On determining fluxgate magnetometer spin axis offsets from mirror mode observations
In-flight calibration of fluxgate magnetometers that are mounted on spacecraft involves finding their outputs in vanishing ambient fields, the so-called magnetometer offsets. If the spacecraft is spin-stabilized, then the spin plane components of these offsets can be relatively easily determined...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-09-01
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| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/34/759/2016/angeo-34-759-2016.pdf |
| Summary: | In-flight calibration of fluxgate magnetometers that are mounted on
spacecraft involves finding their outputs in vanishing ambient fields, the
so-called magnetometer offsets. If the spacecraft is spin-stabilized, then
the spin plane components of these offsets can be relatively easily
determined, as they modify the spin tone content in the de-spun magnetic
field data. The spin axis offset, however, is more difficult to determine.
Therefore, usually Alfvénic fluctuations in the solar wind are used. We
propose a novel method to determine the spin axis offset: the mirror mode
method. The method is based on the assumption that mirror mode fluctuations
are nearly compressible such that the maximum variance direction is aligned
to the mean magnetic field. Mirror mode fluctuations are typically found in
the Earth's magnetosheath region. We introduce the method and provide a first
estimate of its accuracy based on magnetosheath observations by the THEMIS-C
spacecraft. We find that 20 h of magnetosheath measurements may already be
sufficient to obtain high-accuracy spin axis offsets with uncertainties on
the order of a few tenths of a nanotesla, if offset stability can be assumed. |
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| ISSN: | 0992-7689 1432-0576 |