Russia has announced it is pulling out of the International Space Station (ISS) in 2024 to focus on building its own low Earth orbit outpost.
Russia's space agency, Roscosmos, is one of five international space agencies that have had principal involvement with the ISS since its earliest development in 1993.
So what does that mean for the ISS and Russia's future involvement in space exploration?
Russia's history in space
Russia, and the Soviet Union, have been at the forefront of space station construction.
It was the USSR's Salyut program, which started in 1970, that eventually established the mechanism for continuous occupation of space stations via docking stations and modular construction of a station in space.
Those Salyut modules provided the template for the first modular space station, Mir, which was assembled, in orbit, in 1986.
Is this part of a new space race?
Absolutely.
During the Cold War, the USA and Soviet Union competed to achieve space flight capabilities.
The USSR had early success with the launch of Sputnik — the first successful satellite launch in 1957 — and Yuri Gagarin — the first human to go into space in 1961.
The USA upped the ante with the development of the Apollo program that delivered Neil Armstrong and Buzz Aldrin to the surface of the Moon in 1969.
While the Americans focused on the Moon landing, the Soviets turned their attention to their satellite program.
Was there US-Russian collaboration?
The USA and USSR had both expressed a tentative desire to work together through the 1960s, including the signing of the Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space.
This, among other things, aimed to ensure no single country would attempt to claim ownership over a celestial body, and to ban the placement of weapons of mass destruction into orbit.
Relations continued to thaw all the way up until the Apollo-Soyuz Test Project in 1975, when an American shuttled docked with a Soviet module in space, arguably ending the space race.
Was Mir a Russian-only space station?
The Soviet Union launched Mir, which had been in development since 1976, a decade later in 1986.
The US and Russian Federation signed a renewed agreement for cooperation in space in 1992.
This agreement resulted in Sergei Kirkalev becoming the first Russian cosmonaut to fly aboard a space shuttle in 1994.
A year later NASA astronaut Norman Thagard spent 115 days aboard Mir with his Russian counterparts.
It was the first time an American had been on the space station.
Between 1988 and 1999 several European astronauts also visited the station.
While Mir was in operation, the USA planned to develop its own space station called Freedom.
However, due to budget cutbacks, Freedom never made it further than the advanced planning stage.
The International Space Station
In 1993, NASA and Roscosmos met and decided to merge the Freedom project with the proposed Mir-2 station, creating the International Space Station.
Construction of the ISS in orbit started in 1998 and is run by five separate space agencies, with the USA and Russia joined by the European, Canadian and Japanese space agencies, which represent 15 different countries.
The ISS has been inhabited continuously for almost 22 years with a current crew of seven, consisting of three Americans, three Russians and an Italian.
The ISS is split into two sections, the US Orbital Segment and the Russian Orbital Segment, with international cooperation on board governed by a 1998 agreement.
NASA hopes the ISS will continue to operate until 2031, at which point it will be crashed into the Pacific Ocean.
However, the current agreement lapses in 2024, which is why Russia chose that date to pull out.
How did the war in Ukraine affect cooperation?
NASA and Roscosmos struck a deal earlier this month for American astronauts to continue riding Russian rockets to the ISS until 2024.
The agreement also allowed for Russian cosmonauts to catch lifts to the space station with SpaceX in the next few months.
AP reported that NASA and Roscosmos said the agreement ensured that the space station would always have at least one American and one Russian on board to keep both sides of the outpost running smoothly.
However, earlier this year, former director of Roscosmos, Dmitry Rogozin, criticised the US sanctions placed on Russia after the invasion as risking the competitiveness of the global space market and suggested a lack of cooperation would risk an unplanned re-entry of the space station.
So what's next?
Russia's plans to develop its own space station, the Russian Orbital Service Station.
That will join China's Tiangong space station, the country's first modular orbital space station, which is currently under construction.
China has never been a part of the International Space Station but has launched two precursor stations to its current version of the Tiangong.
