The Pierre Auger Observatory is a cosmic-rayobservatory
in western Argentina, in operation since about 2006,
completed to its intended extent in 2008.
It consists of Cherenkov detectors,
widely-distributed for a 3,000 km² detection
area, at a considerable elevation,
at a remote location near the Andes.
It aims for the highest energy cosmic rays, e.g., 1018
to 1020eV and beyond
(UHE cosmic rays/UHECRs and EE cosmic rays/EECRs),
and its large collecting area is to accommodate their rarity.
The name AugerPrime is used for a c2020 upgrade to the
observatory.