Dithering strategies for efficient self-calibration of imaging arrays

With high-sensitivity imaging arrays, accurate calibration is essential to achieve the limits of detection of space observatories. One can simultaneou sly extract information about the scene being observed and the calibration properties of the detector and imaging system from redundant dithered image s of a scene. There are large differences in the effectiveness of dithering strategies for allowing the separation of detector properties from sky bri ghtness measurements. In this paper, we quantify these differences by devel oping a figure of merit (FOM) for dithering procedures based on their usefu lness for allowing calibration on all spatial scales. The figure of merit m easures how well the gain characteristics of the detector are encoded in th e measurements, and is independent of the techniques used to analyze the da ta. Patterns similar to the antenna arrangements of radio interferometers w ith good u-nu plane coverage are found to have good figures of merit. We pr esent patterns for both deep surveys of limited sky areas and for shallow s urveys. By choosing a strategy that encodes the calibration in the observat ions in an easily extractable way, we enhance our ability to calibrate our detector systems and to reach the ultimate limits of sensitivity that are r equired to achieve the promise of many missions.