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.