content long 19-May-2013 05:58:56

Hubble instruments

COS - Cosmic Origins Spectrograph

Cosmic Origins Spectrograph (COS). Credit: Ball Aerospace & Technologies

The Cosmic Origins Spectrograph (COS) is a fourth-generation instrument to be installed on the Hubble Space Telescope (HST) during Servicing Mission 4. It will be installed in the instrument bay currently occupied by COSTAR, the set of corrector mirrors on deployable arms that provided corrected light beams to the first generation of Hubble instruments. COSTAR is no longer used or required.

COS is designed to perform high sensitivity, medium- and low-resolution spectroscopy of astronomical objects in the ultraviolet. COS will significantly enhance the spectroscopic capabilities of HST at ultraviolet wavelengths, and will provide observers with unparalleled opportunities for observing faint sources of ultraviolet light. COS complements the possibilities of the STIS instrument.

The primary science objectives of the instrument are the study of the origins of large scale structure in the universe, the formation and evolution of galaxies, and the origin of stellar and planetary systems and the cold interstellar medium. The instrument has been designed with maximum effective area as the primary constraint, and will provide more than an order of magnitude gain in sensitivity over previous HST instruments in this wavelength region.

COS has two 2.5 arcsec diameter circular apertures. The primary science aperture (PSA) is a full-transmission aperture expected to be used for most normal science observations. The bright object aperture (BOA) is used for observations requiring flux attenuation. The BOA contains a neutral density (ND2) filter that attenuates the flux by a factor of 200 (about 6 magnitudes).

After passing through either of the two apertures, light entering the COS passes an optical element that directs the light onto one of two detectors with different wavelength coverage: far-ultraviolet (FUV) or near-ultraviolet (NUV). The FUV detector is a windowless, crossed delay-line microchannel plate (MCP) stack optimized for the 1150 to 1775 Å bandpass. The NUV detector is a multi-anode microchannel array (MAMA) optimized for spectroscopic observations in the 1700-3200 Å bandpass. The COS MAMA is similar to the NUV MAMA used on the STIS instrument.

COS Facts
Instrument type Spectrograph
Wavelength Range
FUV: 1150 < λ < 2050 Å
NUV: 1700 < λ < 3200 Å
Resolution
(for both FUV and NUV)
low: R= ~ 2000 - 3000
medium: R= ~ 16 000 - 24 000

Last Update: 04 June 2009

For further information please contact: SciTech.editorial@esa.int

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