CORRECTING FOR ROLLING SHUTTER DISTORTION IN DART OPTICAL NAVIGATION IMAGERY

A key process in optical navigation (opnav) is the use of observed star centers, combined with a known camera model, to derive the pointing of a given picture1. This process typically produces attitude accuracies on the order of a tenth or hundredths of a pixel. However, as CMOS detectors become increasingly common in opnav cameras, so to does the use of a rolling shutter, as is the case for the Double Asteroid Redirection Test (DART) Didymos Reconnaissance and Asteroid Camera for Opnav (DRACO). A rolling shutter means that as the spacecraft deadbands, each readline is exposed at a slightly different attitude, thus distorting the resulting star pattern, and potentially inducing error to the process of estimating picture attitude. This paper details these effects on DRACO imagery, and the techniques developed to counteract them.