Two Russian cosmonauts have been removed from the next scheduled launch to the International Space Station "for medical reasons," according to the Russian space agency.
In a statement posted to its website on Wednesday (Feb. 19), Roscosmos said that Nikolai Tikhonov and Andrei Babkin will no longer fly to the space station in April, and will instead be replaced by backup crew members.
"The positions of the commander and flight engineer of the Soyuz MS-16 spacecraft will now be taken by Roscosmos cosmonauts Anatoli Ivanishin and Ivan Vagner," the agency said [In Russian] [roscosmos.ru]. "The changes will affect only the Russian part of the crew."
A NASA spokesperson confirmed that U.S. astronaut Chris Cassidy will continue to prepare for the mission, which will now see him, Ivanishin and Vagner serve as the Expedition 63 crew on board the space station.
Roscosmos provided few details about the medical concerns that led to the crew change. The agency's director of human spaceflight, former cosmonaut Sergei Krikalev, said in a news briefing that the issue involved one of the two replaced crew members.
"Due to personal data, we will not disclose it yet," said Krikalev, according to the Interfax news agency.
Russian media reports, citing unnamed sources, said that it was Tikhonov who had suffered an injury. Roscosmos appeared to support that by confirming that Babkin, along with cosmonaut Sergey Ryzhikov, had been reassigned as the new Soyuz MS-16 backup crew members.
Ivanishin, Vagner and Cassidy are scheduled to launch on April 9 atop a Soyuz-2.1a booster from Site 31 at Russia's Baikonur Cosmodrome in Kazakhstan. It will be the first spaceflight for Vagner and the third for both Ivanishin and Cassidy.