Magnetometers are direct-sensing instruments that detect and measure the strength of magnetic fields in the vicinity of the spacecraft. The Cassini Dual-Technique Magnetometer (MAG) measures magnetic fields during the Titan and Saturn encounters. The MAG consists of a vector/scalar helium magnetometer sensor, a fluxgate magnetometer sensor, a data processing unit, three power supplies, plus operating software and electronics associated with the sensors.
The vector/scalar helium magnetometer (V/SHM) sensor is used to make both vector (magnitude and direction) and scalar (magnitude only) measurements of magnetic fields. The V/SHM and its electronics are being supplied by JPL. The fluxgate magnetometer (FGM) sensor is used to make vector field measurements. This sensor and its electronics are being provided by the Imperial College of London.
The instrument data processing unit (DPU) is the responsibility of the Technical University of Braunschweig. The DPU interfaces with the spacecraft Command and Data Subsystem through the JPL-designed bus interface unit (BIU). All commands, data, and processor program changes are received or transmitted through the BIU. The MAG components are powered by three power supplies plus the 30-volt spacecraft bus. Power supply 0 powers the BIU and the DPU. Power supplies 1 and 2 are redundant and power the V/SHM electronics. The FGM electronics are powered by the spacecraft bus.
Since magnetometers are sensitive to electric currents and ferrous components on the spacecraft, they are generally placed on an extended boom, as far from the spacecraft as possible. In this case, the FGM sensor is located midway out on the Cassini magnetometer boom, and the V/SHM sensor is located at the end of the boom. The boom itself, composed of thin, nonmetallic rods, will be collapsed very compactly during launch and deployed only after the spacecraft has separated from the launch vehicle.