Linearity and high signal-to-noise performance of the STIS CCD

On-orbit data characteristics of the Space Telescope Imaging Spectrograph ( STIS) CCD aboard the Hubble Space Telescope have been explored with early c alibrations in a number of limiting conditions. At a gain of 4 e(-) DN-1, S TIS CCD data show excellent linearity at high count levels, even for extrem e oversaturation of individual central pixels. At low count levels we inter pret a position- and intensity-dependent nonlinearity in terms of charge tr ansfer (in)efficiency in the parallel clocking direction and provide a simp le model that accounts for this. A short time series of spectra was acquire d at short-exposure times and high signal-to-noise ratio (S/N) on the binar y system a Cen A and B enabling the shutter repeatability to be quantified at 0.0002 s, A direct demonstration of near-Poisson-limited time series wit h S/N > 3000 is shown.