Weak lensing studies from space with GEMS

The Galaxy Evolution from Morphology and SEDs (GEMS) survey is the largest contiguous field ever imaged in colour by HST with the Advanced Camera for Surveys (ACS), spanning some 900 square arcmins in the Chandra deep field south (CDFS). We discuss the power of the ACS for weak lensing studies and present preliminary results from our cosmic shear analysis of GEMS. Selecting a subset of GEMS galaxies which are resolved in deep ground-based R-band imaging of the CDFS from the COMBO-17 survey, we compare the cosmic shear signal determined from the ground and from space.