Interpretation of results of deconvolved images from the Deep Impact spacecraft High Resolution Instrument

A flaw in the pre-launch calibration system resulted in an inability to accurately focus the Deep Impact’s High Resolution Instrument (HRI). This defocus resulted in a significant loss of resolution. The nature of the blurring function allows us to use image restoration techniques to retrieve much of the lost resolution. These techniques can produce artifacts in the image such as noise amplification and unwanted oscillations (at the level of 10% of the peak value in the restored point source) in the restored signal. Much useful information, including photometry of point sources, can be extracted from the restored HRI images of Comet Hartley 2, and other images from the Deep Impact spacecraft. In this paper, we present techniques for evaluating the restored images both qualitatively and quantitatively. Monte Carlo techniques are suggested to assess the accuracy of point source photometry.