Are all collected Landsat scenes held in the USGS Landsat archive?

No. While the USGS Landsat archive contains a large number of collected Landsat scenes, some international scenes may not be held in the USGS Landsat archive.  Each ground station in the International Cooperator (IC) network is currently the primary source for distributing the captured data in their area, so data not found in the USGS archive may be available from the ground station that collected the data. Contact information and a coverage map of the IC network can be found at this USGS International Ground Station (IGS) Network website.

There have been data exchanges between the USGS and some ICs, and the Landsat Global Archive Consolidation (LGAC) effort is underway. These scenes are copied into the USGS Landsat archive and made available for searching and downloading from GloVis and EarthExplorer.