The Advanced Telescope for High ENergy Astrophysics (ATHENA) is a planned X-ray telescope of the European Space Agency. It is the second (L2) large class mission within ESA Cosmic Vision Program. ATHENA will be one hundred times more sensitive than the best of existing X-ray telescopes—Chandra X-ray Observatory, and XMM-Newton. The primary goals of the mission are to map hot gas structures, determining their physical properties, and searching for supermassive black holes.