The SOLIS Integrated Sunlight Spectrometer (ISS) is designed
to obtain both high (R = 300,000) and moderate (R = 30,000) spectral resolution
observations of the Sun as a star. ISS provides observations of disk-integrated
sunlight through the use of a fiber optic feed. A small optical system utilizing
a lens of 8-mm diameter will focus a 400 micron diameter image of the Sun on the
input face of the fiber. The output beam from the fiber will consist of sunlight
scrambled in both angle and position so that any output angle from any position
on the exit face will be well-integrated. A prism pre-disperser will isolate
the desired wavelength band. The McPherson 2-m Czerny-Turner spectrograph in
the ISS employs a 316 g/mm grating blazed at 63.5 degrees. The focal plane
detector is a movable, back-illuminated 1024 X 256 CCD. Among the many
wavelengths measured are the Ca II H and K lines at 396.8 and 393.4 nm,
He I 1083 nm, H-alpha 656.3 nm, and the Ca II triplet at 854.2 nm.