Performance and calibration of the HST Wide Field Camera 3

The WFC3 is the primary science instrument on HST. It accounts for over half of all observations since its installation during SM4 in May 2009. We discuss the evolution of our understanding of the performance of WFC3 and our calibration strategies. A key aspect of WFC3 is its high degree of stability which permits steadily improving calibrations. We discuss four main topics: the calibration and trending of photometric and astrometric observations, the techniques we are using to achieve markedly improved flat field calibrations (and their associated challenges), the evolution of the WFC3 CCD and HgCdTe detectors in the space environment, and the recent implementation of a spatial scanning observing technique which enables very high signal to noise ratio observations of bright sources including exo-planets and also high precision astrometry.