Ground-based gamma-ray astronomy: history and development of techniques

TL;DR

This paper reviews the history, technological challenges, and current status of ground-based gamma-ray astronomy, highlighting its development as a key method for studying high-energy astrophysical phenomena.

Contribution

It provides a comprehensive historical overview and discusses recent advancements and future prospects in ground-based VHE gamma-ray detection techniques.

Findings

Ground-based gamma-ray astronomy has become a crucial high-energy astrophysics tool.

Technological challenges include atmospheric opacity and cosmic ray background discrimination.

Decades of development have refined Cherenkov detection methods.

Abstract

Very High Energy (VHE) gamma rays constitute one of the main pillars of high energy astrophysics. Gamma rays are produced under extreme relativistic conditions in the Universe. VHE gamma$ rays can be detected indirectly on the ground. Detection of these energetic photons poses several technological challenges. Firstly, even though gamma rays are highly penetrative, the Earth's atmosphere is opaque to them. Secondly, these gamma rays are to be detected against the overwhelming background of cosmic rays. When a VHE gamma ray arrives at the top of the atmosphere it produces charged secondaries. These charged particles produce Cherenkov flashes in the optical band. Even though the first attempts to detect these Cherenkov flashes were made almost 70 years ago, it took several decades of relentless efforts to streamline the technique. Ground-based VHE gamma-ray astronomy has now established itself as one of the crucial branches of conventional high energy astronomy to study the relativistic Universe. In this article we look back and present a historical perspective followed by a discussion on the current status and finally what lies ahead.