The USGS consistently delivers high quality Landsat products suitable for science research and analysis. On occasion, Landsat data may need to be reprocessed. Reprocessing events may be planned, or may be immediate, depending on the magnitude of the reason reprocessing is needed. Large-scale reprocessing efforts are rare and contain most or all of a specific dataset and are planned in advance.
You can discover scene and tile products that have been changed by reprocessing by accessing the Landsat Reprocessing Events search application. The results are displayed as shown in this image.
The background about the reprocessing of Landsat products, and details about this application, can be found on the Landsat Reprocessing Events webpage.