  With high sensitivity imaging arrays, accurate calibration is essential to
achieve the limits of detection of space observatories. One can simultaneously
extract information about the scene being observed and the calibration
properties of the detector and imaging system from redundant dithered images of
a scene. There are large differences in the effectiveness of dithering
strategies for allowing the separation of detector properties from sky
brightness measurements. In this paper, we quantify these differences by
developing a figure of merit (FOM) for dithering procedures based on their
usefulness for allowing calibration on all spatial scales. The figure of merit
measures how well the gain characteristics of the detector are encoded in the
measurements, and is independent of the techniques used to analyze the data.
Patterns similar to the antenna arrangements of radio interferometers with good
u-v plane coverage, are found to have good figures of merit. We present
patterns for both deep surveys of limited sky areas and for shallow surveys. By
choosing a strategy that encodes the calibration in the observations in an
easily extractable way, we enhance our ability to calibrate our detector
systems and to reach the ultimate limits of sensitivity which are required to
achieve the promise of many missions.
