排序方式: 共有3条查询结果,搜索用时 15 毫秒
1
1.
Lohr D. A. Zanetti L. J. Anderson B. J. Potemra T. A. Hayes J. R. Gold R. E. Henshaw R. M. Mobley F. F. Holland D. B. Acuña M. H. Scheifele J. L. 《Space Science Reviews》1997,82(1-2):255-281
The primary objective of the investigation is the search for a body-wide magnetic field of the near Earth asteroid Eros. The Near Earth Asteroid Rendezvous (NEAR) 3-axis fluxgate magnetometer includes a sensor mounted on the high-gain antenna feed structure. The NEAR Magnetic Facility Instrument (MFI) is a joint hardware effort between GSFC and APL. The design and magnetics approach achieved by the NEAR MFI effort entailed low-cost, up-front attention to engineering solutions which did not impact the schedule. The goal of the magnetometer is reliable magnetic field measurements within 5 nT, which necessitates the use of an extensive spacecraft magnetic interference model but is achievable with the full year's orbital data set. Such a goal has been shown viable with recent in-flight calibration data and comparisons to the WIND magnetometer data. The NEAR MFI effort has succeeded in providing magnetic field measurements for the first flight in NASA's Discovery line. 相似文献
2.
Gold R.E. Krimigis S.M. Hawkins S.E. Haggerty D.K. Lohr D.A. Fiore E. Armstrong T.P. Holland G. Lanzerotti L.J. 《Space Science Reviews》1998,86(1-4):541-562
The Electron, Proton, and Alpha Monitor (EPAM) is designed to make measurements of ions and electrons over a broad range of
energy and intensity. Through five separate solid-state detector telescopes oriented so as to provide nearly full coverage
of the unit-sphere, EPAM can uniquely distinguish ions (Ei≳50 keV) and electrons (Ee≳40 keV) providing the context for the
measurements of the high sensitivity instruments on ACE. Using a ΔE×E telescope, the instrument can determine ion elemental
abundances (E≳0.5 MeV nucl−1). The large angular coverage and high time resolution will serve to alert the other instruments
on ACE of interesting anisotropic events. The experiment is controlled by a microprocessor-based data system, and the entire
instrument has been reconfigured from the HI-SCALE instrument on the Ulysses spacecraft. Inflight calibration is achieved
using a variety of radioactive sources mounted on the reclosable telescope covers. Besides the coarse (8 channel) ion and
(4 channel) electron energy spectra, the instrument is also capable of providing energy spectra with 32 logarithmically spaced
channels using a pulse-height-analyzer. The instrument, along with its mounting bracket and radiators weighs 11.8 kg and uses
about 4.0 W of power. To demonstrate some of the capabilities of the instrument, some initial performance data are included
from a solar energetic particle event in November 1997.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
3.
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
1