Abstract
We report the first results of the LISA Pathfinder in-flight experiment. The results demonstrate that two free-falling reference test masses, such as those needed for a space-based gravitational wave observatory like LISA, can be put in free fall with a relative acceleration noise with a square root of the power spectral density of 5.2±0.1 fm s^{-2}/sqrt[Hz], or (0.54±0.01)×10^{-15} g/sqrt[Hz], with g the standard gravity, for frequencies between 0.7 and 20mHz. This value is lower than the LISA Pathfinder requirement by more than a factor 5 and within a factor 1.25 of the requirement for the LISA mission, and is compatible with Brownian noise from viscous damping due to the residual gas surrounding the test masses. Above 60mHz the acceleration noise is dominated by interferometer displacement readout noise at a level of (34.8±0.3) fm/sqrt[Hz], about 2 orders of magnitude better than requirements. At f≤0.5 mHz we observe a low-frequency tail that stays below 12 fm s^{-2}/sqrt[Hz] down to 0.1mHz. This performance would allow for a space-based gravitational wave observatory with a sensitivity close to what was originally foreseen for LISA.
Highlights
We report the first results of the LISA Pathfinder in-flight experiment
The results demonstrate that two free-falling reference test masses, such as those needed for a space-based gravitational wave observatory like
LISA Pathfinder [1] (LPF) is a European Space Agency mission launched on December 3, 2015 and dedicated to an end-to-end experimental demonstration of the free fall of test masses (TMs) at the level required for a future space-based gravitational wave (GW) observatory, such as LISA [2]
Summary
LISA Pathfinder [1] (LPF) is a European Space Agency mission launched on December 3, 2015 and dedicated to an end-to-end experimental demonstration of the free fall of test masses (TMs) at the level required for a future space-based gravitational wave (GW) observatory, such as LISA [2]. The best example of the results obtained to date is the noise measurement shown, with the ASD of the differential TM acceleration Δg compared to the LPF and LISA requirements. This Letter reports on the first 55 days of science operations, including a description of the differential acceleration measurements performed, the main results obtained so far, and their implications for a largescale space-based GW observatory. In-depth reports on the wealth of dedicated experiments of LPF, many of which are still being performed, will be reported in separate papers
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