The scientific spacecraft “Spectrum-Roentgen-Gamma” (Spectr-RG or SRG) is an X-ray observatory.  SRG’s main scientific goal is to chart an unprecedented map of the Universe in  X-rays on which all large clusters of galaxies will be marked.

Visit also main SRG portal at srg.cosmos.ru

Mapping the large-scale structure of the Universe is much like a time travel into the past. This map will be essential to solve the core questions of modern cosmology: How do dark energy and dark matter affect formation of the large-scale structure of the Universe? What is cosmological evolution of supermassive black holes? Spektr-RG is expected to find about 100,000 massive clusters of galaxies during the four-year survey mode, which means literally all such objects in the observable Universe. Furthermore, it will detect around three million supermassive black holes in active galactic nuclei (AGN), along with hundreds of thousands of stars with active coronae and accreting white dwarfs, tens of thousands of galaxies with active star formation. There might even be other objects of unknown nature. Spektr-RG will also study the hot interstellar and intergalactic medium, which is a source of bright X-ray emission.

The Spektr-RG astrophysical space observatory is developed by the Russian side under the Federal Space Program of Russia, section on Fundamental Space Research, by order of the Russian Academy of Sciences with the participation of Germany.  The SGR platform was constructed by the NPO Lavochkin.

Artist’s impression of theSpectr-RG”  (c) Roscosmos/DLR/СРГ

The main scientific goals of «Spectr-RG»

  • The first all-sky survey with an imaging telescope in the 0.5-11 keV band and the first all-sky imaging X-ray time variability survey.
  • Follow-up pointed observations of selected sources with high sensitivity in 3-axis stabilized regime in up to 30 keV energy range.

Spacecraft properties

1 Launch date 13.07.2019
2 Launch site Baikonur 81, Kazakhstan
3 Launcher Proton-M launch vehicle with Upper Stage DM-03
4 Reference system the second Lagrange point (L2) of the Sun-Earth system.
5 Expected lifetime 6,5 year
6 Spacecraft wet mass 2712,5 kg
7 Scientific payload mass 1210 kg
8 RF line band
9 Science data transmission rate 512 Kbit/s
10 Science equipment power 1805 W
Scheme of the “Spektr-RG” telescope with deployed solar panels. Full width 13.8 m (c) Roscosmos / DLR / SRG

The scientific payload consists of two independent telescopes — a soft-X-ray survey instrument, eROSITA, being provided by Germany, and a medium-X-ray-energy survey instrument,  ART-XC (Astronomical Roentgen Telescope- X-ray Concentrator), being developed by Russia. Both exploit the principles of grazing incidence imaging X-ray optic. To be reflected, X-ray photons must hit the mirror surface at a very small angle. Hence, X-ray mirrors are very oblong and tube-like. To increase the number of photons registered, several mirrors of ever increasing diameters are nested one into the other. Thus, one module consists of several mirror shells, and both telescopes consist of 7 modules each, with high-performance X-ray detectors placed in each focal point.  The SGR spacecraft is based on the “Navigator” multi-use bus adapted for the tasks of the project. Navigator platform is developed as the baseline module for key systems adaptable for various payloads and orbits. Navigator is a flight qualified platform. The Spektr-R highly elliptical spacecraft (launched in 2011) and two hydrometeorological Elektro-L geostationary satellites (launched in 2011, 2015) were built on this platform. This platform is developed by the NPO Lavochkin Scientific Production Association (Russia).

Observing strategy

  • ~3 months flight to L2 will be used in the verification and calibration of the payload.
  •  4 years – duration of an all sky survey 0.3-11 keV energy band; 8 all sky surveys (scanning mode: 6 rotations/day, 1 degree advance per day). Suspended. Starting on February 26, 2022, under the decision of German side, SRG/eROSITA X-ray telescope was switched to a safe mode. Since early March 2022 Russian Mikhail Pavlinsky ART-XC telescope operates under a new observational program
  • 2,5 years — follow-up pointed observations of  selected objects and regions in the harder X-ray range up to30 keV in a 3-axis stabilization mode.
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The orbit of SRG (c) Roscosmos/DLR/SRG

Operation Orbit

Halo orbit around Sun-Earth L2 outer Lagrange point, about 1.5 million kilometers from Earth. Orbital period around L2 is about 6 months. Maximum distance from ecliptic plane is 400,000 km. L2 is almost ideal for surveys. Spinning around its axis, the observatory will be able to map the whole celestial sphere in half a year. As the axisis pointed approximately to both Sun and Earth, the Sun itself does not enter the field of view. This means that eight all-sky surveys will be carried out in the first four years of operation. The technical challenge is to keep the spacecraft in orbit; therefore, periodical correcting maneuvers are envisaged.
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The head unit composition (c) Roscosmos / DLR / SRG

International collaboration

Leading organizations

  • from the Russian side for scientific payload: IKI RAS
  • from the Russian side for space and ground segment (except for scientific payload): Lavochkin Association
  • from the German side for eROSITA telescope: MPE
  • Mission Scientific Leader from the Russian side: Acad. Rashid Sunyae
  • eROSITA telescope Principal Investigator from the German side: Dr. Peter Predehl

Project Pages