The Proton-M launch vehicle with the Spektr-RG observatory is preparing to start from the Baikonur.
The Russian-German project aims to chart the first all-sky map of the Universe in order to shed light on the fundamental problems of cosmology and physics of supermassive black holes.
The State Commission decided to postpone the launch date of the Proton-M launch vehicle with the DM-03 upper stage and the Spektr-RG space observatory to a reserve date (on June 22 or July 12 and 13.).
Original article of the ROSCOSMOS group (in Rus).
(18 June 2019 – DLR) On 21 June 2019 the Spektrum-Röntgen-Gamma (Spektr-RG / SRG) spacecraft will be launched from the Kazakh steppe, marking the start of an exciting journey.
SRG will be carrying the German ‘extended ROentgen Survey with an Imaging Telescope Array’ (eROSITA) X-ray telescope and its Russian ART-XC partner instrument. A Proton rocket will carry the spacecraft from the Baikonur Cosmodrome towards its destination – the second Lagrange point of the Sun-Earth system, L2, which is 1.5 million kilometres from Earth. In orbit around this equilibrium point, eROSITA will embark upon the largest ever survey of the hot Universe.
The German X-ray telescope eROSITA and its Russian partner instrument ART-XC are installed on the Navigator platform. The Navigator platform supplies the Spektrum-Röntgen-Gamma spacecraft with power, sends the collected data to Earth and provides attitude and orbit control. (courtesy: Roscosmos/DLR/SRG/Lavochkin)
The first core component of the eROSITA space telescope consists of seven identical mirror modules aligned in parallel. Each has a diameter of 36 centimetres and consists of 54 nested mirror shells whose surface is composed of a paraboloid and a hyperboloid (Wolter I optics). They collect high-energy photons and focus them onto the X-ray cameras. (courtesy: P. Friedrich/MPE)
The second core component of the telescope is the X-ray camera system. At the focal point of each mirror system is a highly sensitive CCD detector that was specially developed for eROSITA in the semiconductor laboratory at the Max Planck Society. These detectors are a further development of existing X-ray CCD cameras. (courtesy: P. Friedrich/MPE)
The space telescope will use its seven X-ray detectors to observe the entire sky and search for and map hot sources such as galaxy clusters, active black holes, supernova remnants, X-ray binaries and neutron stars. “eROSITA’s X-ray ‘eyes’ are the best that have ever been launched as part of a space telescope. Their unique combination of light-collecting area, field-of-view and resolution makes them approximately 20 times more sensitive than the ROSAT telescope that flew to space in the 1990s. ROSAT also incorporated advanced technology that was ‘made in Germany’.
With its enhanced capabilities, eROSITA will help researchers gain a better understanding of the structure and development of the Universe, and also contribute towards investigations into the mystery of Dark Energy,” says Walther Pelzer, Executive Board Member for the Space Administration at the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR), which supported the development of eROSITA at the Max Planck Institute for Extraterrestrial Physics (MPE).
Dark Energy – a ‘cosmic fuel’ that is accelerating the expansion of the Universe
The Universe has been expanding continuously since the Big Bang. Until the 1990s, it was thought that this cosmic expansion would slow down and eventually come to a halt. Then, the astrophysicists Saul Perlmutter, Adam Riess and Brian Schmidt observed stellar explosions that were visible from a great distance and always emitted the same amount of light. They measured their distances and could hardly believe their findings. “The Type 1a supernovae observed exhibited lower brightness levels than expected. It was clear that the Universe was not slowing down as it expanded – quite the opposite, in fact. It is gathering speed and its components are being driven further and further apart at an ever-increasing rate,” explains Thomas Mernik, eROSITA Project Manager at the DLR Space Administration. With this discovery, the three researchers turned science upside and were awarded the Nobel Prize in Physics in 2011. Yet Perlmutter, Riess and Schmidt have left us with one crucial question: “What is the ‘cosmic fuel’ that powers the expansion of the Universe? Since no one has yet been able to answer this question, and the ingredients of this catalyst are unknown, it is simply referred to as Dark Energy. eROSITA will now attempt to track down the cause of this acceleration,” explains Mernik.
Galaxy clusters – a key to Dark Energy
Very little is known about the Universe. The ingredients that make up four percent of its energy density – ‘normal’ material such as protons and neutrons – is only a very small part of the ‘Universe recipe’. What the other 96 percent is composed of remains a mystery. Today it is believed that 26 percent is Dark Matter. However, the largest share, estimated at 70 percent, is comprised of Dark Energy. To track this down, scientists must observe something unimaginably large and extremely hot: “Galaxy clusters are composed of up to several thousand galaxies that move at different velocities within a common gravitational field. Inside, these strange structures are permeated by a thin, extremely hot gas that can be observed through its X-ray emissions. This is where eROSITA’s X-ray ‘eyes’ come into play. They allow us to observe galaxy clusters and see how they move in the Universe, and above all, how fast they are travelling. We hope that this motion will tell us more about Dark Energy,” explains Thomas Mernik.
Map of the entire hot Universe – the largest cosmic catalogue
Scientists are not just interested in the movement patterns of galaxy clusters. They also want to count and map these structures. Up to 10,000 such clusters should be ‘captured’ by eROSITA’s X-ray ‘eyes’ – more than have ever been observed before. In addition, other hot phenomena such as active galactic nuclei, supernova remnants, X-ray binaries and neutron stars will be observed and identified. eROSITA will scan the entire every six months for this purpose and create a deep and detailed X-ray map of the Universe over four years. This will make it possible for eROSITA to produce the largest-ever cosmic catalogue of hot objects and thus improve our scientific understanding of the structure and development of the Universe.
eROSITA – seven X-ray ‘eyes’ looking into the Universe
The German telescope consists of two core components – its optics and the associated detectors. The former consists of seven mirror modules aligned in parallel. Each module has a diameter of 36 centimetres and consists of 54 nested mirror shells, whose surface is composed of a paraboloid and a hyperboloid (Wolter-I optics). “The mirror modules collect high-energy photons and focus them onto the CCD X-ray cameras, which were specially developed for eROSITA at our semiconductor laboratory in Garching. These form the second core component of eROSITA and are located at the focus of each of the mirror systems. The highly sensitive cameras are the best of their kind and, together with the mirror modules, form an X-ray telescope featuring an unrivalled combination of light-collecting area and field-of-view,” explains Peter Predehl, eROSITA Principal Investigator at MPE.
Spektrum-Röntgen-Gamma – a space mission with numerous partners
Spektrum-Röntgen-Gamma (SRG) is a space mission with numerous partners. On the Russian side, it involves the space agency Roscosmos, the space company Lavochkin and the Space Research Institute of the Russian Academy of Sciences (IKI) . The German eROSITA X-ray telescope was developed and built by the Max Planck Institute for Extraterrestrial Physics (MPE) in Garching, in collaboration with the Leibniz Institute of Astrophysics in Potsdam (AIP) and the universities of Erlangen-Nuremberg, Hamburg and Tübingen with the support of the DLR Space Administration. Furthermore, the Universities of Munich and Bonn will participate in analysing eROSITA data. The partner institutes involved in the eROSITA telescope have created software for data analysis, mission planning and simulations, as well as components of the hardware. However the main responsibility lay with MPE. “As a rule, an instrument as complex as eROSITA can only be implemented by a major institute with the help of an industrial Prime Contractor. However, together with MPE, we took a different path and let the institute conduct the development work on its own,” says Thomas Mernik. The project management, product assurance and system design were key tasks performed by MPE itself. It also delegated other tasks to industry, such as the manufacturing of the mirrors, the structure, the thermal insulation, mechanical precision parts, electronics boards and much more. “Since eROSITA is about to embark on its journey into space, in retrospect we can say that this approach was very successful and sensible,” says Mernik.
Source: Space Newsfeed
A German–Russian mission called SRG will detect millions of supermassive black holes, many new to science, and hundreds of thousands of stars.
“Have you seen your body in X-rays? It looks completely different,” says Rashid Sunyaev. “We will do the same with the Universe.” Sunyaev, an eminent Soviet-born cosmologist at the Max Planck Institute for Astrophysics in Garching, Germany, could be about to get his long-held wish.
On 21 June, a joint German–Russian mission called Spectrum-Roentgen-Gamma (SRG) will launch into space to chart an unprecedented map. It won’t be the first space telescope sensitive to high-energy ‘hard’ X-rays, which offer astrophysicists a window into otherwise faint objects in the Universe. But it will be the first able to create a full map of the sky in this part of the spectrum — one that will give researchers a new way to track the Universe’s expansion and acceleration over the aeons. “Within a half year, we will cover the whole sky,” says Peter Predehl, an X-ray astronomer at the Max Planck Institute for Extraterrestrial Physics, also in Garching, and a principal investigator for the mission.
SRG’s main scientific goal is cosmological: to create a 3D map of the cosmos that will reveal how the Universe accelerates under the mysterious repulsive force called dark energy. Cosmologists can probe this force through galactic clusters, whose distribution encodes the structure and history of the Universe. SRG will map a cosmic web of about 100,000 galactic clusters by detecting the X-ray glow from their intergalactic plasma and from the plasma filaments that join them. The mission will also detect up to three million supermassive black holes — many of which will be new to science — and X-rays from as many as 700,000 stars in the Milky Way.
“It’s going to be a great survey,” says X-ray astronomer Giuseppina Fabbiano of the Harvard–Smithsonian Center for Astrophysics in Cambridge, Massachusetts. Its data will have a unique role in the field for a long time, she adds.
For Russia, SRG represents one of the most significant space-science missions for decades, and it aims to bolster the country’s astrophysics community, which has suffered decades of cuts and brain drain. The mission carries two independent X-ray telescopes: a German-built one called eROSITA (Extended Roentgen Survey with an Imaging Telescope Array) and a Russian-built one called ART-XC (Astronomical Roentgen Telescope — X-ray Concentrator), which is the first instrument of its kind in the history of Russian and Soviet space research, says Mikhail Pavlinsky, a high-energy astrophysicist at the Russian Academy of Sciences Space Research Institute in Moscow and principal investigator on ART-XC. “Now we have a new chance to return to world-class science,” he says.
The spacecraft will lift off on a Russian-built Proton-M rocket from the Baikonur Cosmodrome in Kazakhstan. X-ray sky surveys have been conducted by previous missions, including one from Germany in the 1990s, called ROSAT. But that mission was sensitive only to ‘soft’ X-rays, with energies of about 2 kiloelectronvolts (keV). Existing missions, such as NASA’s Chandra X-ray Observatory and NuSTAR, can see higher-energy radiation and resolve tiny details of cosmic structures, but they see only small parts of the sky.
SRG’s two instruments each cover X-ray bands that stretch to much higher energies: 0.2–10 keV for eROSITA, and 5–30 keV for ART-XC. (Despite its name — which was kept for historical reasons — SRG will not detect gamma radiation.) Each instrument is a bundle of seven X-ray telescopes that will frame the same swathe of sky simultaneously; their combined power means that they will collect more photons than a single telescope. X-ray photons from the sky are few and far between, so the telescopes’ semiconductor-based sensors — higher-energy versions of the sensors in ordinary digital cameras — will also be able to estimate the amount of energy contained in individual photons.
During its planned four-year mission, SRG will map the entire sky eight times, and researchers will compare the maps and look for changes. For instance, some of the supermassive black holes at galactic centres become extremely bright when they devour matter at a high rate, and then go back to relative quiescence. Although most soft X-rays from these black holes are likely to be absorbed by surrounding dust, harder X-rays should get through, says Pavlinsky. ART-XC might see the objects appearing and then disappearing again from one year to the next, providing information about how black holes consume matter. “We wish to observe several thousand of these events during these four years,” Sunyaev says.
SRG will also investigate the Universe’s distrubtion of ordinary matter and dark matter — the main engine of galaxy formation — and look for direct hints as to the nature of dark-matter particles. It will do this by trying to confirm previous signals that showed peaks in X-ray emissions from some galactic centres, which some researchers have suggested come from the decay of an unknown, heavier relative of the known subatomic particles called neutrinos. These neutrinos could be a major component of dark matter, they suggest — although this interpretation is controversial. “So far, the dark-matter explanation is still on the table” as a potential cause of the X-ray signal, says Esra Bulbul, an astrophysicist at the Max Planck Institute for Extraterrestrial Physics and a lead scientist on the mission.
A long time coming
A hard-X-ray space mission has long been on the cards for Russian and German astrophysicists: SRG’s roots stretch back to the Soviet Union. In 1987, leading astrophysicists including Sunyaev — with his mentor Yakov Zeldovich and Andrei Sacharov — proposed a major mission using hard X-rays, but plans were cancelled after the Soviet Union fell in 1991.
The European and Russian space agencies revived the idea in 2004, but a proposal to send an X-ray telescope to the International Space Station was scrapped when NASA whittled down its space-shuttle programme, ultimately ending it in 2011. The German space agency and Roscosmos later approved a joint mission, and more ambitious design in 2009.
“There have been many, many ups and down until the whole thing really came out of the woods,” says Predehl.
Unusually, the mission has special data arrangement that aims to support Russia’s small astrophysics community. Instead of putting the data in one repository, as is typical for such missions, German researchers will store and analyse data on one half of the sky (the part west of the Galactic Centre) and Russian scientists will do the same with the other half, giving them dedicated time to work on the data, says Sunyaev. The mission will later open the data to other researchers.