Abstract
Extreme Ultraviolet Imagers (EUVIs) are the parts of the IMAP (Ionosphere, Mesosphere, upper Atmosphere, and Plasmasphere mapping) mission that aims to elucidate the physical mechanisms in the boundary region between the Earth system and the outer space. In order to reveal the energy transport process in the upper atmosphere, EUVIs direct towards the Earth’s limb and observe helium ions and oxygen ions in the ionosphere and plasmasphere. The EUVIs consist of two normal-incidence telescopes. One telescope detects resonantly-scattered emission from helium ion at the wavelength of 30.4 nm and the other detects oxygen ion emission at 83.4 nm. The primary mirror employs Al/Y2O3 multilayer coating technique. The detector consists of a 5-stage microchannel plate assembly and a resistive anode encoder. A metallic thin filter is installed in front of the detector to exclude the bright geocoronal emission at 121.6 nm. Each telescope has a field of view of 13.2 degrees, a spatial resolution of 0.1 degree and a time resolution of 1minute. EUVIs were successfully launched in July 2012 and are now providing images of the plasma distribution in the ionosphere and plasmasphere.
