Exploring Strange New Worlds: From Giant Planets to Super Earths

Spatial Scanning with HST for Exoplanet Transit Spectroscopy and other High Dynamic Range Observations
We are reviving an old technique of spatially scanning the telescope to improve observations, in this case with the Hubble Space Telescope's Wide Field Camera 3 (HST WFC3). Spatial scanning will turn stars into well-defined streaks on the detector, or, for example, spread a stellar spectrum perpendicular to its dispersion. There are at least two motivations for implementing such a capability: 1) reducing the fraction of overhead in observations of very bright stars such as those suitable for spectral characterization of transiting planets, and 2) enabling observations of very bright primary calibrators that otherwise would saturate the IR detector. We report results (McCullough & MacKenty 2011) from two engineering tests in which a star was imaged with WFC3 IR under various parameterizations of HST's scanning speed and orientation, and with or without a grism in place.
P. R. McCullough & J. MacKenty 09 May 2011 (pdf)