Advanced Telescope for High-ENergy Astrophysics (Athena)[1][2] is an X-ray observatory mission selected by European Space Agency (ESA) within its Cosmic Vision program[3] to address the Hot and Energetic Universe scientific theme.
The primary goals of the mission are to map hot gas structures, determine their physical properties, and search for supermassive black holes.
[4] Athena was selected in 2014 to become the second (L2) L-class Cosmic Vision mission,[5] addressing the Hot and Energetic Universe science theme.
The next key milestone will be the mission adoption by ESA's Science Programme Committee (SPC) expected in 2023[needs update], leading to launch in 2035.
[6] In 2035, an Ariane 64 launch vehicle will lift Athena into a large amplitude halo orbit around the L2 point of the Sun-Earth system.
A large part of the X-IFU related Athena science objectives relies on the observation of faint extended sources (e.g. hot gas in cluster of galaxies to measure bulk motions and turbulence or its chemical composition), imposing the lowest possible instrumental background.
Although an integral field unit where each and every pixel delivers a high resolution X-ray spectrum, the defocussing capability of the Athena mirror will enable the focal beam to be spread over hundreds of sensors.
It will do so either with the nominal resolution, e.g. for detecting the baryons thought to reside in the Warm Hot Intergalactic Medium, using bright gamma-ray burst afterglows, as background sources shining through the cosmic web, or with a spectral resolution of 3–10 eV, e.g. for measuring the spins and characterizing the winds and outflows of bright X-ray binaries at energies where their spectral signatures are the strongest (above 5 keV).
As of December 2018, when the X-IFU consortium was formally endorsed by ESA as being responsible for the procurement of the instrument to Athena, the X-IFU consortium gathered 11 European countries (Belgium, Czech Republic, Finland, France, Germany, Ireland, Italy, Netherlands, Poland, Spain, Switzerland), plus Japan and the United States.
The "Hot and Energetic Universe" science theme [18] revolves around two fundamental questions in astrophysics: How does ordinary matter assemble into the large-scale structures that we see today?
Its combination of scientific performance exceeds any existing or planned X-ray missions by over one order of magnitude on several parameter spaces: effective area, weak line sensitivity, survey speed, just to mention a few.
It will investigate the chemical evolution of the hot plasma permeating the intergalactic space in cluster of galaxies, search for elusive observational features of the Warm-Hot Intergalactic Medium, investigate powerful outflows ejected from accreting black holes across their whole mass spectrum, and study their impact on the host galaxy, and identify sizeable samples of comparatively rare populations of Active Galactic Nuclei (AGN) that are key to understanding the concurrent cosmological evolution of accreting black holes and galaxies.