Optimal Magnetic Cleanliness Modeling of Spacecraft

Abstract

The magnetometers used by spacecraft for scientific research in the near-Earth and interplanetary space are highly sensitive. Since spacecraft contain in general some more or less magnetic parts which can impair scientific measurements, stringent magnetic cleanliness requirements have to be imposed on the spacecraft. In the domain of constant magnetics (magnetostatics), which is part of EMC (electromagnetic compatibility), modeling is a key issue for the verification of the magnetic cleanliness requirements. The paper describes the concept, improvements, and extensions of the multiple magnetic dipole modeling (MDM) method which had been introduced by the author in 1977 and which then has been used by numerous international scientific spacecraft projects during more than three decades. Specific issues, like the NLP method chosen and like the problem of the ambiguity of solutions, are presented in detail. Special techniques for the handling of model parameter constraints, for optimal MDM sizing, for avoidance of relative minima, and for multiple-point far-field compensation are presented as well. The extension of the MDM method to field gradient measurements is formulated and demonstrated by a significant example. Some challenging applications of MDM to spacecraft provide insight in practical modeling problems. Finally, a short description of the MDM software used is given.