This long, hinged magnetometer boom extended from one of the octagonal sides of the spacecraft body. The magnetic field experiment carried out by Mariner 10 consisted of two 3-axis sensors located at different positions along a 5.8-m (20-ft) boom extending from one of the octagonal sides of the body. Two sensors carried on the boom were biaxial fluxgate magnetometers. Their purpose was to permit the simultaneous measurement of the magnetic field, which is the sum of the weak magnetic field in space (and near the planets) and the magnetic field of the spacecraft itself.
NASA's Jet Propulsion manufactured and transferred this artifact to the Musuem in 1982.
Transferred from NASA - Jet Propulsion Laboratory