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Astrophysics, Instrumentation and Methods for Astrophysics, astro-ph.IM
Abstract:
We present a study of the tilt-to-length coupling noise during the LISA
Pathfinder mission and how it depended on the system's alignment.
Tilt-to-length coupling noise is the unwanted coupling of angular and lateral
spacecraft or test mass motion into the primary interferometric displacement
readout. It was one of the major noise sources in the LISA Pathfinder mission
and is likewise expected to be a primary noise source in LISA. We demonstrate
here that a recently derived and published analytical model describes the
dependency of the LISA Pathfinder tilt-to-length coupling noise on the
alignment of the two freely falling test masses. This was verified with the
data taken before and after the realignments performed in March (engineering
days) and June 2016, and during a two-day experiment in February 2017 (long
cross-talk experiment). The latter was performed with the explicit goal of
testing the tilt-to-length coupling noise dependency on the test mass
alignment. Using the analytical model, we show that all realignments performed
during the mission were only partially successful and explain the reasons why.
In addition to the analytical model, we computed another physical
tilt-to-length coupling model via a minimising routine making use of the long
cross-talk experiment data. A similar approach could prove useful for the LISA
mission.
