Medium-Energy Neutral Atom Imager (MENA)

The Medium-Energy Neutral Atom (MENA) imager on IMAGE is one of three instruments designed to make observations of the Earth's magnetospheric environment using neutral atom imaging.
MENA is a slit-type imager designed to detect energetic neutral hydrogen and oxygen atoms with energies ranging from 1 to 30 keV. The instrument determines the time of flight and incidence angle of the incoming ENAs. From these raw data it calculates their trajectory and velocity and generates images of the magnetospheric regions from which they are emitted. The imager consists of three identical sensor heads mounted on a data processing unit (DPU).
The three sensor heads are mounted side by side on top of the DPU. The middle sensor looks straight ahead, with a 107-degree field of view in the plane of the spin axis. The look directions of the two side sensors are offset from that of the middle sensor by 20 degrees. This 20-degree o fset compensates for a 20-degree blind spot in the center of each detector. The resulting field of view in the plane of the spin axis is 147 degrees.
The MENA DPU consists of a single 16-bit Harris RTX2010 microcontroller operating at 4.91 MHz, look-up tables used to process the raw data, a low-voltage power suppy, a high-voltage controller, and, for each of the three sensors, the front end time-of- flight and pulse height electronics and high-voltage power supplies. The DPU communicates with the sensor heads and the Central Instrument Data Processor (CIDP). It monitors instrument health and safety and receives and processes the raw sensor data, producing one image every two minutes (i. e., each spacecraft spin period). It transmits this image, together with a selection of the raw sensor data, event rate data, and housekeeping data, to the CIDP for downlink to Earth.

IMAGE上的中能中性原子成像仪（MENA）是三个旨在通过中性原子成像手段观测地球磁层环境的仪器之一。MENA是一种狭缝式成像仪，旨在检测能量在1至30 keV范围内的活跃中性氢和氧原子。该仪器通过测定入射的ENAs（中性原子）的飞行时间和入射角度，从原始数据中计算出其轨迹和速度，并生成来自磁层区域的图像。成像仪由三个安装于数据处理单元（DPU）上的相同传感器头组成。三个传感器头并排安装在DPU顶部。中间的传感器朝正前方，其视场在自旋轴平面内为107度。两侧传感器的观测方向相对于中间传感器偏移20度。这一20度的偏移补偿了每个探测器中心的20度盲区。因此，在自旋轴平面内的视场达到147度。MENA的DPU由一个单16位Harris RTX2010微控制器组成，该微控制器以4.91 MHz的频率运行，用于处理原始数据的查找表，低电压电源，高压控制器，以及每个传感器的前端飞行时间脉冲高度电子设备和高压电源。DPU与传感器头和中央仪器数据处理器（CIDP）通信。它监控仪器的健康和安全状态，接收和处理原始传感器数据，每两分钟（即每次航天器自旋周期）生成一张图像。它将此图像以及选择性的原始传感器数据、事件速率数据和 housekeeping 数据传输到CIDP，以便下传至地球。