MOSCOW, December 26. /TASS/. The radiator on the Soyuz MS-22 spacecraft docked to the International Space Station (ISS) was ruptured by a particle from the external side and its nature is still unclear, Roscosmos Executive Director for Human Spaceflights Sergey Krikalyov said on Monday.

"As of now, the most probable cause is a rupture of the radiator caused by a particle. Its nature is not very clear yet, this is external mechanical damage," he said.

On December 15, a drop in pressure in the docked Soyuz MS-22 manned spacecraft’s external cooling loop was recorded as Russian cosmonauts were preparing for their scheduled spacewalk. A visual inspection of the spacecraft from the orbital outpost confirmed the coolant leak, which cancelled the spacewalk.

As the Russian space agency reported, Roscosmos flight controllers conducted a series of tests of the Soyuz MS-22 spaceship’s systems, including a test of its propulsion control system that involved short-term activation of its berthing and attitude thrusters. The tests revealed that there were no other faults found.

On December 18, the Soyuz MS-22 spacecraft’s external surface was inspected with the help of cameras aboard the space station. The analysis of the data transmitted to Earth helped detect a potential leak in the spacecraft’s instrumentation/equipment compartment. According to preliminary data, the damage could have been caused by a micrometeoroid or space debris striking the external cooling loop on the Soyuz MS-22 spacecraft’s instrumentation/equipment compartment.