Construction has started on the Large High Altitude Air Shower Observatory (LHAASO) in Haizi Mountain in Sichuan Province in southwest China. It is expected to be completed in 2020.

LHAASO aims to detect cosmic rays over a wide range of energies from 10111018 eV using 10 Cherenkov water detectors, covering a total area of 80 000 m2, together with 12 wide-field Cherenkov telescopes. These two types of instrument, which are above ground, will spot the Cherenkov radiation emitted when a charged particle travels through a medium faster than light can travel through that medium. Below ground, LHAASO will also consist of a 1.3 km2 array of 6000 scintillation detectors that will study electrons and photons in the air showers, while an overlapping 1.3 km2 array of 1200 underground Cherenkov water tanks will detect muons.

LHAASO is not the only facility in the world trying to study the origin of cosmic rays. The IceCube facility at the South Pole observes high-energy neutrinos, while the Pierre Auger Observatory in Argentina explores cosmic rays with energies above 1018 eV. "LHAASO will play a complementary role with existing detectors to offer a more comprehensive picture of the cosmic-ray sky," says Yifang Wang, head of the Institute of High Energy Physics (IHEP) of the Chinese Academy of Sciences.
LHAASO is an international collaboration that includes scientists from China, France, Italy, Russia, Switzerland and Thailand. First mooted in 2008, the facility won approval from the National Development and Reform Commission of China in December 2015. Haizi Mountain was selected as the site due to its high elevation and good accessibility being only 10 km away from Yading Airport the world's highest and about 50 km from Daocheng County, which will be the base for the LHAASO team.