| Institution: | (1) Southwest Research Institute, 6220 Culebra Road, San Antonio, TX, 78238-5166, U.S.A.;(2) Institute of Space and Astronautical Sciences, 311 Yoshinodai Sagamihara, Kanagawa, 229-8510, Japan;(3) Los Alamos National Laboratory, CSSE/NIS-1, Los Alamos, NM, 87545, U.S.A.;(4) Department of Physics, West Virginia University, Box 6315, Morgantown, WV, 26506, U.S.A.;(5) Space Sciences Laboratory, University of California at Berkeley, Centennial Drive at Grizzly Peak Blvd, Berkeley, CA, 94720, U.S.A.;(6) Universities Space Research Association, NASA GSFC, Greenbelt, MD, 20771, U.S.A.;(7) Rutherford Appleton Laboratory, Oxfordshire, OX11 0QX, England;(8) Department of Aerospace Engineering, University of Southern California, Los Angeles, CA, 90089, U.S.A.;(9) Philips Research Laboratories, Prof. Holstlaan 4, 5656 AA Eindoven, The Netherlands |
| Abstract: | The Medium Energy Neutral Atom (MENA) imager was developed in response to the Imaging from the Magnetopause to the Aurora for Global Exploration (IMAGE) requirement to produce images of energetic neutral atoms (ENAs) in the energy range from 1 to 30 keV. These images will be used to infer characteristics of magnetospheric ion distributions. The MENA imager is a slit camera that images incident ENAs in the polar angle (based on a conventional spherical coordinate system defined by the spacecraft spin axis) and utilizes the spacecraft spin to image in azimuth. The speed of incident ENAs is determined by measuring the time-of-flight (TOF) from the entrance aperture to the detector. A carbon foil in the entrance aperture yields secondary electrons, which are imaged using a position-sensitive Start detector segment. This provides both the one-dimensional (1D) position at which the ENA passed through the aperture and a Start time for the TOF system. Impact of the incident ENA on the 1D position-sensitive Stop detector segment provides both a Stop-timing signal and the location that the ENA impacts the detector. The ENA incident polar angle is derived from the measured Stop and Start positions. Species identification (H vs. O) is based on variation in secondary electron yield with mass for a fixed ENA speed. The MENA imager is designed to produce images with 8°×4° angular resolution over a field of view 140°×360°, over an energy range from 1 keV to 30 keV. Thus, the MENA imager is well suited to conduct measurements relevant to the Earth's ring current, plasma sheet, and (at times) magnetosheath and cusp. |
