The chart below displays the number of scenes visible to all users on EarthExplorer as of December 31, 2014.
Active Landsat 8 and Landsat 7 acquisitions constantly increase the number of available scenes in the USGS archives. In addition, the Landsat Global Archive Consolidation (LGAC) effort has allowed more historical Landsat 1-5 MSS and TM scenes to become visible and available to all users.
The files on the USGS Landsat Global Archive webpage (http://landsat.usgs.gov/USGSLandsatGlobalArchive.php) provide a view of the data added to the USGS archive per satellite, per year.
This scene represents one of the path/rows from which most scenes were downloaded in December 2014.
Landsat 8 Path 15 Row 33 Acquired November 18, 2014
This image shows the Chesapeake Bay area in the eastern United States.
The Landsat archive became available to all users at no charge in December of 2008. As of January 21, 2015 over 22 million scenes have been downloaded.