underground
locations or above ground ones like at Hanford, Washington and Livingston, Louisiana. Progress has
been made in both goals, but improvements, including the set up of the seismic array and how to subtract
NN with filters, are still needed. This entire operation will span over many years and during this summer
of 2010 small, but effective, modifications to the seismic array, advances in NN knowledge, and
comparison of the systems used in the array will be made. It is expected modifying geophones to sense
low frequencies will allow Hanford and Livingston to sense low frequencies which will eventually lead to
NN filters at these locations and may provide cheaper instrumentation than the seismometers used at
Homestake if it is found geophones also work well underground.

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LIGO Document T1000710-v1