During the last ten years magnetoresistive sensor design was improved by several new technologies which make it possible to measure even weak magnetic fields. This makes them interesting for all kinds of geophysical applications where other sensor types are used today:
Investigation of the interplanetary magnetic fields. Most of the interplanetary spacecrafts investigating the solar system today carry flux gate magnetometers today which measure the solar magnetic field and its interaction with planetary fields. The fields to be measured are in the range of 0.1-40 nT.
Planetary magnetic fields. Not all planets do have a strong internal magnetic dipole field (as the earth has due to the dynamo effect). Passages of the Voyager spacecrafts have shown that Mars has no such dipole field which means that it's dynamo seems not to be active today. Landing stations as the Viking Landers in the 1970ies and Mars Pathfinder in 1997 as well as the Global Surveyor Mission starting in 1998 gave strong hints on remanent magnetic effects which come from magnetized stones on the planetary surface. Small landing missions didn't have magnetometers onboard so far; sensor size is the most important parameter for this task. Up to now fluxgate sensors are the standard parts in this application.
Earth's magnetic field. Electromagnetical exploration techniques use induced variations in the earth's magnetic field or that one of a controlled source due to resistivity variations in the ground to build up models of the ground structure. Applications are found in science as well as in commerical search for minerals and oil. The preferred sensor is the search coil today.
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Last modified: 2005-04-12 20:10:59