Magnetic Ion-Mass Spectrometer (MIMS)

A magnetic ion-mass spectrometer was flown to measure in situ the concentrations of
the ambient positive ion species in the mass range from 1 to 90 atomic mass units (u). Mounted on
the satellite equator normal to the spin axis, the entrance aperture faced forward when the
spacecraft was in the despun mode. The electric and magnetic fields were arranged to produce
a mass spectrum along the focal plane following the magnetic analyzer. Three slits were placed
along this plane in appropriate places to simultaneously collect ions in the mass ratio 1-4-16.
Ionospheric ions were accelerated into the analyzer system by a negative voltage that varied
from -1060 to -225 V. The three mass ranges measured simultaneously were 1 to 4, 4 to 16,
and 14 to 72 u. Following each slit was an electron multiplier and logarithmic
electrometer-amplifier detector. The detector output was either measured directly for an analog
output, or was supplied to a "peak" circuit that determined the amplitude of each peak in the
spectrum. Only the amplitude of each peak was telemetered in the "peak" mode, and in this mode
the time required to simultaneously sweep all three mass ranges was 1 s. Other modes of
operation were possible. In the analog short mode, the three mass ranges were swept in 2 s,
alternating with 1-s "peak" mode scans. An 8-s sweep time was required in the analog long mode,
again alternating with 1-s "peak" mode scans. An option existed in the locked mode to
continuously measure any set of mass numbers in the ratio 1-4-16 to give high spatial resolution.
More experiment detail can be found in J. H. Hoffman et al., Radio Sci., v. 8, n. 4, p. 315,
1973. NSSDC has all the useful data that exist from this investigation.

一台磁离子质量光谱仪被搭载飞行，以原位测量大气正离子种类的浓度，其质量范围为1至90原子质量单位（u）。该仪器安装在卫星赤道位置，垂直于自旋轴，当航天器处于去自旋模式时，入口孔径朝向前方。电场和磁场被配置以在磁分析器后的焦平面上产生质量光谱。在该平面上适当的位置放置了三个狭缝，以同时收集质量比为1-4-16的离子。电离层离子通过从-1060至-225伏的负电压被加速进入分析系统。同时测量的三个质量范围为1至4、4至16和14至72 u。每个狭缝后面都连接有一个电子倍增器和对数电磁计放大器检测器。检测器的输出要么直接测量以获得模拟输出，要么供给一个“峰值”电路，以确定光谱中每个峰值的幅度。在“峰值”模式下，仅传输每个峰值的幅度，在此模式下，同时扫描所有三个质量范围所需的时间为1秒。还可能存在其他操作模式。在模拟短模式下，三个质量范围在2秒内扫描，与1秒的“峰值”模式扫描交替进行。在模拟长模式下，需要8秒的扫描时间，同样与1秒的“峰值”模式扫描交替进行。在锁定模式下，可以选择连续测量质量比为1-4-16的任意一组质量数，以获得高空间分辨率。更多实验细节可参考J. H. Hoffman等人发表在《Radio Sci.》第8卷第4期第315页的文章（1973年）。NSSDC拥有该研究所有有用的数据。