MMS 4 Active Spacecraft Potential Control (ASPOC), Sensors 1 and 2, Level 2 (L2), Survey Mode, 1 s Data

MMS 4 Active Spacecraft Potential Control (ASPOC) - Sensors 1 and 2 Ion Beam Current Rates, Beam Energies, and Instrument Status variables. In tenuous plasma regions, the floating potential of a sunlit spacecraft is positively charged, reaching up to tens of Volts. The corresponding electric field disturbs the ambient plasma measurements obtained from electron and ion sensors and the large fluxes of attracted photo-electrons can significantly reduce the lifetime of the micro-channel plate. The electric field measurements can be also contaminated by the high spacecraft potential values. The Active Spacecraft Potential Control neutralizes the spacecraft potential by releasing positively charged Indium ions. The ASPOCs neutralize the electrical potential of the spacecraft, limiting or eliminating spurious electric fields that can contaminate measurements. This allows observations of the more scientifically important low-energy ions and electrons.

MMS 4 有源航天器电位控制（Active Spacecraft Potential Control，ASPOC）—— 传感器1与2的离子束电流速率、束能量及仪器状态变量数据集。在稀薄等离子体区域内，受日照的航天器浮动电位会带正电，最高可达数十伏特。由此产生的电场会干扰电子与离子传感器所获取的环境等离子体测量数据，而大量被吸引的光电子会显著缩短微通道板（micro-channel plate）的使用寿命。航天器电位过高还会对电场测量结果造成污染。有源航天器电位控制系统通过释放带正电的铟离子来中和航天器电位。ASPOC可中和航天器电位，限制或消除可能污染测量数据的杂散电场，从而能够开展科学价值更高的低能离子与电子观测。