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Image courtesy of Lockheed Martin

The magnetic fields measured by the MAG will be a combination of the Earth's magnetic field (35,000 nano Teslas), the field carried from the Sun by the solar wind (approximately 10 nano Teslas), and the Moon's field, which is extremely weak (approximately 1,000 nano Teslas) compared to that of the Earth. The magnetic field at the lunar surface is also affected by local deposits of magnetic material. The instruments are copies of detectors that are on board the Mars Global Surveyor spacecraft, launched in December 1996, with some modifications to adapt them for a spinning spacecraft. The triaxial fluxgate magnetometer is a standard device that is also used to measure magnetic fields on Earth. "Triaxial" means that it includes sensors to measure the strength of the field in three different directions. This enables scientists to determine not only the maximum strength of the field but also the direction it points.

The "fluxgate" is an electric coil through which the magnetic field passes. By measuring the variation of the current passing through the coil, the MAG determines the strength of the magnetic field. It can measure magnetic fields as weak as one-millionth of the strength of the Earth's magnetic field.

* The Magnetometer is mounted on a boom 8.5 feet (2.6 meters) away from the spacecraft, in order to isolate it from the magnetic fields generated by the spacecraft's own electronics.

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