Spitzer's Infrared Spectrograph
The Infrared Spectrograph(IRS) is one of the three instruments onboard Spitzer and provides both high- and low-resolution
spectroscopy at mid-infrared wavelengths. Spectrometers are instruments which spread light out into its constituent
wavelengths creating a spectra. Within this spectra, astronomers can study emission and absorption lines: which are the
fingerprints of atoms and molecules.
The IRS has four separate modules: a low-resolution, short-wavelength mode covering the 5.3-14 micron interval; a
high-resolution, short-wavelength mode covering 10-19.5 microns; a low-resolution, long-wavelength mode for observations
at 14-40 microns; and a high-resolution, long-wavelength mode for 19-37 microns. Each module has its own entrance slit to
let infrared light in. The detectors are 128 x 128 arrays. The shorter-wavelength silicon detectors are treated with arsenic; the
longer-wavelength silicon detectors are treated with antimony.
The IRS instrument consists of two physically separated parts, the cold assemblies which are located within the Spitzer
multiple instrument chamber and the warm electronics, which are located in the Spitzer spacecraft bus. The IRS has no moving parts!