Advanced Telescope For High ENergy Astrophysics

Advanced Telescope for High-ENergy Astrophysics (''Athena'') is an X-ray observatory mission selected by European Space Agency (ESA) within its Cosmic Vision program to address the Hot and Energetic Universe scientific theme. ''Athena'' will operate in the energy range of 0.2–12 keV and will offer spectroscopic and imaging capabilities exceeding those of currently operating X-ray astronomy satellites – e.g. the Chandra X-ray Observatory and XMM-Newton – by at least one order of magnitude on several parameter spaces simultaneously.

Mission

The primary goals of the mission are to map hot gas structures, determine their physical properties, and search for supermassive black holes.

History and development

The mission has its roots in two concepts from the early 2000s, XEUS of ESA and Constellation-X Observatory (Con-X) of NASA. Around 2008, these two proposals were merged into the joint NASA/ESA/JAXA International X-ray Observatory (IXO) proposal. In 2011, IXO was withdrawn and then ESA decided to proceed with a cost-reduced modification, which became known as ATHENA. ''Athena'' was selected in 2014 to become the second (L2) L-class Cosmic Vision mission, addressing the Hot and Energetic Universe science theme.

The scientific advice for the ''Athena'' mission is provided by the ''Athena'' Science Study Team (ASST) composed of expert scientists from the community. The ASST was appointed by ESA on 16 July 2014. The ESA Study Scientist and Study Manager are Dr Matteo Guainazzi and Dr Mark Ayre respectively. ''Athena'' completed successfully its Phase A with the Mission Formulation Review on 12 November 2019.

In 2023, the mission was rescoped as NewAthena. The next key milestone will be the mission adoption by ESA's Science Programme Committee (SPC) expected in 2027, leading to launch in 2037.

Orbit

In 2035, an Ariane 64 launch vehicle will lift ''Athena'' into a large amplitude halo orbit around the point of the Sun-Earth system. The orbit around was selected due to its stable thermal environment, good sky visibility, high observing efficiency, and stable particle background. ''Athena'' will perform pre-planned scheduled observations of up to 300 celestial locations per year. A special Target of Opportunity mode will allow a re-point manoeuvre within 4 hours for 50% of any randomly occurring events in the sky.

Optics and instruments

The ''Athena'' X-ray observatory consists of a single X-ray telescope with a 12 m focal length, with an effective area of approx. 1.4 m² (at 1 keV) and a spatial resolution of 5 arcseconds on-axis, degrading gracefully to less than 10 arcseconds at 30 arcminutes off-axis. The mirror is based on ESA's Silicon Pore Optics (SPO) technology. SPO provides an excellent ratio of collecting area to mass, while still offering a good angular resolution. It also benefits from a high technology readiness level and a modular design highly amenable to mass production necessary to achieve the unprecedented telescope collecting area. A movable mirror assembly can focus X-rays onto either one of ''Athena'' two instruments (WFI and X-IFU, see below) at any given time.

Both the WFI and X-IFU successfully passed their Preliminary Requirements Reviews, on 31 October 2018 and 11 April 2019 respectively.

Wide Field Imager (WFI)

The Wide Field Imager (WFI) is a large field of view spectral-imaging camera based on the uniqu
Silicon DEPFET technology
developed in the semiconductor laboratory of the Max Planck Society. The DEPFETs provide an excellent energy resolution (<170eV at 7keV), low noise, fast readout and high time resolution, with good radiation hardness. The instrument combines the Large Detector Array, which is optimized for a wide field of view observations over a 40' x 40' instantaneous sky area, with a separate Fast Detector tailored to observe the brightest point sources of the X-ray sky with high throughput and low pile-up. These capabilities, in combination with the unprecedented effective area and wide field of the ''Athena'' telescope, will provide breakthrough capabilities in X-ray imaging spectroscopy.

The WFI is developed by an international consortium composed of ESA member states. It is led by the Max Planck Institute for Extraterrestrial Physics (DEU) with partners in Germany (ECAP, IAA Tübingen), Austria (University of Vienna), Denmark (DTU), France ( CEA Saclay, Strasbourg), Italy (INAF, Bologna, Palermo), Poland (SRC PAS, NCAC PAS), the United Kingdom (University of Leicester, Open University), the United States (Pennsylvania State University (Penn State), SLAC, Massachusetts Institute of Technology (MIT), SAO), Switzerland (University of Geneva), Portugal (IA), and Greece (Athens Observatory, University of Crete). The principal investigator is Prof. Kirpal Nandra, Director of the High-Energy Group at MPE.

X-ray Integral Field Unit (X-IFU)

The X-ray Integral Field Unit is the cryogenic X-ray spectrometer of ''Athena'' X-IFU will deliver spatially resolved X-ray spectroscopy, with a spectral resolution requirement of 2.5 eV up to 7 keV over a hexagonal field of view of 5 arc minutes (equivalent diameter). The prime detector of X-IFU is made of a large format array of Molybdenum Gold transition-edge sensors coupled to absorbers made of Au and Bi to provide the required stopping power. The pixel size corresponds to slightly less than 5 arc seconds on the sky, thus matching the angular resolution of the X-ray optics. 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. This is achieved by the addition of a second cryogenic detector underneath the prime focal plane array. This way non-X-ray events such as particles can be vetoed using the temporal coincidence of detecting energy in both detectors simultaneously. The focal plane array, the sensors and the cold front end electronics are cooled at a stable temperature less than 100 mK by a multi-stage cryogenic chain, assembled by a series of mechanical coolers, with interface temperatures at 15 K, 4 K and 2 K and 300 mK, pre-cooling a sub Kelvin cooler made of a 3He adsorption cooler coupled with a
Adiabatic Demagnetization Refrigerator
Calibration data are acquired along with each observation from modulated X-ray sources to enable the energy calibration required to reach the targeted spectral resolution. 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. The X-IFU will thus be able to observe very bright X-ray sources. 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. More than 50 research institutes are involved in the X-IFU consortium. The principal investigator of X-IFU is Dr Didier Barret, Director of research at the research institute in astrophysics and planetology of Toulouse ( IRAP-OMP, CNRS UT3-Paul Sabatier/CNES, France). Dr Jan-Willem den Herder ( SRON, The Netherlands) and Dr Luigi Piro (INAF-IAPS, Italy) are co-principal investigators of the X-IFU. CNES manages the project, and on behalf of the X-IFU consortium, is responsible for the delivery of the instrument to ESA.

''Athena'' science goals

The "Hot and Energetic Universe" science theme revolves around two fundamental questions in astrophysics: How does ordinary matter assemble into the large-scale structures that we see today? And how do black holes grow and shape the Universe? Both questions can only be answered using a sensitive X-ray space observatory. 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. ''Athena'' will perform very sensitive measurements on a wide range of celestial objects. 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. Among them are highly obscured and high-redshift (z≥6) AGN. Furthermore, ''Athena'' will be an X-ray observatory open to the whole astronomical community, poised to provide wide-ranging discoveries in almost all fields of modern astrophysics, with a large discovery potential of still unknown and unexpected phenomena. It represents the X-ray contribution to the fleet of large-scale observational facilities to be operational in the 2030s (incl. SKA, ELT, ALMA, LISA...).

The ''Athena'' Community Office

The ''Athena'' Science Study Team (ASST) established the ''Athena'' Community Office (ACO) to obtain support in performing its tasks assigned by ESA, and most especially in the ASST role as "a focal point for the interests of the broad scientific community". Currently, this community is formed by more tha
800 members spread around the world

The ACO is meant to become a focal point to facilitate the scientific exchange between the ''Athena'' activities and the scientific community at large, and to disseminate the ''Athena'' science objectives to the general public. The main tasks of the ACO can be divided into three categories:

* Organisational aspects and optimisation of the community efforts assisting the ASST in several aspects, as for instance helping to the promotion of ''Athena'' science capabilities in the research world, through Conferences & Workshops or supporting the production of ASST documents, including the White Papers identifying the scientific synergies of ''Athena'' with other observational facilities in the early 2030s
* Keep the ''Athena'' community informed on the status of the project with the regular release of th

, brief news, weekly news on the ''Athena'' web portal and in the social channels.
* Develop communication and outreach activities, of particular interest, are th

.

The ACO is led by th
Instituto de Física de Cantabria (CSIC-UC)
Further ACO contributors are the Université de Genève, Max Planck Institute for Extraterrestrial Physics (MPE) and L'Institut de Recherche en Astrophysique et Planétologie (IRAP).

See also

* Spektr-RG
* List of proposed space observatories
* Lynx X-ray Observatory, a proposed space telescope with greater angular resolution, sensitivity, and spectroscopic power
* XRISM, pathfinder mission for ''Athena''
* List of European Space Agency programmes and missions

References

External links

The ''Athena'' X-ray observatory: ''Community Support Portal''

''Athena'' on ESA Cosmic Vision website

''Athena'' mission proposal video on YouTube

The ''Athena'' Wide Field Imager website

The ''Athena'' X-ray Integral Field Unit website

X-IFU, unveiling the secrets of the hot and energetic Universe video on YouTube

Silicon pore optics mirror video

Silicon pore optics mirror animation

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