ICON's Extreme Ultraviolet (EUV) instrument is an “imaging spectrometer”. Its 2 dimensional detector records spectral information over the range 58.4 to 83.4 nm in the one direction, and records 12 degree wide x 1/4 degree high slices of the sky over a 16 degree field of view in the other direction.
In preparation for alignment of the toroidal grating used in the EUV instrument, an optical system has been setup to simulate the cylindrical wavefront. This simulates the instrument’s view for each slice of sky while in orbit. The optical set up consists of a convex sphere and a concave toroid that produces a line image on the EUV entrance slit to simulate what EUV will observe in space. This optics pair will be used to first align the EUV instrument using visible light, then the final alignment will take place in a vacuum chamber using EUV radiation, since EUV light is not transmitted in air.