Spacecraft and interplanetary contributions to the magnetic environment on-board LISA Pathfinder

Abstract

LISA Pathfinder (LPF) has been a space-based mission designed to test new technologies that will be required for a gravitational wave observatory in space. Magnetically driven forces play a key role in the instrument sensitivity in the low-frequency regime (mHz and below), the measurement band of interest for a space-based observatory. The magnetic field can couple to the magnetic susceptibility and remanent magnetic moment from the test masses and disturb them from their geodesic movement. LISA Pathfinder carried on-board a dedicated magnetic measurement subsystem with noise levels of 10 nT Hz −1/2 from 1 Hz down to 1 mHz. In this paper we report on the magnetic measurements throughout LISA Pathfinder operations. We characterise the magnetic environment within the spacecraft, study the time evolution of the magnetic field and its stability down to 20 µHz, where we measure values around 200 nT Hz −1/2 and identify two different frequency regimes, one related to the interplanetary magnetic field and the other to the magnetic field originating inside the spacecraft. Finally, we characterise the non-stationary component of the fluctuations of the magnetic field below the mHz and relate them to the dynamics of the solar wind.

Application of LISA Gravitational Reference Sensor Hardware to Future Intersatellite Geodesy Missions

“…These are perhaps best considered as systematic error signals in competition with the Earth position-dependent gravitational "science signal", both driven by quasi-periodic orbital modulations and, thus, a dependence, or apparent dependence, on Earth position and solar exposure via the orbit. The forcingorder degrees K and Gauss variations-is orders of magnitude beyond observed field and temperature excursions in LPF [34,35], with harmonics of the roughly 0.2 mHz orbital modulations leaking into the relevant mHz band. The couplings are well understoodcoefficients ∂g ∂T and ∂g ∂∆T coupling to fluctuations in mean GRS temperature and temperature gradient [3,36], and the magnetic field gradients near the TM [34]-and mitigation is possible.…”

Transient acceleration events in LISA Pathfinder: properties and possible physical origin

“…The magnetic susceptibility of the TMs has been measured to be χ ∼ 3 × 10 −5 [27] and its permanent magnetic moment |µ| < 5 nAm 2 [28], though this is just an upper limit. The static magnetic field on board LPF was found to be |B| ∼ 1 µT [7], and, finally, from the lack of correlation between the magnetic field and force noise [29], we estimate the magnetic gradient to be less than 10 µT/m.…”

“…Besides the measurement of the TM motion, other physical quantities have been measured throughout the mission. In particular we measured: the magnetic field vector at various locations, via a dedicated set of magnetometers [7]; the temperature at various critical locations, via a dedicated set of thermistors [8]; the cosmic ray flux with a radiation monitor [9,10]; finally, two additional interferometric readouts, one monitoring frequency fluctuations (F interferometer) and the other one monitoring common mode noise sources as a reference (R interferometer) [5]. The R interferometer time series has therefore been subtracted from the ∆x, x 1 and F interferometer time series.…”

Figures of merit for a stochastic gravitational-wave background measurement by LISA: implications of LISA Pathfinder noise correlations

“…There are two types of magnetometers: the 'P ' correspond to magnetometers placed above the test masses, and the 'M ' below, following the direction z of the satellite [16]. We reconstruct the 16-day time series with a…”

“…The dark line is the LISA requirement. According to [20], the low frequency magnetic field from the interplanetary magnetic field. There is also an effect of the amplitude of the magnetic field noise with the speed of solar flare.…”