ISIS2 Ion Mass Spectrometer

The ISIS 2 (International Satellites for Ionospheric Studies) magnetic ion-mass spectrometer experiment measured the distribution of positive ion species as a function of time and position, with a particular focus on polar wind particles. The instrument had two ion detector systems, and mass scanning through the range from 1 to 64 atomic mass units (u) was accomplished in two sections, 1 to 8 u and 8 to 64 u. Two ion beams emerged from the magnetic sector of the instrument and were simultaneously detected by electron multipliers and log electrometer amplifiers. A circuit following each amplifier detected the peak amplitude of the ion current. That peak value, rather than the entire mass spectrum, was transmitted in order to reduce the required telemetry bandwidth. In that mode of operation, the complete mass range was scanned in 1 s. A backup mode was provided that produced an analog output with a sweep period of 8 s. This experiment operated nominally after launch with most of the data obtained in the peak mode and while the satellite operated in the cartwheel mode. For about 2 min per pass over Ottawa, Canada, the experiment operated in the analog mode. Inflight calibration was achieved by comparing ion concentration measurements at appropriate altitudes, i.e., where a single ion species predominated, with electron density data from the sounder on board. Other comparisons were made between the spectrometer output and measurements obtained from other related experiments on board.

ISIS 2（国际电离层卫星）磁离子质量光谱仪实验测量了正离子物种随时间和位置分布的情况，特别关注极光风粒子。该仪器配备有两个离子检测系统，通过两个部分，即1至8原子质量单位（u）和8至64原子质量单位（u），实现了质量扫描。两个离子束从仪器的磁场区域中射出，并由电子倍增器和对数电磁计放大器同时检测。每个放大器之后的电路检测到了离子电流的峰值幅度。该峰值值而非整个质量光谱被传输，以减少所需的遥测带宽。在这种操作模式下，整个质量范围在1秒内完成扫描。提供了一种备用模式，该模式产生一个8秒扫描周期的模拟输出。该实验在发射后正常运行，大部分数据在峰值模式下获得，同时卫星处于旋转模式。在加拿大渥太华上空每经过约2分钟，实验在模拟模式下运行。通过比较适当高度处的离子浓度测量值，即单一离子物种占主导地位的高度，与机载测距仪的电子密度数据，实现了在飞行中的校准。还进行了光谱仪输出与其他相关实验的测量值之间的比较。