The dual mode Vector/Scalar Helium Magnetometer (V/SHM) instrument, flown on the Cassini mission, has provided new scientific information about Saturn's magnetic field.

A CAD model of the Scalar Helium Magnetometer instrument being developed for the Juno mission to Jupiter.

Juno wrapping Jupiter in a uniform net. The first six months are shown in blue (orbits: 2-16) and second six months are shown in green orbits: (17-31).

Unseen magnetism permeates our planet and our bodies. Earth's magnetic field protects living organisms on our planet from a variety of space radiation, provides birds and microbes with queues for navigation, and of course makes our compasses point "north." Ironically, Earth's protective magnetic field traps radiation in the so-called Van Allen Belts in a manner that degrades electronics and threatens astronauts at certain orbital altitudes.

The Sun, Jupiter, and some other planets and their satellites have their own intrinsic magnetic fields, while all solid bodies in the Solar System interact with the Sun's or parent planet's magnetic fields. By measuring these fields and how they vary, scientists can learn a great deal about the unseen interiors of various bodies. Varying magnetic field directions imprinted in the rocks paralleling our mid-ocean ridges confirmed the hypothesis of continental drift. The Galileo magnetometer is largely responsible for confirming the hypothesis that Jupiter's satellite Europa has a subsurface ocean, likely with more liquid water than all of Earth's oceans combined.

Subtle measurements and accurate calibration of space-qualified magnetometers make a powerful tool for investigating planetary interiors. At the same time, the planets' own magnetic fields are the largest structures in the Solar System, except of course the Sun's, which envelopes the entire Solar System. All these fields exhibit complex interactions with the solar wind, cosmic rays and other phenomena.

People at JPL build some of the most accurate magnetometers ever flown in space, including a major portion of the instrument being prepared for the JUNO mission to Jupiter.

Scalar Helium Magnetometer

The magnetic field investigation has three goals: Mapping of the magnetic field, determining the dynamics of Jupiter's interior, and determination of the three-dimensional structure of the polar magnetosphere. To achieve these goals, the mission employs three sensors, including a Flux Gate Magnetometer, a Scalar Helium Magnetometer, and an Advanced Stellar Compass (ASC) that provides accurate information about the Juno spacecraft pointing for precise mapping.

The bottom figure at the right shows Juno wrapping Jupiter in a uniform net that enables observations that constrain Jupiter's core and characterize its dynamo. The primary science is performed within the first six hours of perijove. The first six months are shown in blue (orbits: 2-16) and second six months are shown in green orbits: (17-31). Dr. John Connerney of the NASA Goddard Space Flight Center leads the Magnetic Field Investigation