Juno Magnetic Field Investigation - Instruments
The magnetometer instruments will measure the magnetic properties
of Jupiter. On Earth, a magnetic field surrounds the planet. The
magnetism results from electric currents circulating in the molten
iron churning slowly in the Earth's core. Jupiter has a stronger
global magnetic field than Earth. Magnetic fields are usually
measured in units of "gamma", for our purposes we use the equivalent
The Advanced Stellar Compass (ASC) will provide accurate information
about the Juno spacecraft pointing for precise mapping.
Unlike the other instruments, the magnetometer sensors and ASC will
not be attached to the main body of the spacecraft. Instead, the
sensors will sit at the end of one of the three solar panels. This
placement ensures that the data generated from the magnetometer
sensors will not be "polluted" by magnetic signals from the
The fluxgate magnetometers (FGM) for the Juno mission are
based on similar instruments developed for numerous previous missions
Voyager, Magsat, International Solar Polar mission, Giotto, Active
Magnetospheric Particle Tracer Explorers, Mars Global Surveyor, etc.).
The basic configuration consists of dual; wide-range, triaxial flux
gate sensors mounted remote from the spacecraft's body. Assuming that
this field is primarily dipolar in nature at the location of the
magnetometer sensors, the ambient field can then be analytically
determined by combining the outboard and inboard measurements.
In a magnetometer of this type, the nonlinearity of magnetization
properties for the high permeability of easily saturated ferromagnetic
alloys provides an indicator of the local field strength. The word
"fluxgate" is used to refer to the method of periodic switching of
magnetic flux in the detector.
Click on picture for larger view
The FGM is being built by NASA's Goddard Space Flight Center
in Greenbelt, Maryland, U.S.A.
Advanced Stellar Compass
The Advanced Stellar Compass (ASC) will be used to provide accurate
information about the Juno spacecraft pointing. The ASC will consist
of CCD cameras and a Data Processing Unit. It will be able
to determine direction with arc sesond accuracy.
is being built by the Technical University of Denmark