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 α 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.