|Space Telescope Science Institute|
|COS Instrument Handbook Cycle 23|
1.1 The Cosmic Origins Spectrograph (COS) was installed on the Hubble Space Telescope (HST) in May 2009. Working at far-ultraviolet wavelengths, COS was designed to study the origins of large-scale structure in the Universe, the formation and evolution of galaxies, the origin of stellar and planetary systems, and the cold interstellar medium. COS significantly enhances the spectroscopic capabilities of HST at ultraviolet wavelengths, and provides observers with unparalleled opportunities for observing faint sources of ultraviolet light.COS offers two independent observing channels, a far-ultraviolet (FUV) detector, which is sensitive to wavelengths between 900 and 2150 Å, and a near-ultraviolet (NUV) detector for wavelengths from 1650 to 3200 Å. Both channels are equipped with medium-resolution (R ~ 20,000) and low-resolution (R ~ 3000) gratings. The NUV channel can also be used in imaging mode for both target acquisitions and scientific observations. The COS field of view is approximately 2.5 arcsec in diameter.