Complex sentence: A main constraint on magnetometers in space is the availability of power and mass. Magnetometers fall into 3 major categories: the fluxgate type, search coil and the ionized vapor magnetometers.
Split into simpler sentences: A main constraint on magnetometers used in space is the availability of energy and weight. Magnetometers have fallen into 3 major categories: the fluxgate type, search coil and the ionized vapor magnetometers.