P. Predehl✉(Max Planck Institute for Extraterrestrial Physics)R. Andritschke(Max Planck Institute for Extraterrestrial Physics)V. Arefiev(Space Research Institute)V. Babyshkin(Scientific and Production Association. S.A. Lavochkin)O. Batanov(Space Research Institute)W. Becker(Max Planck Institute for Extraterrestrial Physics)H. Böhringer(Max Planck Institute for Extraterrestrial Physics)A. Bogomolov(Space Research Institute)T. Boller(Max Planck Institute for Extraterrestrial Physics)K. Borm(University of Bonn)W. Bornemann(Max Planck Institute for Extraterrestrial Physics)H. Bräuninger(Max Planck Institute for Extraterrestrial Physics)M. Brüggen(Universität Hamburg)H. Brunner(Max Planck Institute for Extraterrestrial Physics)M. Brusa(University of Bologna)E. Bulbul(Max Planck Institute for Extraterrestrial Physics)M. Buntov(Space Research Institute)V. Burwitz(Max Planck Institute for Extraterrestrial Physics)W. Burkert(Max Planck Institute for Extraterrestrial Physics)N. Clerc(Centre National de la Recherche Scientifique)E. Churazov(Space Research Institute)D. Coutinho(Max Planck Institute for Extraterrestrial Physics)T. Dauser(Friedrich-Alexander-Universität Erlangen-Nürnberg)K. Dennerl(Max Planck Institute for Extraterrestrial Physics)V. Doroshenko(University of Tübingen)J. Eder(Max Planck Institute for Extraterrestrial Physics)V. Emberger(Max Planck Institute for Extraterrestrial Physics)T. Eraerds(Max Planck Institute for Extraterrestrial Physics)A. Finoguenov(Max Planck Institute for Extraterrestrial Physics)M. Freyberg(Max Planck Institute for Extraterrestrial Physics)P. Friedrich(Max Planck Institute for Extraterrestrial Physics)S. Friedrich(Max Planck Institute for Extraterrestrial Physics)M. Fürmetz(Max Planck Institute for Extraterrestrial Physics)A. Georgakakis(National Observatory of Athens)M. Gilfanov(Max Planck Institute for Astrophysics)S. Granato(Max Planck Institute for Extraterrestrial Physics)C. Grossberger(Max Planck Institute for Extraterrestrial Physics)A. Gueguen(Max Planck Institute for Extraterrestrial Physics)P. Gureev(Scientific and Production Association. S.A. Lavochkin)F. Haberl(Max Planck Institute for Extraterrestrial Physics)O. Hälker(Max Planck Institute for Extraterrestrial Physics)G. Hartner(Max Planck Institute for Extraterrestrial Physics)G. Hasinger(European Space Astronomy Centre)H. Huber(Max Planck Institute for Extraterrestrial Physics)L. Ji(University of Tübingen)A. v. Kienlin(Max Planck Institute for Extraterrestrial Physics)W. Kink(Max Planck Institute for Extraterrestrial Physics)F. Korotkov(Space Research Institute)I. Kreykenbohm(Friedrich-Alexander-Universität Erlangen-Nürnberg)G. Lamer(Leibniz Institute for Astrophysics Potsdam)I. Lomakin(Scientific and Production Association. S.A. Lavochkin)I. Lapshov(Space Research Institute)T. Liu(Max Planck Institute for Extraterrestrial Physics)C. Maitra(Max Planck Institute for Extraterrestrial Physics)N. Meidinger(Max Planck Institute for Extraterrestrial Physics)B. Menz(Max Planck Institute for Extraterrestrial Physics)A. Merloni(Max Planck Institute for Extraterrestrial Physics)T. Mernik(Deutsches Zentrum für Luft- und Raumfahrt e. V. (DLR))B. Mican(Max Planck Institute for Extraterrestrial Physics)J. Mohr(Ludwig-Maximilians-Universität München)S. Müller(Max Planck Institute for Extraterrestrial Physics)K. Nandra(Max Planck Institute for Extraterrestrial Physics)V. Nazarov(Space Research Institute)F. Pacaud(University of Bonn)M. Pavlinsky(Space Research Institute)E. Perinati(University of Tübingen)E. Pfeffermann(Max Planck Institute for Extraterrestrial Physics)D. Pietschner(Max Planck Institute for Extraterrestrial Physics)M. E. Ramos-Ceja(Max Planck Institute for Extraterrestrial Physics)A. Rau(Max Planck Institute for Extraterrestrial Physics)J. Reiffers(Max Planck Institute for Extraterrestrial Physics)T. H. Reiprich(University of Bonn)J. Robrade(Universität Hamburg)M. Salvato(Max Planck Institute for Extraterrestrial Physics)J. Sanders(Max Planck Institute for Extraterrestrial Physics)A. Santangelo(University of Tübingen)M. Sasaki(Friedrich-Alexander-Universität Erlangen-Nürnberg)H. Scheuerle(Deutsches Zentrum für Luft- und Raumfahrt e. V. (DLR))C. Schmid(Friedrich-Alexander-Universität Erlangen-Nürnberg)J. Schmitt(Universität Hamburg)A. Schwope(Leibniz Institute for Astrophysics Potsdam)A. Shirshakov(Scientific and Production Association. S.A. Lavochkin)M. Steinmetz(Leibniz Institute for Astrophysics Potsdam)I. Stewart(Max Planck Institute for Extraterrestrial Physics)L. Strüder(Max Planck Institute for Extraterrestrial Physics)R. Sunyaev(Space Research Institute)C. Tenzer(University of Tübingen)L. Tiedemann(Max Planck Institute for Extraterrestrial Physics)J. Trümper(Max Planck Institute for Extraterrestrial Physics)V. Voron(Russian Federal Space Agency)P. Weber(Friedrich-Alexander-Universität Erlangen-Nürnberg)J. Wilms(Friedrich-Alexander-Universität Erlangen-Nürnberg)V. Yaroshenko(Max Planck Institute for Extraterrestrial Physics)
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.
