Long‐term trends in the calibration of the cluster fluxgate magnetometer instruments
Author(s)
Alconcel, L‐N
Brown, P
Oddy, T
Carr, CM
Type
Journal Article
Abstract
The calibration parameters of the Cluster mission's fluxgate magnetometer instruments have been
determined and updated on a per‐orbit basis throughout the 24 years of the mission. Since there is no absolute field reference for vector measurements in‐flight, various spacecraft‐to‐spacecraft and instrument‐to‐instrument comparisons have been used to assess the accuracy of the measurements. Relative accuracy—consistency of the FGM measurements between spacecraft—is typically1%forfields up to 4,000nT,whichcoversmostof the key scientific regions visited by the Cluster spacecraft. Absolute accuracy is harder to quantify but may be as good as 2% over the same range. An analysis of long‐term trends in the calibration parameters shows variations on annual and mission‐length timescales, particularly for sensor offsets, while sensor gains and angles are remarkably stable. Offset variations are correlated with sensor temperature—for the Cluster 1 instrument in particular—and to a lesser extent with electronics temperature; coefficients are of the order 0.1 and 0.01 nT/ºC respectively. After correction for temperature effects, there is no clearly measurable offset drift over the mission lifetime. Statistics for all four spacecraft are presented. These data could be used to inform the design and
implementation of future missions employing fluxgate magnetometers. The spacecraft are found to be
magnetically “clean,” which allows in‐flight calibration techniques to be applied with confidence and precision,
leading to consistently high‐quality magnetic‐field data sets available through the Cluster Science Archive.
determined and updated on a per‐orbit basis throughout the 24 years of the mission. Since there is no absolute field reference for vector measurements in‐flight, various spacecraft‐to‐spacecraft and instrument‐to‐instrument comparisons have been used to assess the accuracy of the measurements. Relative accuracy—consistency of the FGM measurements between spacecraft—is typically1%forfields up to 4,000nT,whichcoversmostof the key scientific regions visited by the Cluster spacecraft. Absolute accuracy is harder to quantify but may be as good as 2% over the same range. An analysis of long‐term trends in the calibration parameters shows variations on annual and mission‐length timescales, particularly for sensor offsets, while sensor gains and angles are remarkably stable. Offset variations are correlated with sensor temperature—for the Cluster 1 instrument in particular—and to a lesser extent with electronics temperature; coefficients are of the order 0.1 and 0.01 nT/ºC respectively. After correction for temperature effects, there is no clearly measurable offset drift over the mission lifetime. Statistics for all four spacecraft are presented. These data could be used to inform the design and
implementation of future missions employing fluxgate magnetometers. The spacecraft are found to be
magnetically “clean,” which allows in‐flight calibration techniques to be applied with confidence and precision,
leading to consistently high‐quality magnetic‐field data sets available through the Cluster Science Archive.
Date Issued
2026-06-01
Date Acceptance
2026-05-08
Citation
Journal of Geophysical Research: Space Physics, 2026, 131 (6)
ISSN
2169-9380
Publisher
American Geophysical Union (AGU)
Journal / Book Title
Journal of Geophysical Research: Space Physics
Volume
131
Issue
6
Copyright Statement
© 2026. The Author(s). This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
License URL
Publication Status
Published
Article Number
e2026JA035179
Date Publish Online
2026-06-06