The Extrasolar Planet Observations and Characterization (EPOCh) investigation was a scientific component of the EPOXI mission. EPOXI re-used the Deep Impact flyby spacecraft to observe transiting extrasolar planets, and the Earth-as-an-extrasolar planet, while enroute to a 2010 encounter with comet Hartley-2. EPOCh used the High Resolution Imager (HRI) with its CCD camera to produce very precise photometry of giant extrasolar planets that transit nearby bright stars. Since the HRI was defocused, EPOCh could collect many stellar photons per exposure without saturating the detector, and thus produce very precise photometry of transits. The EPOCh team used these data to refine the physical properties of the giant planets, search for rings and moons that may orbit them, and search for smaller planets in these systems, down to the size of Earth.

EPOCh scientists connected to Goddard's Planetary Systems Laboratory include Drs. Drake Deming (Principal Investigator), Tim Livengood, and Tilak Hewagama.