Spektr-UV was expected to take off from the Vostochny spaceport atop an Angara A5M rocket after 2025.
"Experimental and development work on Spektr-UV is currently at the stage of the development of detailed design documentation, manufacturing spacecraft's components, and their ground-based experimental testing. The launch of the spacecraft is scheduled for the fourth quarter of 2028," Roscosmos said.
The agency said the contract for the development of the spacecraft had been signed for the period up to 2025. A new contract to continue the development of the spacecraft and its launch will be signed after Russia's new federal space program is approved in 2026.
The space telescope is being developed for studying explosive processes in galaxies, stellar and compact objects, the birth of stars and planetary systems, as well as processes occurring in the atmospheres of planets, comets, and other space objects of the solar system. The telescope would also observe discovered exoplanets to study their atmospheres and detect signs of life.
Lev Zelyony, the deputy chairman of the Space Council of the Russian Academy of Sciences, said earlier that Spektr-UV is very close to the Hubble Space Telescope, launched by the United States in 1990, and could take its place in the future.
Scientists from Spain and Japan were expected to take part in the project.
Earlier, the project's chief designer, Sergey Shostak, said that the participation of Japan and Spain in the development of Spektr-UV remained an open question, but the Astronomy Institute of the Russian Academy of Sciences has already worked out the replacement of elements of scientific instruments that these countries wanted to supply with domestic ones. However, on December 28, Roscosmos told Sputnik that Japanese and Spanish scientists have not yet officially abandoned participation in the development of the spacecraft.