Advanced Telescope for High Energy Astrophysics

The Advanced Telescope for High ENergy Astrophysics (ATHENA) is a future X-ray telescope of the European Space Agency, under development for launch around 2031. 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—the 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. The mission has its roots in two mission concepts from the early 2000s, for the ESA XEUS and NASA Constellation-X missions. In around 2008, these two proposals were merged into the joint NASA/ESA/JAXA International X-ray Observatory (IXO) proposal. However, in 2011 NASA withdrew from IXO due to funding issues, mainly due to large cost overruns on JWST. ESA then decided to proceed with a less costly modification of IXO, which became known as ATHENA. ATHENA was shortlisted for the first (L1) L-class Cosmic Vision selection in 2012, but lost to the Jupiter Icy Moon Explorer; after some modifications ATHENA was selected in 2014 as the second (L2) mission. The final decision about rebooting the International X-ray Observatory took place on 27 June 2014. The selected science topic is 'Hot and Energetic Universe' with an objective of answering two questions from astrophysics: The science team was appointed on 16 July 2014. Initial vibration testing of a silicon pore optics mirror module took place in August 2014. ESA's Science Programme Committee will meet in 2019 for a full review and final approval of the project before construction to begin in the same year. An Ariane 6 launch vehicle will lift ATHENA in 2031 into a large amplitude halo orbit around L2 point of the Sun-Earth system through a direct transfer burn. L2 was selected due to its stable thermal environment, good sky visibility and high observing efficiency. ATHENA is planned to perform scheduled observations of up to 300 celestial locations per year, each lasting from half an hour up to 11 days, though it can be repointed to observe transient events. ATHENA will utilise a telescope with 12 m focal length, and two primary instruments: high resolution X-ray Integral Field Unit (X-IFU), and the Wide Field Imager (WFI) featuring a moderate resolution and a large field of view. The telescope will use ESA-developed silicon pore optics providing combination of large field of view and high angular resolution. Each pore is a Wolter Type-I telescope only few mm2 in cross-section, with two reflections inside of each pore bringing X-ray in focus. In total, 1.5 million pores will be used. The telescope will be manufactured in 60 mm-wide arrays using commercially available silicon wafers.