In-flight Optical Performance of the Space Telescope Imaging Spectrograph

The Space Telescope Imaging Spectrograph (STIS) was installed aboard the Hubble Space Telescope (HST) in February, 1997, replacing the Goddard High Resolution Spectrograph and the Faint Object Spectrograph. STIS also incorporates an internal, two mirror relay system replacing COSTAR to correct the spherical aberration and astigmatism present at the STIS field position. STIS operates over the full HST wavelength range, from the ultraviolet to near infrared (115-1000nm). Spectroscopic modes permit low and medium resolution spectroscopy throughout the spectral range and over 25 arcsecond ultraviolet and 52 arcsecond visible fields. High resolution (30-100,000) echelle spectroscopy capability is also provided in the ultraviolet (115-310nm). Broad band imaging is possible over the complete spectral range and a small selection of bandpass filters are available. A wide selection of slits and apertures permit various resolution and spatial scales to be selected in all modes. Coronagraphic stops are also provided for observations in the visible (310-1000nm). On board calibration lamps provide wavelength calibration and flat fielding capability. The initial optical performance results obtained during orbital verification are presented here. These include absolute throughput and stability, camera mode image quality, spectroscopic resolution, and filter and slit transmission.