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Brian J. Anderson Mario H. Acuña David A. Lohr John Scheifele Asseem Raval Haje Korth James A. Slavin 《Space Science Reviews》2007,131(1-4):417-450
The Magnetometer (MAG) on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission is a low-noise,
tri-axial, fluxgate instrument with its sensor mounted on a 3.6-m-long boom. The boom was deployed on March 8, 2005. The primary
MAG science objectives are to determine the structure of Mercury’s intrinsic magnetic field and infer its origin. Mariner
10 observations indicate a planetary moment in the range 170 to 350 nT R
M3 (where R
M is Mercury’s mean radius). The uncertainties in the dipole moment are associated with the Mariner 10 trajectory and variability
of the measured field. By orbiting Mercury, MESSENGER will significantly improve the determination of dipole and higher-order
moments. The latter are essential to understanding the thermal history of the planet. MAG has a coarse range, ±51,300 nT full
scale (1.6-nT resolution), for pre-flight testing, and a fine range, ±1,530 nT full scale (0.047-nT resolution), for Mercury
operation. A magnetic cleanliness program was followed to minimize variable and static spacecraft-generated fields at the
sensor. Observations during and after boom deployment indicate that the fixed residual field is less than a few nT at the
location of the sensor, and initial observations indicate that the variable field is below 0.05 nT at least above about 3 Hz.
Analog signals from the three axes are low-pass filtered (10-Hz cutoff) and sampled simultaneously by three 20-bit analog-to-digital
converters every 50 ms. To accommodate variable telemetry rates, MAG provides 11 output rates from 0.01 s−1 to 20 s−1. Continuous measurement of fluctuations is provided with a digital 1–10 Hz bandpass filter. This fluctuation level is used
to trigger high-time-resolution sampling in eight-minute segments to record events of interest when continuous high-rate sampling
is not possible. The MAG instrument will provide accurate characterization of the intrinsic planetary field, magnetospheric
structure, and dynamics of Mercury’s solar wind interaction. 相似文献
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