Cosmic ray sources and detectors

Abstract The origin of cosmic rays has remained an enduring mystery in astrophysics since their discovery by Victor Hess in 1912. However, extensive studies on the energy spectrum, mass composition, and angular distributions of cosmic rays have been conducted through both space-based and ground-based experiments. Although space-based experiments are limited to measuring cosmic rays with energies below about 10 $$^{14}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mmultiscripts> <mml:mrow/> <mml:mrow/> <mml:mn>14</mml:mn> </mml:mmultiscripts> </mml:math> eV, their high precision has led to the discovery of several new features in the cosmic ray spectrum. However, ground-based detector arrays have provided valuable insights into cosmic rays at higher energies, offering new information on their spectrum, composition, and angular distributions. This paper reviews the major cosmic ray detectors currently in operation, both in space and on the ground, followed by an in-depth look at the GRAPES-3 experiment, which operates in Ooty, India, and focuses on the TeV-PeV energy range. Recent findings from GRAPES-3 on the cosmic ray spectrum and anisotropy are discussed, along with an update on the ongoing upgrade of the experiment.