Landsat Missions
Definitive Ephemeris is used for geometrically correcting Landsat data, and provides improved accuracy over predicted ephemeris. More details on Definitive Ephemeris can be found at http://landsat.usgs.gov/what_is_definitive_ephemeris.php.
Definitive Ephemeris files are available two days after acquisition, and can be accessed by choosing one of the options below: