Cosmic-ray observatory

[3] "In 1952, a simple and audacious experiment allowed the first observation of Cherenkov light produced by cosmic rays passing through the atmosphere, giving birth to a new field of astronomy".

[4] This work,[5] involving minimal instrument expense (a dustbin, a war-surplus parabolic mirror, and a 5 cm diameter photomultiplier tube), and based on a suggestion by Patrick Blackett, led ultimately to the current international multibillion-dollar investment in gamma ray astronomy.

Later, after Explorer 3, it was concluded that the original Geiger counter had been overwhelmed ("saturated") by strong radiation coming from a belt of charged particles trapped in space by the Earth's magnetic field.

[8] In December 1993, the Akeno Giant Air Shower Array in Japan (abbreviated AGASA) recorded one of the highest energy cosmic ray events ever observed.

[9] In October 2003, the Pierre Auger Observatory in Argentina completed construction on its 100th surface detector and became the largest cosmic-ray array in the world.

[9] It detects cosmic rays through the use of two different methods: watching Cherenkov radiation made when particles interact with water, and observing ultraviolet light emitted in the Earth's atmosphere.

Shower detection
Cherenkov radiation (light) glowing in the core of a nuclear reactor. In comparison to this, the camera has captured a blue light from this effect in the water from the radiation given off by reactor, the cosmic-ray observatories look for this radiation coming from cosmic-rays in Earth's atmosphere