GRAPES-3 (Gamma Ray Astronomy PeV EnergieS 3rd establishment) is a project for cosmic ray study with air shower detector array and large area muon detectors at Ooty in southern India. Its targets are to study about nuclear composition of cosmic ray, high energy gamma-ray astronomy and modulation of solar activity.
GRAPES-3 is collaborative project between India and Japan. It is located at Ooty in Tamilnadu of southern India (N11.4o, E76.7o, H2200m a.s.l.). It started to observe air showers with 217 scintillators and 560 m² of muon detector in 2000. A scintillator can detect charged particles of showers. They are covered on about 10,000 m² area. Muon detectors can detect muon whose energy is above 109 eV.