Beginning February 3, 2014, all Landsat 8 data held in the USGS archives will be reprocessed. All Landsat 8 scenes will be removed from the online cache at this time and the data will then be reprocessed starting with the most recent acquisitions and proceeding back to the beginning of the mission. Data will then become available for download. Scenes waiting to be reprocessed will also be available for on-demand product orders. Reprocessing is expected to take approximately 50 days.
Many corrections will be made to the data, affecting both the Operational Land Imager (OLI) and the Thermal Infrared Sensor (TIRS). These corrections include all calibration parameter file updates since launch; improved OLI reflectance conversion coefficients for the cirrus band; improved OLI radiance conversion coefficients for all bands; refined OLI detector linearization to decrease striping; a radiometric offset correction for both TIRS bands; and a slight improvement to the geolocation of the TIRS data.
Details about these changes are available on https://www.usgs.gov/landsat-missions/calibration_notices.php.
Source: USGS Landsat