High Energy Neutral Atom (HENA) Imager for the IMAGE Mission

D. G. Mitchell, S. E. Jaskulek, C. E. Schlemm, E. P. Keath, R. E.
Thompson, B. E. Tossman, J. D. Boldt, J. R. Hayes, G. B. Andrews, and N.
Paschalidis
The Johns Hopkins University Applied Physics Laboratory

D. C. Hamilton, R. A. Lundgren, E. O. Tums, P. Wilson IV, 
The University of Maryland

H. D. Voss, D. Prentice 
Taylor University

K. C. Hsieh, C. C. Curtis 
The University of Arizona

F. R. Powell
Luxel Corporation


            The IMAGE mission will be the first of its kind, designed to
comprehensively image a variety of emissions from the Earth's magnetosphere, 
with sufficient time resolution to follow the dynamics associated with the 
development of magnetospheric storms.  Energetic neutral atoms (ENA) emitted 
from the ring current during storms are one of the key emissions that will 
be imaged.  This paper describes the characteristics of the High Energy 
Neutral Atom imager, HENA. 
	Using pixelated solid state detectors, imaging microchannel plates,
electron optics, and time of flight electronics, HENA is designed to return 
images of the ENA emitting regions of the inner magnetosphere with 2 minute 
time resolution, at angular resolution of 8 degrees or better above the 
energy of ~ 50 keV/nucleon.  HENA will also image separately the emissions 
in hydrogen, helium, and oxygen above 30 keV/nucleon.  HENA will reject 
energetic ions below 200 keV/charge, allowing ENA images to be returned in 
the presence of ambient energetic ions. 
	HENA images will reveal the distribution and the evolution of energetic
ion distributions as they are injected into the ring current during
geomagnetic storms, as the drift about the Earth on both open and closed 
drift paths, and as they decay through charge exchange to pre-storm levels.  
Substorm ion injections will also be imaged, as will the regions of low 
altitude, high latitude ion precipitation into the upper atmosphere.

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Space Science Reviews, IMAGE Special Issue, Vol. 91, pp. 67-112, February, 2000