The Development of Ground-Based Gamma-Ray Astronomy: A Historical Overview of the Pioneering Experiments

The ground-based technique for imaging atmospheric Cherenkov telescopes became a rapidly developing and powerful branch of science. Thanks to this technique, over 250 very high-energy gamma-ray sources of galactic and extragalactic origin have been discovered. Many fundamental questions of astrophysics, astro-particle physics, the physics of cosmic rays, and cosmology are the focus of this technique. In the past 33 years since the discovery of the first gamma-ray source, the Crab Nebula, the discipline has made remarkable progress. Today, the technology boasts highly sensitive telescopes capable of detecting a point source 100 times fainter than the standard candle, the Crab Nebula, in 25 h of observation. Further developments in this technology led to the Cherenkov Telescope Array (CTA), the next-generation large instrument. The sensitivity of CTA will be several times higher than that of the current best instruments. This chapter presents a brief history of ground-based very high-energy gamma-ray astrophysics.