A joint Russian–German X-ray observatory due for launch in 2018 or later into a position at the L2 Lagrangian point of the Earth’s orbit. It will carry two imaging X-ray telescopes: eROSITA (extended ROentgen Survey with an Imaging Telescope Array) will observe at energies of 0.5–10 keV, while ART-XC (Astronomical Roentgen Telescope X-ray Concentrator) will observe at 6–30 keV.
http://hea.iki.rssi.ru/SRG/en/index.php Official mission website.
https://directory.eoportal.org/web/eoportal/satellite-missions/content/-/article/srg Information website with much background information.