Genesis Plasma Spectrometers

There are two solar wind spectrometers on-board the Genesis spacecraft: the Genesis Ion Monitor (GIM) and the Genesis Electron Monitor (GEM). The primary purpose of these spectrometers is to enable the collection of appropriate samples of the solar wind by the Genesis sample collectors. This involves determining the type of solar wind that is flowing past the spacecraft, adjusting high-voltages in the Concentrator for the current conditions and deploying the appropriate Collector Array for the type of solar wind present, all in realtime. The secondary function of the Monitors is to obtain high-quality solar wind data that can be used for various scientific studies. Interested parties are referred to the detailed instrument description paper by Barraclough et al. (2003), listed on the publications page.
Genesis Ion Monitor (GIM)
GIM consists of a 120-degree spherical-section electrostatic analyzer (ESA) followed by an array of eight channel electron multipliers (CEMs) for energy and angle analysis of incoming ions. The ESA is negatively biased by a high-voltage power supply that steps across a number of voltage levels to build up an energy spectrum of the plasma population. The GIM is basically an E/q analyzer but does have a mass analysis capability in this instance due to the similar flow velocities of all ions in the solar wind beam. The energy range of the instrument is ~100 eV to 14 keV, with a resolution of 5.2%, but only a small fraction of this range is used at any one time. Onboard software tracks the solar wind flow speed and autonomously adjusts the energy range that is scanned to keep it centered on the beam.
GIM has a field-of-view (FOV) that is ~3.0 degrees in azimuth by ~26 degrees in polar angle and one of the narrow edges of the FOV is aligned such that it slightly overlaps the spacecraft rotational axis. Given this configuration, during one spin of the spacecraft GIM sweeps out a circle on the sky that is ~24 degrees in radius with the center of the circle being coincident with the average solar wind flow direction at 1 AU. During each spin, GIM steps forty times across ten individual energy steps and this process is repeated for four spins of the spacecraft with the energy steps being varied for each spin. These four spins comprise a complete data cycle and require approximately 2.5 minutes to complete. Thus GIM acquires a complete measurement of the ion distribution function every 2.5 minutes. The data product consists of ion counts for eight polar angle and forty azimuthal angles and forty energy levels.
Genesis Electron Monitor (GEM)
The GEM sensor head is almost an identical copy of the electron spectrometers that are currently flying on ACE (SWEPAM-E) and on Ulysses (BAM-E) but the electronics are of a new design. Basically, GEM consists of a 120 degree ESA that is backed by an array of seven CEMs for energy-angle analysis of incident plasma electrons. The energy range of the instrument is 1 to 1400 eV, the energy resolution is ~14%, and the FOV is ~12 degrees in azimuth (this varies somewhat with polar angle) by ~150 degrees in polar angle. The center of the FOV is centered along a normal to the spacecraft spin axis and consequently the FOV sweeps out approximately 94% of the sky during each spin. Data acquisition of the GEM is synchronized with that of the GIM and also takes four spins of the spacecraft to execute. A complete data matrix for the GEM consists of electron counts for seven polar angles and twenty four azimuthal angles and twenty energy levels.
Both the GEM and GIM were in continuous operation since shortly after launch in August 2001 until August 04, 2004, a month before sample re-entry.

搭载于‘创世’航天器上的太阳风光谱仪共有两种：创世离子监测仪（GIM）和创世电子监测仪（GEM）。这些光谱仪的主要职能在于协助创世样本收集器收集适合的太阳风样本。此过程包括确定流经航天器的太阳风类型、根据当前条件调整集光器的高电压，并实时部署适用于现有太阳风类型的适当收集阵列。其次，监测仪的次要功能是获取高质量的太阳风数据，这些数据可用于多种科学研究。有兴趣的各方可参考Barraclough等人（2003年）发表在出版物页面上的详细仪器描述论文。

创世离子监测仪（GIM）：GIM由一个120度的球形截面的静电分析仪（ESA）和一个由八个通道电子倍增器（CEMs）组成的阵列构成，用于对入射离子的能量和角度进行分析。ESA通过一个高压电源进行负偏置，该电源跨越多个电压等级以构建等离子体人群的能量谱。GIM本质上是一个E/q分析仪，但在此实例中由于太阳风束中所有离子的流速相似，因此具备质量分析能力。仪器的能量范围为约100 eV至14 keV，分辨率为5.2%，但任何一次仅使用该范围的一小部分。机载软件跟踪太阳风流速，并自主调整扫描的能量范围，以保持其中心对准光束。

GIM的视场（FOV）约为3.0度方位角和26度极角，其中视场的一个狭窄边缘与航天器旋转轴略重叠。据此配置，在航天器的一次自转过程中，GIM在天空中扫出一个半径约为24度的圆圈，圆心与1 AU处的平均太阳风流向一致。在每次自转中，GIM在十个独立能量步骤上移动四十次，这一过程在航天器自转四次后重复，每次自转的能量步骤均有所不同。这四次自转构成了完整的数据周期，需要大约2.5分钟来完成。因此，GIM每2.5分钟获得一次完整的离子分布函数测量。数据产品包括八个极角和四十个方位角以及四十个能量水平的离子计数。

创世电子监测仪（GEM）：GEM传感器头几乎与目前搭载在ACE（SWEPAM-E）和Ulysses（BAM-E）上的电子光谱仪完全相同，但电子学设计为全新。基本上，GEM由一个120度的ESA和一个由七个CEMs组成的阵列构成，用于对入射等离子体电子进行能量-角度分析。仪器的能量范围为1至1400 eV，能量分辨率为约14%，FOV约为12度方位角（随极角变化）和150度极角。FOV的中心与航天器自转轴的法线对齐，因此，在每次自转中，FOV扫过大约94%的天空。GEM的数据采集与GIM同步，并需要航天器自转四次来执行。GEM的完整数据矩阵包括七个极角、二十四方位角和二十个能量水平的电子计数。

GEM和GIM自2001年8月发射后的不久起一直处于连续运行状态，直至2004年8月4日，即样本再入前的一个月。