The Russian segment of the International Space Station is now ready to receive the Nauka module, following the successful removal of the Pirs docking station and Progress spacecraft.
At 6:55 a.m. on Monday, July 26, an uncrewed Progress MS-16 transport cargo vehicle, along with the Pirs docking station, undocked from the ISS, according to a NASA statement. Both should have been mostly destroyed during a controlled re-entry through Earth’s atmosphere, and Russian space agency Roscosmos tweeted that the “non-combustible structural elements” of the craft fell into the Pacific Ocean.
The Progress 77 mission arrived at the ISS in February, delivering supplies and cargo to the Expedition 65 crew. The Pirs module has been in service for 20 years, having been launched to the station on September 14, 2001. Pirs, which means “pier” in Russian, is being decommissioned to make room for the incoming Nauka module, also known as the Multipurpose Laboratory Module (MLM), which was launched to orbit last Wednesday.
The original plan was to undock Pirs on Friday, July 23, but this was moved to Monday after a stream of problems with the Nauka mission, launched on July 21 from the Baikonur Cosmodrome in Kazakhstan. In addition to not completing its first orbit-raising burn (an issue resolved with backup thrusters), Nauka has an apparent antenna problem, and there’s something funky going on with its docking target, which could present difficulties on docking day, scheduled for Thursday, July 29.
This past Saturday, once it became clear that Nauka would reach the ISS, Roscosmos cosmonauts Oleg Novitskiy and Pyotr Dubrov began preparations for the undocking, closing the transfer hatches between Pirs and the Russian segment of the space station, while also checking them for pressure integrity, according to Roscosmos.
The Pirs docking station measures 16 feet long (4.9 meters) and 8.4 feet wide (2.6 meters) and weighs 8,461 pounds (3,838 kg), according to NASA. For the past two decades, the module has served as a science lab, docking port, and airlock for spacewalks.
Following the undocking, the module and spacecraft were moved to a safe distance. Controllers used Progress’s thrusters to slow the objects down, in a procedure that occurred at 10:01 a.m. EDT. What was left after reentry into Earth atmosphere fell into “a non-navigable area of the Pacific Ocean,” according to Roscosmos.
With Pirs and Progress gone, the port on the Earth-facing side of the Russian segment is ready to receive Nauka, which means “science” in Russian. The new segment will provide more room for science experiments, cargo, and equipment. Nauka is also delivering Europe’s new robotic arm, which will service the Russian segment of the space station.