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 calibrations in a number of limiting conditions. At a gain of 4 e^- DN^-1, STIS CCD data show excellent linearity at high count levels, even for extreme oversaturation of individual central pixels. At low count levels we interpret a position- and intensity-dependent nonlinearity in terms of charge transfer (in)efficiency in the parallel clocking direction and provide a simple model that accounts for this. A short time series of spectra was acquired at short-exposure times and high signal-to-noise ratio (S/N) on the binary 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 with S/N > 3000 is shown.