Giant Magneto Impedance (GMI) Magnetometer

What is a Magnetometer?

It is a device that measures the magnetic field. A scalar magnetometer measure the magnitude of the field. A vector magnetometer is a combination of three scalar magnetometer oriented separately on the three perpendicular axis.

What is GMI? ¹

The Giant Magneto Impedance, GMI, effect consists of a large variation of the impedance of a metallic magnetic conductor when submitted to the action of a dc magnetic field.

Its origin is related to the classical electromagnetic skin effect. When a high frequency current flows along the sample, typically elongated, it is restricted to a small thickness at its surface. This penetration depth, according to the classical theory, is inversely proportional to the conductivity and to the permeability of the sample as well as to the frequency of the ac current. Consequently, large conductivity and permeability values lead to a reduced skin depth penetration depth.

Although previously discovered, it has not been until the decade of the 90’s when GMI has been actually observed and studied in a wide spectrum of magnetic materials with relatively high electrical conductivity. The magnetic permeability of such materials can be modified by the action of a dc magnetic field in such a way that it changes the penetration depth of the skin effect. Consequently, the impedance of these materials depends on the applied dc field.

Why do want this as payload?

Usually, magnetometers are used as a part of the Attitude Determination and Control system to determine the attitude of the satellite. Other magnetometers, which are more sensitive than this, are used for making geo magnetic field measurements.

Commercially, for the above purposes flux-gate magnetometers² are used in satellites. But the GMI magnetometer which we intend to develop can provide more sensitivity while being relatively smaller, less power consuming and much lighter.

Proving the feasibility of such a magnetometer in space, would be a great achievement. It would start development of the technology for commercial use in future space missions. Since the magnetometer could be developed to have a high degree of accuracy with a simple design, they could be used for very high precision measurement of the Earth’s Magnetic field. Such high precision measurements are very important for the scientific study of the Geomagnetic Field.

Note:

A prototype of a GMI Magnetometer has been developed in our institute by Ms. Sandhya with Prof. G.Markendeyulu of Physics Department.

What do we do from here?

·         Design the magnetometer which works completely on ground with an attached data processing system.

·         Find a suitable shielding method/ algorithm to do noise free magnetic field measurement from the satellite.

·         Space –qualify the magnetometer.

·         Perform the space-qualification Tests and Calibration.

·         Integrate it with the satellite and other subsystems

As a first step, a prototype of the basic instrument will be reconstructed in our institute.

This payload requires us to develop a completely new instrument from scratch. Enthusiasm in physics and electronics, a desire to constantly improve, an urge to push the skills of engineering and patience to persevere will be an added boost for its development.  

¹ Read more at http://esm.neel.cnrs.fr/2007-cluj/abs/Vazquez-abs.pdf

² Read more at http://en.wikipedia.org/wiki/Magnetometer