page_title: Spacecraft magnetometer
section_title: Triaxial
hierarchical_section_title: Spacecraft magnetometer / Configurations of magnetometers / Triaxial
caption_attribution_description: English: Lithospheric Magnetic Anomalies. A modeled image of Earth's magnetic field variations created as a result of science satellites like Magsat. nT = nanoteslas. The color bar indicates areas with positive and negative magnetic fields.
context_page_description: Spacecraft magnetometers are magnetometers used aboard spacecraft and satellites, mostly for scientific investigations, plus attitude sensing. Magnetometers are among the most widely used scientific instruments in exploratory and observation satellites. These instruments were instrumental in mapping the Van Allen radiation belts around Earth after its discovery by Explorer 1, and have detailed the magnetic fields of the Earth, Moon, Sun, Mars, Venus and other planets and moons. There are ongoing missions using magnetometers, including attempts to define the shape and activity of Saturn's core.
  The first spacecraft-borne magnetometer was placed on the Sputnik 3 spacecraft in 1958 and the most detailed magnetic observations of the Earth have been performed by the Magsat and Ørsted satellites. Magnetometers were taken to the Moon during the later Apollo missions. Many instruments have been used to measure the strength and direction of magnetic field lines around Earth and the solar system.
  Spacecraft magnetometers basically fall into three categories: fluxgate, search-coil and ionized gas magnetometers.
context_section_description: The Sputnik-3 had a vector fluxgate magnetometer, however because the orientation of the spacecraft could not be determined the direction vector for the magnetic field could not be determined. Three axis magnetometers were used on Luna 1, Luna 2, Pioneer Venus, Mariner 2, Venera 1, Explorer 12, Explorer 14, and Explorer 15. Explorer 33 was 'to be' the first US spacecraft to enter stable orbit around the moon was equipped with the most advanced magnetometer, a boom-mounted triaxial fluxgate (GFSC) magnetometer of the early-vector type. It had a small range but was accurate to a resolution of 0.25 nT. However, after a rocket failure it was left in a highly elliptical orbit around Earth that orbited through the  electro/magnetic tail. 
   The Pioneer 9 and Explorer 34 used a configuration similar to Explorer 33 to survey the magnetic field within Earth's solar orbit. Explorer 35 was the first of its type to enter stable orbit around the moon, this proved important because with the sensitive triaxial magnetometer on board, it was found the moon effectively had no magnetic field, no radiation belt, and solar winds directly impacted the moon. Lunar Prospector surveyed for surface magnetism around the moon (1998–99), using the triaxial (extended) magnetometers. With Apollo 12 improved magnetometers were placed on the moon as part of the Lunar Module/Apollo Lunar Surface Experiments Package
  (ALSEP). The magnetometer continued to work several months after that return module departed. As part of the Apollo 14 ALSEP, there was a portable magnetometer.
  The first use of the three axis ring-coil magnetometer was on the Apollo 16 moon mission. Subsequently, it was used on the Magsat. The MESSENGER mission has triaxial ring-coil magnetometer with a range of +/- 1000 mT and a sensitivity of 0.02 mT, still in progress, the mission is designed to get detailed information about Mercurian  magnetosphere. The first use of spherical magnetometer in three axis configuration was on the Orsted (satellite).
caption: Modeled Earth magnetic fields, data created by satellites with sensitive magnetometers
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