to a fixed location. In the extraction lens, the ions are accelerated by 20 kV prior to entering the electrostatic analyzer. Finally, the ions pass into a time-of-flight/position sensing section where ion mass, energy, and angle are determined. 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 DPU. The three sensor heads are mounted side by side on top of the DPU. The middle sensor looks straight ahead, with a 107° 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°. This 20° offset compensates for a 20° blind spot in the center of each detector. The resulting field of view in the plane of the spin axis is 147°. 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 supply, 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. Radio Plasma Imager (RPI) The Radio Plasma Imager (RPI) used pulses of radio waves to "sound" nearly the entire volume of the Earth's magnetic field. With its tip-to-tip antenna, it is one of the biggest sensors ever flown in space. Like a policeman's radar detector, the RPI's 10-watt transmitter sent out a burst of radio waves, which reflected off of clouds of charged particles