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5.10. Cosmic Origins Spectrograph (COS)

This new spectrograph will be installed in the bay currently occupied by COSTAR during the fourth servicing mission in 2002. COS is a large format slitless UV spectrometer with three gratings:

Table 25. COS characteristics

Wavelength Coverage Deltalambda / lambda

High Dispersion Channel 1 (HDC1) 1150Å - 1450Å 20000 - 24000
High Dispersion Channel 2 (HDC2) 1405Å - 1775Å 20000 - 24000
High Sensitivity Channel (HSC) 1230Å - 2000Å 2500 - 3000

The detector is a windowless microchannel-plate array, with an opaque CsI photocathode, and a double delay-lien readout. It is optimized for UV and far UV spectroscopy.

COS most frequent use will be in time-tag photon counting mode. For brighter target an image accumulation mode can be used too.