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The Space Telescope Imaging Spectrograph (STIS) is being developed for in-orbit installation into the Hubble Space Telescope (HST) in 1997. STIS will cover the wavelength range 115 to 1000nm with resolving powers from 26 to 100,000. Two dimensional detectors (1024 x 1024 pixels) will allow long-slit imaging spectroscopy, echelle spectroscopy with broad simultaneous wavelength coverage, and imaging. For observing QSO absorption lines, two instrumental features of STIS are of interest compared to the current HST spectrographs. At a resolving power of 24000 the spectral range 115-170nm can be covered in one exposure, and 165-310nm in 2 exposures, more than an order of magnitude increase in coverage. This may be used for detailed diagnostics of absorption line systems in relatively bright QSOs. At a resolving power of 400-1100, fainter QSOs may be observed than previously because of the lower detector background of the MAMA detectors compared to the digicons, due to smaller pixels and Cerenkov anticoincidence. This will be useful, for example, in studies of the Gunn-Peterson effect in helium.
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