The Athena X-ray Integral Field Unit: A consolidated design for the system requirement review of the preliminary definition phase

Didier Barret (Corresponding Author), Vincent Albouys, Jan Willem den Herder, Luigi Piro, Massimo Cappi, Juhani Huovelin, Richard Kelley, J. Miguel Mas-Hesse, Stéphane Paltani, Gregor Rauw, Agata Rozanska, Jiri Svoboda, Joern Wilms, Noriko Yamasaki, Marc Audard, Simon Bandler, Marco Barbera, Xavier Barcons, Enrico Bozzo, Maria Teresa CeballosIvan Charles, Elisa Costantini, Thomas Dauser, Anne Decourchelle, Lionel Duband, Jean Marc Duval, Fabrizio Fiore, Flavio Gatti, Andrea Goldwurm, Roland den Hartog, Brian Jackson, Peter Jonker, Caroline Kilbourne, Seppo Korpela, Claudio Macculi, Mariano Mendez, Kazuhisa Mitsuda, Silvano Molendi, François Pajot, Etienne Pointecouteau, Frederick Porter, Gabriel W. Pratt, Damien Prêle, Laurent Ravera, Kosuke Sato, Joop Schaye, Keisuke Shinozaki, Konrad Skup, Jan Soucek, Mikko Kiviranta, Philippe Peille (Corresponding Author), CNES project team and the Consortium partners

Research output: Contribution to journalArticleScientificpeer-review

38 Citations (Scopus)


The Athena X-ray Integral Unit (X-IFU) is the high resolution X-ray spectrometer studied since 2015 for flying in the mid-30s on the Athena space X-ray Observatory. Athena is a versatile observatory designed to address the Hot and Energetic Universe science theme, as selected in November 2013 by the Survey Science Committee. Based on a large format array of Transition Edge Sensors (TES), X-IFU aims to provide spatially resolved X-ray spectroscopy, with a spectral resolution of 2.5 eV (up to 7 keV) over a hexagonal field of view of 5 arc minutes (equivalent diameter). The X-IFU entered its System Requirement Review (SRR) in June 2022, at about the same time when ESA called for an overall X-IFU redesign (including the X-IFU cryostat and the cooling chain), due to an unanticipated cost overrun of Athena. In this paper, after illustrating the breakthrough capabilities of the X-IFU, we describe the instrument as presented at its SRR (i.e. in the course of its preliminary definition phase, so-called B1), browsing through all the subsystems and associated requirements. We then show the instrument budgets, with a particular emphasis on the anticipated budgets of some of its key performance parameters, such as the instrument efficiency, spectral resolution, energy scale knowledge, count rate capability, non X-ray background and target of opportunity efficiency. Finally, we briefly discuss the ongoing key technology demonstration activities, the calibration and the activities foreseen in the X-IFU Instrument Science Center, touch on communication and outreach activities, the consortium organisation and the life cycle assessment of X-IFU aiming at minimising the environmental footprint, associated with the development of the instrument. Thanks to the studies conducted so far on X-IFU, it is expected that along the design-to-cost exercise requested by ESA, the X-IFU will maintain flagship capabilities in spatially resolved high resolution X-ray spectroscopy, enabling most of the original X-IFU related scientific objectives of the Athena mission to be retained. The X-IFU will be provided by an international consortium led by France, The Netherlands and Italy, with ESA member state contributions from Belgium, Czech Republic, Finland, Germany, Poland, Spain, Switzerland, with additional contributions from the United States and Japan.

Original languageEnglish
Pages (from-to)373-426
JournalExperimental Astronomy
Issue number2
Publication statusPublished - Apr 2023
MoE publication typeA1 Journal article-refereed


  • Athena: the advanced telescope for high energy astrophysics
  • Observatory
  • Space instrumentation
  • X-IFU: The X-ray Integral Field Unit
  • X-rays


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