A cosmic-ray observatory is a scientific installation built to detect high-energy-particles coming from space called cosmic rays. This typically includes photons (high-energy light), electrons, protons, and some heavier nuclei, as well as antimatter particles. About 90% of cosmic rays are protons, 9% are alpha particles, and the remaining ~1% are other particles. Methods of detection for gamma-rays: * Scintillation detectors * Solid state detectors * Compton scattering * Pair telescopes * Air Cherenkov detectors