Take a set of HST data from one filter and exposure time (to start; later we will generalize) that have been CR-split (meaning: two images at each pointing). Shift-and-difference these split images to confidently identify a large number of cosmic rays. Pull out 5x5 image patches centered on cosmic-ray-corrupted pixels and 5x5 image patches not centered on cosmic-ray-corrupted pixels. Use these labeled data as training data for a supervised method that finds cosmic rays in single-image (not-CR-split) data. Improve value of HST data for all and obtain enormous financial gift from NASA in thanks (well, not really).
Notes: The most informative pixel patches will be those with faint cosmic ray pixels and those with bright stars that mimic cosmic rays. Some of this work has been started with (now graduated) NYU undergraduate Andrew Flockhart.