Abstract
Abstract. In situ measurement of the magnetic field using spaceborne instruments requires a magnetically clean platform and/or a very long boom for accommodating magnetometer sensors at a large distance from the spacecraft body. This significantly drives up the costs and the time required to build a spacecraft. Here we present an alternative sensor configuration and a technique allowing for removal of the spacecraft-generated AC disturbances from the magnetic field measurements, thus lessening the need for a magnetic cleanliness programme and allowing for shorter boom length. The final expression of the corrected data takes the form of a linear combination of the measurements from all sensors, allowing for simple onboard software implementation. The proposed technique is applied to the Service Oriented Spacecraft Magnetometer (SOSMAG) on board the Korean geostationary satellite GeoKompsat-2A (GK2A). In contrast to other missions where multi-sensor measurements were used to clean the data on the ground, the SOSMAG instrument performs the cleaning on board and transmits the corrected data in real time, as needed by space weather applications. The successful elimination of the AC disturbances originating from several sources validates the proposed cleaning technique.
Highlights
Since very early in space exploration it has been clear that the main limitation in performing accurate magnetic field measurements comes not from the instruments themselves but rather from the strong artificial magnetic fields generated by the spacecraft carrying them
It was recognized that there are three possible approaches to mitigating this problem: one could limit the electromagnetic emissions coming from the spacecraft by going through a rigorous magnetic cleaning procedure. This is a costly and complicated engineering task and introduces limitations on building and operating other onboard instruments; see, for example, Narvaez (2004) for details on the magnetic cleanliness programme for the Cassini magnetic field experiment (Dougherty et al, 2004). Another approach is to accommodate the magnetometer at a large distance from the spacecraft, usually at the end of a long boom, such as the m long Kaguya boom (Kato et al, 2010) or the m long Voyager boom (Behannon et al, 1977)
The principal-component gradiometer (PiCoG) cleaning technique is based on the fact that, while the ambient magnetic field does not change over the spacecraft scale, the magnitude of a spacecraft-generated disturbance in the magnetic field decreases with the distance to the disturbance source
Summary
Since very early in space exploration it has been clear that the main limitation in performing accurate magnetic field measurements comes not from the instruments themselves but rather from the strong artificial magnetic fields generated by the spacecraft carrying them. It was recognized that there are three possible approaches to mitigating this problem: one could limit the electromagnetic emissions coming from the spacecraft by going through a rigorous magnetic cleaning procedure This is a costly and complicated engineering task and introduces limitations on building and operating other onboard instruments; see, for example, Narvaez (2004) for details on the magnetic cleanliness programme for the Cassini magnetic field experiment (Dougherty et al, 2004). If the variation of the disturbing magnetic field is much larger than the variation of the ambient magnetic field during the time interval selected to determine the cleaning parameters, the direction of the strongest disturbance will coincide with the principal component (maximum-variance component) of the measured field, allowing application of the correction only to the affected component This is the type of magnetic disturbances which can be treated using the method described .
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