Magnetics Business & Technology - May/June 2020 - 7

FEATURE ARTICLE
Magnetometer performs

The first measurements from the magnetometer reached the
ground a few days after launch, confirming to the international
science teams that it was in a good shape following a successful
deployment of the spacecraft's instrument boom.

The Espace team is responsible for the manufacturing and operations of a Search-Coil Magnetometer (SCM) that will measure
medium and high-frequency magnetic field measurement as part
of the radio and plasma wave experiment. The SCM is a threeaxis search-coil sensor that will measure the magnetic field from
10Hz to 100kHz, as well as from 10kHz to 500kHz on one of the
three axes. Its measurements are crucial for the characterization
of the turbulent heating of the solar wind.
Magnetic measurements during boom deployment on February 12.
Position of magnetometer is at MAG on illustration.
"We measure magnetic fields thousands of times smaller than
those we are familiar with on Earth," says Professor Tim Horbury
of the Department of Physics at Imperial College London. He
is principal investigator for the magnetometer. "Even currents
in electrical wires make magnetic fields far larger than what we
need to measure. That's why our sensors are on a boom, to keep
them away from all the electrical activity inside the spacecraft."
Ground controllers at the European Space Operations Centre
in Darmstadt, Germany, switched on the magnetometer's two
sensors, one near the end of the boom and the other close to the
spacecraft, about 21 hours after liftoff. The instrument recorded
data before, during and after the boom's deployment, allowing
the scientists to understand the influence of the spacecraft on
measurements in the space environment.

"The spacecraft underwent extensive testing on ground to measure its magnetic properties in a special simulation facility, but
we couldn't fully test this aspect until now, in space, because the
test equipment usually prevents us from reaching the needed
very low level of magnetic field fluctuations," adds Kretzschmar.
Next, the instruments will have to be calibrated before true
science can begin. "Until the end of April, we will be gradually
turning on the in-situ instruments and checking whether they are
working correctly," says Yannis Zouganelis, ESA's deputy project
scientist for the Solar Orbiter mission. "By the end of April, we

"The data we received shows how the magnetic field decreases
from the vicinity of the spacecraft to where the instruments are
actually deployed," added Horbury. "This is an independent
confirmation that the boom actually deployed and that the instruments will, indeed, provide accurate scientific measurements in
the future."
As the titanium/carbon-fibre boom stretched out over an overall
30-minute period almost three days after liftoff, the scientists
could observe the level of the magnetic field decrease by about
one order of magnitude. While at the beginning they saw mostly
the magnetic field of the spacecraft, at the end of the procedure,
they got the first glimpse of the significantly weaker magnetic
field in the surrounding environment.
"Measuring before, during, and after the boom deployment helps
us to identify and characterize signals that are not linked to the
solar wind, such as perturbations coming from the spacecraft
platform and other instruments," said Matthieu Kretzschmar, of
Laboratoire de Physique et Chimie de l'Environnement et de
l'Espace in Orleans, France, lead co-investigator behind another
sensor located on the boom, a high frequency magnetometer of
the Radio and Plasma Waves instrument, depicted above right.

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