Cooled grating array spectrometer for 0.6-5 microns

Abstract

A grating spectrometer, designed to illuminate an array of 122 InSb photodiodes with minimum aberrations and maximum speed, has been constructed. The instrument will be used on the 5 meter Hale telescope at Palomar Observatory, and is easily adaptable to telescopes of various focal ratios. A resolving power of 100-1000 can be obtained at wavelengths between 0.6 microns and 5 microns with remotely interchangeable gratings. The spectrometer is sufficiently compact to fit on the 8-inch work surface of a commercially available dewar, and uses simple on-axis spherical and paraboloidal optical elements. The camera mirror produces an f/2.5 beam which, with the 0.2 mm detectors, allows a 3-in. focal-plane aperture on the 5 meter telescope. All rays fall within a 100 microns blur circle at all points along the array. Distortions have been corrected with a tilted field flattening lens in front of the detector.