Source: USGS Landsat Project
• Landsat satellites have acquired data from across the globe for more than four decades. The National Satellite Land Remote Sensing Data Archive at the U.S. Geological Survey (USGS) Earth Resources Observation and Science (EROS) Center holds the single most geographically and temporally rich collection of Landsat data in the world, currently holding more than three million Landsat scenes.Throughout the years, Landsat data have also been acquired at numerous International Ground Stations (IGS). Much of the data held internationally are unique, relative to each station’s area of coverage, and not duplicated in the USGS archive.
The Landsat Global Archive Consolidation (LGAC) effort started in 2010, with a goal to consolidate the Landsat archives of all stations worldwide and make all Landsat scenes available to users.
Bringing Landsat data from many collection stations worldwide to one archive includes several challenges:

• Various data formats and processing methods
  Unknown data formats and processing methods (stations no longer active)
• Media storage age and conditions
• Various or obsolete technologies used to ingest data
• While every technology asset available will be explored, some data may be irrecoverable.

This effort to systematically acquire, reconcile, and ingest all recoverable foreign data is estimated to last up to six years. As data are successfully ingested, the Landsat scenes will become immediately available for download at no charge from EarthExplorer or GloVis.