Title: One trillion time-tagged photons Abstract: The Galaxy Evolution Explorer is an ultraviolet space telescope that has been mapping the UV sky for over five years. Unbeknownst to most astronomical users, GALEX images are produced using a raw data set of nearly one trillion time-tagged photon positions. I will describe the computational and algorithmic challenges posed by this vast data set, several solutions, and some unique but still largely unexplored astronomical applications. These methods are becoming increasingly relevant with the advent of low light level CCDs and other highly efficient photon-counting detectors.