Roll Differential Imaging for PSF Suppression and High-Contrast Ratios
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Many of the most fascinating inquiries within modern astrophysics currently require the creation of new, more advanced data collection techniques that are capable of resolving issues produced by extreme contrast ratios (ECRs). ECRs characterize situations where there is a tremendous discrepancy in the relative brightness of two astrophysical objects. In order to observe the fainter of the objects, the effect of a point spread function (PSF) must be suppressed. PSF suppression can be achieved through “classical” methods, but these often lead to significant costs and complications. As a result, there exist two much simpler techniques for high-contrast ratio imaging: space-based roll subtraction and ground-based angular differential imaging (ADI). Roll subtraction generates a difference image from collected data at two different spacecraft roll angles (Figure 1). The major disadvantage of roll subtraction is that substantial residual signal remains in the final image. ADI utilizes an ALT-AZ telescope configuration with a disabled rotator plate, allowing the rotation of the sky to produce multiple field orientations. The raw images are median combined to create a model PSF, which can then be removed from the individual images before derotating and combining again. We present a novel data analysis technique called roll differential imaging which makes use of both ground-based and space-based methods. Roll differential imaging (RDI) combines the pre-established roll subtraction and ADI techniques to provide a new, simple, and effective approach to dealing with ECRs.