The grazing incidence spectrometer (GIS) has a
grazing incidence spherical grating that disperses the incident light
to four microchannel plate (MCP) detectors placed along the Rowland Circle
(GIS 1: 151 - 221 Å,
GIS 2: 256 - 341 Å, GIS 3: 393 - 492 Å and GIS 4: 659 - 785 Å;).
The spectral resolution of the GIS detectors is about 0.5 Å.
Many second order lines have been observed in GIS 3 and GIS 4.
The GIS is
astigmatic, focusing the image of the slit along the direction of
dispersion but not perpendicular to it.
Images of the Sun are obtained using a pinhole slit and combining
movements of the slit and of the scan mirror.
Normally, the movements are such that an area of the Sun is rastered
in a zig-zag pattern, starting from south to north and from west to east
(in normal CDS alignment).
