Identification and Removal of Reaction Wheel Interference from In-Situ
Magnetic Field Data using Multichannel Singular Spectrum Analysis
Abstract
In-situ magnetic field measurements are critical to our understanding of
a variety of space physics phenomena including field-aligned currents
and plasma waves. Unfortunately, high-fidelity magnetometer measurements
are often degraded by stray magnetic fields from the host spacecraft,
its subsystems, and other instruments. One dominant source of magnetic
interference on many missions are reaction wheels - spinning platters of
varying rates used to control spacecraft attitude. This manuscript
presents a novel approach to the mitigation of reaction wheel
interference on magnetometer measurements aboard spacecraft where
multiple magnetometer sensors are deployed. Specifically, multichannel
singular spectrum analysis is employed to decompose multiple time series
simultaneously. A technique for automatic component selection is
proposed that classifies the decomposed signals into common geophysical
signals and disparate locally generated signals enabling the robust
estimation and removal of the local interference without requiring any
assumptions about its characteristics or source. The utility of this
proposed method is demonstrated empirically using in-situ data from the
CASSIOPE/Swarm-Echo mission, and a data interval with near-constant
background field was shown to have its local reaction wheel interference
reduced from 1.90 nT RMS, for the uncorrected outboard sensor, to 0.21
nT RMS (an 89.0\% reduction). This technique can be
generalized to arrays of more than two sensors, and should apply to
additional types of magnetic interference.