Dithering Strategies for Efficient Self‐Calibration of Imaging Arrays

With high sensitivity imaging arrays, accurate calibration is essential toachieve the limits of detection of space observatories. One can simultaneouslyextract information about the scene being observed and the calibrationproperties of the detector and imaging system from redundant dithered images ofa scene. There are large differences in the effectiveness of ditheringstrategies for allowing the separation of detector properties from skybrightness measurements. In this paper, we quantify these differences bydeveloping a figure of merit (FOM) for dithering procedures based on theirusefulness for allowing calibration on all spatial scales. The figure of meritmeasures how well the gain characteristics of the detector are encoded in themeasurements, and is independent of the techniques used to analyze the data.Patterns similar to the antenna arrangements of radio interferometers with goodu-v plane coverage, are found to have good figures of merit. We presentpatterns for both deep surveys of limited sky areas and for shallow surveys. Bychoosing a strategy that encodes the calibration in the observations in aneasily extractable way, we enhance our ability to calibrate our detectorsystems and to reach the ultimate limits of sensitivity which are required toachieve the promise of many missions.Comment: Scheduled for ApJ, June 10, 2000 (22 pages, 9 figures