Lunar Prospector Magnetometer (MAG)

Description

The Lunar Prospector Magnetometer (MAG) will be used primarily to map the locations and strengths of the weak lunar crustal magnetic fields. There is no global lunar magnetic field, but regional crustal magnetic fields do exist. These may be paleomagnetic remnants of a former global magnetic field, or may be due to meteor impacts or other local phenomena. The scientific objectives of the experiment are to use this information to investigate the nature and origin of the Moon's magnetic field. The experiment also may allow estimates of the size and composition of the lunar core and provide information on the lunar induced magnetic dipole.

The magnetometer is housed in an 11 x 6.5 x 9 cm box located on the end of one of the three radial Lunar Prospector booms, on a 0.8 meter pole extending from the electron reflectometer. It is 2.6 meters from the Lunar Prospector in order to isolate it from spacecraft generated magnetic fields. The sensor is a triaxial fluxgate magnetometer utilizing ring-core geometry and molybdenum-permalloy magnets, similar in design to the instrument used on Mars Global Surveyor with changes made to account for the spinning spacecraft. It can measure over a range of +/- 65536 nanoTesla (nT) with a sensitivity as low as 0.002 nT and 0.006 nT RMS noise. The magnetometer data are sampled 16 times a second and compressed by delta-modulation to 6-bits per axis per channel. Occasional full samples (12 bits per axis plus range) are collected. The MAG will measure the magnetic field amplitude and direction at spacecraft altitude with a spatial resolution of about 100 km when ambient plasma disturbances are minimal. Nominal operating temperature is maintained by a combination of thermal blankets and heaters. The magnetometer and electron reflectometer instruments share a common electronics box, have a combined mass of 5 kg and use 4.5 watts of power.