Russian cosmonauts Oleg Kononenko and Sergei Prokofyev have completed their spacewalk on Wednesday more than an hour behind schedule, TASS reported.
"The cosmonauts successfully completed procedures envisaged by the program and returned to the space station, closing the exit hatch," a Mission Control Center official told TASS.
The cosmonauts began their spacewalk at 19:33 Moscow time on Tuesday and were expected to spend six hours and 31 minutes in space. However, they completed their objectives more than an hour behind schedule.
Congratulations from Rogozin
The head of Russia’s state corporation Roscosmos, Dmitry Rogozin, congratulated the cosmonauts on the success of their mission, describing the spacewalk as "unprecedented in terms of complexity and risks."
"I would like to congratulate you on successfully completing the mission. The spacewalk itself, I would say, was unprecedented in terms of complexity and risks. You coped with it with huge success," he said.
The Roscosmos head said the samples, taken during the spacewalk were "extremely important for completing all investigative procedures and establishing the causes of the spacecraft’s damage."
Rogozin also thanked the Russian Mission Control Center personnel for their efforts and NASA for its "informational and moral support."
What was done
The spacewalk’s main task was to inspect the hole on the external surface of the habitation module of the Soyuz MS-09 spacecraft, unsealing thermal insulation and the meteorite shield in the spot determined by the crew as lacking air tightness and examining the area for signs of sealant.
The hole had to be examined in space, because it was located in the section of the spacecraft that would separate during the reentry and burn in the atmosphere, making further investigation impossible.
It was the first time in the history of cosmonautics when the meteorite shield was opened during a space flight.
During their mission, Kononenko and Prokopyev cut open the thermal insulation and the meteorite shield, inspected them and made a photo of the hole in the habitation module. They also scraped off samples from the hole’s surface and removed small parts of the meteorite shield supposed to have signs of drilling on them. Later, they will send them to Earth for further studies aboard the same Soyuz MS-09 spacecraft.
Kononenko and Prokofyev did not have time to perform two scientific operations outside the ISS.
Besides, the Mission Control Center instructed them not to patch the Soyuz hull with new thermal insulation material, as was initially expected.
Soyuz hull damage
On August 30, a drop in air pressure was registered on the ISS. The crew examined the compartments and add-on modules one by one to identify a two-millimeter hole in the hull of the Soyuz MS-09 spacecraft attached to the orbital outpost. In the evening of the same day it was patched up with several layers of epoxy resin. Pressure returned to normal. On August 31 the crew reinforced the patch with another layer of sealant.
Shortly after, experts on the ground came to the conclusion that the hole was drilled from the inside of the spacecraft. It is yet unclear whether it was damaged on the ground or by someone from the ISS crew. In both cases, neither a deliberate action nor accidental damage has yet been ruled out.