Measuring and modeling techniques for extremely low frequency characterization of electromagnetic field emissions in space applications

Recent and upcoming European Space Agency (ESA) programs like BepiColombo, Solar Orbiter, Jupiter ICy moons Explorer (JUICE), Solar wind Magnetosphere Ionosphere Link Explorer (SMILE) and Turbulence Heating ObserveR (THOR) need not only magnetic cleanliness of almost time-constant magnetic fields, but have even more demanding requirements on slowly time-varying magnetic fields and low frequency electric fields. The frequency spectra typically have an upper limit of several hundreds of kilohertz, while the lower limit is in the sub-milliHertz range with time periods of several hours or longer. Space missions with such challenging requirements are becoming more and more relevant for the scientific community with an important presence in the current cycle of ESA's long-term planning for space science missions which is called Cosmic Vision 2015-2025. The “magnetic suite” is typically composed by three magnetometers: a pair of fluxgate magnetometers for measuring the range from DC to some tens of hertz and a single search coil magnetometer (SCM) designed to measured AC time varying magnetic field up to some tens of kilohertz. On the other hand, the “electric sensors” include different antennas or pairs of antennas in order to cover the whole frequency range which is typically from some hertz up to 200 kHz. The aim of this work is to demonstrate at an early stage the feasibility to verify the specific low-frequency electromagnetic compatibility and magnetic cleanliness requirements, especially concerning AC electric and magnetic fields. The main objectives can be summarized as follow: - Identification of a set of possible major contributors to low frequency (LF) electromagnetic interference (EMI) and sources of magnetic fields at equipment level. 
 -Characterization of LF EMI and magnetic fields on a sub-set of previously identified major contributors using flight-representative space hardware equipment under test. 
 -Identification and characterization of major internal sources for LF EMI and magnetic field emissions at component level. 
 -Utilization of simulation and modelling tools and creation of models to predict LF EMI and magnetic field emissions as measured at equipment level from measured emissions at component level. 
 -Extension of simulation and modelling tools validated at equipment level to provide predictions at system level. 
 To sum up, the main technical objectives of the presented thesis are to develop and validate, by test, new methods and techniques for on-ground verification of low frequency electromagnetic requirements, establishing complementary tools, procedures and methodologies. This challenging activity requires a multidisciplinary approach, as different methodologies have to be investigated, such as frequency and distance scaling, noise interference, high sensitivity measurements, etc. The presented methodologies are based on rigid theoretical basis and supported by extensive modelling and simulation tools, including also commercial electromagnetic tools.