The eROSITA X-ray telescope on SRG

¹ Max-Planck-Institut für extraterrestrische Physik, Gießenbachstraße, 85748 Garching, Germany
e-mail: predehl@mpe.mpg.de
² Universität Hamburg, Hamburger Sternwarte, Gojenbergsweg 112, 21029 Hamburg, Germany
³ Institut für Astronomie und Astrophysik, Abteilung Astronomie, Universität Tübingen, Sand 1, 72076 Tübingen, Germany
⁴ Universität Erlangen/Nürnberg, Dr.-Remeis-Sternwarte, Sternwartstraße 7, 96049 Bamberg, Germany
⁵ ESAC Camino bajo de Casillo s/n Villanueva de la Canada, Madrid, Spain
⁶ Ludwig-Maximilians-Universität München, Universitätssternwarte, Scheinerstraße 1, 81679 Munich, Germany
⁷ Leibniz Institut für Astrophysik Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany
⁸ Argelander-Institut für Astronomie, Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
⁹ IKI, Space Research Institute, 84/32 Profsouznaya ulitsa, Moscow 117997, Russian Federation
¹⁰ Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Straße, 85741 Garching, Germany
¹¹ Lavochkin Association, 24 Leningradskaya ulitsa, Khimki 141400, Moscow Region, Russian Federation
¹² Deutsches Zentrum für Luft- und Raumfahrt, Königswinterer Straße. 522-524, 53227 Bonn, Germany
¹³ National Observatory of Athens, V. Paulou & I. Metaxa, Athens, Greece
¹⁴ Institut de Recherche en Astrophysique et Planétologie (IRAP), Université de Toulouse, CNRS, UPS, CNES, 31028 Toulouse, France
¹⁵ Dipartimento di Fisica e Astronomia, Alma Mater Studiuorum Università di Bologna, Via Gobetti 93/2, 40129 Bologna, Italy
¹⁶ INAF – Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Gobetti 93/3, 40129 Bologna, Italy
¹⁷ State Space Corporation Roscosmos, 42 Schepkina ulitsa 42, Moscow 107996, Russian Federation

Received: 1 September 2020
Accepted: 23 September 2020

Abstract

eROSITA (extended ROentgen Survey with an Imaging Telescope Array) is the primary instrument on the Spectrum-Roentgen-Gamma (SRG) mission, which was successfully launched on July 13, 2019, from the Baikonour cosmodrome. After the commissioning of the instrument and a subsequent calibration and performance verification phase, eROSITA started a survey of the entire sky on December 13, 2019. By the end of 2023, eight complete scans of the celestial sphere will have been performed, each lasting six months. At the end of this program, the eROSITA all-sky survey in the soft X-ray band (0.2–2.3 keV) will be about 25 times more sensitive than the ROSAT All-Sky Survey, while in the hard band (2.3–8 keV) it will provide the first ever true imaging survey of the sky. The eROSITA design driving science is the detection of large samples of galaxy clusters up to redshifts z > 1 in order to study the large-scale structure of the universe and test cosmological models including Dark Energy. In addition, eROSITA is expected to yield a sample of a few million AGNs, including obscured objects, revolutionizing our view of the evolution of supermassive black holes. The survey will also provide new insights into a wide range of astrophysical phenomena, including X-ray binaries, active stars, and diffuse emission within the Galaxy. Results from early observations, some of which are presented here, confirm that the performance of the instrument is able to fulfil its scientific promise. With this paper, we aim to give a concise description of the instrument, its performance as measured on ground, its operation in space, and also the first results from in-orbit measurements.