Development of fluxgate magnetometers and applications to the space science missions

Abstract

Magnetic field is one of the essential physical parameters to study the space physics and evolution of the solar system. There are several methods to measure the magnetic field in the space by spacecraft and rockets. Fluxgate magnetometer has been most generally used out of them because it measures the vector field accurately and does not need much weight and power budgets. When we try more difficult missions such as multi-satellite observation, landing on the celestial body and exploration in the area of severe environment, we have to modify the magnetometer or develop new techniques to make the instrument adequate for those projects. For example, we developed a 20-bit delta-sigma analogue-to-digital converter for MGF-I on the BepiColombo MMO satellite, to achieve the wide-range (±2000 nT) measurement with good resolution in the high radiation environment. For further future missions, we have examined the digitalizing of the circuit, which has much potential to drastically reduce the instrument weight, power consumption and performance dependence on the temperature. Key words: Magnetometer, magnetic field, space science. Magnet Fields in the SpaceThe magnetic fields in the space are classified into three types according to the generation sources. One is the field having the source inside or on the surface of celestial body, e.g., the Sun, planets and satellites in the solar system. In the cases of the Earth, Mercury and outer planets than Mars, magnetic dynamo is working in the liquid core, and the magnetic moment is placed at the center of the planets. The area where the magnetic field is effective spreads in the range of the planetary scale and is called "magnetosphere". Meanwhile the Moon and Mars do not have significant magnetic moment. There are weakly "magnetized" parts on the surface.The second category is the magnetic field caused by the electric current carried by plasma. For example, in the Earth's magnetosphere, magnetic field lines coming from the Antarctic region or going to the Arctic region are extended in the night direction. This configuration is represented by the summation of the magnetic fields generated by the Earth's intrinsic moment and the field along the SunEarth direction. The latter field is maintained by the electric current flowing from dawn to dusk in the plasmasheet.The third is the inductive field. One of the Maxwell's equation, rotE = −(∂B)/(∂t), represents that the rotation of the electric field is accompanied by the temporal change of the magnetic field.The time scale of the magnetic fields having the source inside or on the surface of the planets is substantially long, although they are not perfectly constant. The polarity of the earth magnetic dipole is known to have changed on the time scale of million years. The magnetic fields generated by the Copyright c TERRAPUB, 2013. electrical currents vary on the relatively short time scale, although the frequency and amplitude depend on the source phenomena. The time and spatial scales of the inductive fields, those are often ob...

Investigation of wireless magnetometer in sensing magnetic field changes at different car direction and speed

“…The current system detects Z-field in a 3-axis measurement in comparison to the 2-axis measurement which was based on the Yfield detection [1,3]. The magnetic fields spread out in an omnidirectional manner [14]. The typical characteristic of the magnetic wavelets is either having single or two positive peaks and a negative dip when a ferrous magnetic material passed over the magnetometer.…”

“…A magnetometer is an electronic device which could measure local earth magnetic field direction in space. There are several types of magnetometer such as fluxgate, magneto-inductive, and magneto-inductive [10][11][12][13][14][15]. The magnetometer applies a passive sensing technology to sense large ferrous objects.…”

The BepiColombo–Mio Magnetometer en Route to Mercury

“…A radiation-tolerant delta-sigma ADC circuit has been developed for MGF-I to perform the measurements with a resolution of 20 bits and a sampling rate of 128 Hz. Detailed electronics design and block diagrams for MGF-I are given in and Matsuoka et al (2013).…”

The ARASE (ERG) magnetic field investigation

“…The analogtype magnetometer follows the basic design adopted for many space missions (Gordon and Brown 1972;Fukunishi et al 1990;Kokubun et al 1994;Yamamoto and Matsuoka 1998;Tsunakawa et al 2010). Nevertheless, some elements of the sensor and electronics were newly developed to withstand the harsh radiation environment of Mercury (Matsuoka et al 2013). These elements are appropriate for the Arase spacecraft, which is also exposed to severe radiation.…”