On August 1, 2013, the High-Altitude Water Cherenkov (HAWC) Gamma Ray Observatory formally began operations.  HAWC is designed to study the origin of very high energy cosmic rays and observe the most energetic objects in the known universe.  This extraordinary observatory, which uses a unique detection technique that differs from the classical astronomical design of mirrors, lenses, and antennae, will position our country at the forefront of scientific and technical knowledge.

HAWC is located at an altitude of 14,000 ft (4,100 meters) above sea level on the slope of the Pico de Orizaba at the border between the states of Puebla and Veracruz.  The observatory, which is still under construction, uses an array of water Cherenkov detectors to observe high-energy cosmic rays and gamma rays.  Currently 111 out of 300 Cherenkov detectors are deployed and taking data.  Each Cherenkov detector consists of 200,000 liters of extra-pure water stored inside an enormous tank (5 meters high and 7.3 meters in diameter) with four highly sensitive light sensors fixed to the bottom of the tank.

The construction and operation of HAWC has been made possible by the financial support of several Mexican institutions, and the National Science Foundation (NSF), the Department of Energy (DOE), the Los Alamos National Laboratory (LANL), and the University of Maryland in the United States.

The HAWC array, operating with 111 Cherenkov detectors since August 1, has begun sensitive detections of high-energy particles and radiation between 100 GeV and 100 TeV.