The Pirs module of the Russian International Space Station (ISS) segment will be sunk in the ocean on Saturday, the Russian space agency, Roscosmos, told TASS on Thursday.
"Rocket space industry specialists analyzed the data received from the Nauka module’s remote reading and decided to schedule the sinking of the Pirs module (SO1) for July 24," the agency underlined.
Pirs was launched to the ISS on September 15, 2001 from the Baikonur Cosmodrome.
The Pirs module is currently docked to the Zvezda service module’s nadir port. It is planned that after Pirs is detached it will be replaced by the Nauka multipurpose scientific module which was launched from Baikonur on Wednesday.
Pirs undocking and deorbit scheduled for July 25
As a result of the flight control group operational meeting at the TsNIIMash Mission Control Center (part of Roscosmos), the specialists decided to adjust the plans to undock and deorbit the Pirs module.
The decision came based on the telemetry data and the need to build optimal orbit conditions. The operations are currently scheduled for Monday 26 July, 2021.
On Saturday, Roscosmos cosmonauts Oleg Novitskiy and Pyotr Dubrov closed the transfer hatches between the Pirs module and the Russian segment of the International Space Station, and checked them for pressure integrity. The physical separation is preliminary scheduled at 10:56 UTC on July 26, the non-combustible structural elements of the module and the ship are to drop in the Pacific Ocean at 14:51 UTC of the same day.
The Pirs docking module is now docked to the nadir port of the Zvezda Service Module of the Russian segment of the International Space Station. It is planned that after undocking it will be replaced by the Nauka Multipurpose Laboratory Module, which was launched from the Baikonur Cosmodrome on Wednesday and is currently in autonomous flight.
Prior to that, the Aist-2D small remote sensing spacecraft, developed at the Progress Rocket and Space Center (Samara, part of Roscosmos), photographed the International Space Station. RSC Progress is the operator of the Aist-2D satellite, providing control, reception, processing and distribution of the received information of remote sensing of the Earth.
Russia discards Pirs docking port to clear way for new ISS module
Russia's Pirs docking compartment, attached to the Progress MS-
For nearly 20 years, Russia's Pirs docking compartment served as one of the primary ports for vehicles arriving and departing from the International Space Station. On Monday (July 26), though, it was the module's turn to go to make way for a long-awaited, incoming upgrade.
The Pirs docking compartment undocked from the space station at 6:55 a.m. EDT (1055 GMT) and was slowly pulled away by the last Progress cargo spacecraft to dock to it. The departure, from the nadir, or Earth-facing side of the Zvezda service module on the station's Russian segment, marked the first major component of the orbiting complex to be decommissioned and discarded.
The 16-foot-long by 8-foot-diameter (5-by-2.5-m) Pirs, linked to the Progress MS-16 (77P) spacecraft, backed away from the station under the control of the cargo craft's engines. The uncrewed freighter was scheduled to perform a deorbit burn at 10:01 a.m. EDT (1401 GMT), sending it and Pirs back to Earth to be destroyed on their re-entry over the Pacific Ocean about four hours after they left the station.
The disposal came five days after Roscosmos, Russia's state space corporation, launched Pirs' replacement: the multipurpose laboratory module (MLM) named "Nauka" (the Russian word for "science"). Delayed by more than 13 years due to a series of technical issues and budget constraints, Nauka will serve as a research facility, docking port and spacewalk airlock.
The new module, which is based on the design of the station's Zarya functional cargo block (FGB), is scheduled to dock to the Pirs-vacated port on the Zvezda service module on July 29 at 9:25 a.m. EDT (1325 GMT). Russian flight controllers had originally planned for Pirs to undock on Thursday (July 22), but delayed it four days to allow more time to ensure the Nauka MLM was operating in Earth orbit as needed to safely connect to the space station.
The Pirs docking compartment was launched from the Baikonur Cosmodrome in Kazakhstan on Sept. 14, 2001, with a modified Progress as the upper stage of its Soyuz-U rocket. Three days later, it linked up with Zvezda, becoming the sixth pressurized module to be added to the space station.
Over the past 20 years, more than 70 vehicles docked and undocked from Pirs (which means "pier" in Russian). In total, 39 Progress cargo vehicles and 32 Soyuz crewed spacecraft used Pirs to arrive or depart from the space station.
The first use of Pirs as a docking port was by Soyuz TM-32 on Oct. 19, 2001. ISS Expedition 3 crewmates Vladimir Dezhurov and Mikhail Tyurin of Roscosmos, together with astronaut Frank Culbertson of NASA relocated the Soyuz from the nadir port on the Zarya FGB to Pirs.
Pirs was also used an airlock, supporting 53 spacewalks by pairs of cosmonauts and astronauts wearing Russian Orlan spacesuits. The first extravehicular activity (EVA) out of Pirs, conducted by Dezhurov and Tyurin on Oct. 8, 2001, marked the 100th Russian spacewalk in history.
The final use of Pirs as an airlock occurred on May 29, 2019, supporting an EVA by Expedition 59 crewmates Oleg Kononenko and Alexey Ovchinin. Subsequent Russian spacewalks were performed using the Poisk ("Search") mini-research module to prepare for Pirs' departure by removing exterior mounted experiments, repositioning antennas and re-routing cables.
In total, the Pirs docking compartment had been docked to the International Space Station for 19 years, 313 days, 9 hours, 50 minutes and 45 seconds. From the point of its launch to its expected destructive reentry was 19 years, 315 days, 15 hours, 10 minutes and 56 seconds.
In addition to the soon-to-arrive Nauka, the Russian segment of the station has three other available docking ports: mini-research modules Rassvet ("First Light") and Poisk, as well as the aft port on the Zvezda service module. U.S. commercial crew and cargo spacecraft connect to international docking adapters or are linked to common berthing mechanisms on U.S. operating segment connecting nodes.
The Pirs docking compartment, backdropped by the Zvezda service module, is seen at the International Space Station in 2001. (NASA)