Given the question: Information: - China, officially the People's Republic of China (PRC), is a unitary sovereign state in East Asia. With a population of over 1.381billion, it is the world's most populous country. The state is governed by the Communist Party of China, and its capital is Beijing. It exercises jurisdiction over 22 provinces, five autonomous regions, four direct-controlled municipalities (Beijing, Tianjin, Shanghai, and Chongqing), and two mostly self-governing special administrative regions (Hong Kong and Macau), and claims sovereignty over Taiwan. The country's major urban areas include Shanghai, Guangzhou, Beijing, Chongqing, Shenzhen, Tianjin and Hong Kong. China is a great power and a major regional power within Asia, and has been characterized as a potential superpower. - Salyut 5 (meaning "Salute 5"), also known as OPS-3, was a Soviet space station. Launched in 1976 as part of the Salyut programme, it was the third and last Almaz space station to be launched for the Soviet military. Two Soyuz missions visited the station, each manned by two cosmonauts. A third Soyuz mission attempted to visit the station, but failed to dock, whilst a fourth mission was planned but never launched. - Vitaly Mikhaylovich Zholobov (born 18 June 1937) is a retired Soviet cosmonaut who flew on Soyuz 21 space flight as the flight engineer. - Human spaceflight (also referred to as manned spaceflight) is space travel with a crew or passengers aboard the spacecraft. Spacecraft carrying people may be operated directly, by human crew, or it may be either remotely operated from ground stations on Earth or be autonomous, able to carry out a specific mission with no human involvement. - The Almaz ("Diamond") program was a highly secretive Soviet military space station program, begun in the early 1960s. - Mir (; lit."peace" or "world") was a space station that operated in low Earth orbit from 1986 to 2001, run by the Soviet Union and later by Russia. "Mir" was the first modular space station and was assembled in orbit from 1986to1996. It had a greater mass than any previous spacecraft. At the time it was the largest artificial satellite in orbit, succeeded by the International Space Station after Mir's orbit decayed. The station served as a microgravity research laboratory in which crews conducted experiments in biology, human biology, physics, astronomy, meteorology and spacecraft systems with a goal of developing technologies required for permanent occupation of space. - The International Space Station (ISS) is a space station, or a habitable artificial satellite, in low Earth orbit. Its first component launched into orbit in 1998, and the ISS is now the largest artificial body in orbit and can often be seen with the naked eye from Earth. The ISS consists of pressurised modules, external trusses, solar arrays, and other components. ISS components have been launched by Russian Proton and Soyuz rockets, and American Space Shuttles. - Tiangong-2 is a Chinese space laboratory and part of the Project 921-2 space station program. Tiangong-2 was launched on 15 September 2016, 22:04:09 (UTC+8). - A low Earth orbit (LEO) is an orbit around Earth with an altitude between (orbital period of about 88 minutes), and (about 127 minutes). Objects below approximately will experience very rapid orbital decay and altitude loss. - Soyuz 5 ("Union 5") was a Soyuz mission using the Soyuz 7K-OK spacecraft launched by the Soviet Union on 15 January 1969, which docked with Soyuz 4 in orbit. It was the first-ever docking of two manned spacecraft of any nation, and the first-ever transfer of crew from one space vehicle to another of any nation, the only time a transfer was accomplished with a space walk two months before the US Apollo 9 mission performed the first ever internal crew transfer. - Tiangong-1 is China's first prototype space station, serving as both a manned laboratory and an experimental testbed to demonstrate orbital rendezvous and docking capabilities. Launched unmanned aboard a Long March 2F/G rocket on 29 September 2011, it is the first operational component of the Tiangong program, which aims to place a larger, modular station into orbit by 2023. Tiangong-1 was initially projected to be deorbited in 2013, to be replaced over the following decade by the larger Tiangong-2 and Tiangong-3 modules, but as of October 2016 it was still aloft, though in a decaying orbit. - A spacecraft is a vehicle, or machine designed to fly in outer space. Spacecraft are used for a variety of purposes, including communications, earth observation, meteorology, navigation, space colonization, planetary exploration, and transportation of humans and cargo. - Boris Valentinovich Volynov (born 18 December 1934) is a Soviet cosmonaut who flew two space missions of the Soyuz programme: Soyuz 5, and Soyuz 21. He was the first halakhic (by mother) Jewish cosmonaut. - The Soyuz programme (or meaning "Union") is a human spaceflight programme that was initiated by the Soviet Union in the early 1960s, originally part of a Moon landing project intended to put a Soviet cosmonaut on the Moon. It was the third Soviet human spaceflight programme after the Vostok and Voskhod programme. - Landing is the last part of a flight, where a flying animal, aircraft, or spacecraft returns to the ground. When the flying object returns to water, the process is called alighting, although it is commonly called "landing," "touchdown" or "splashdown" as well. A normal aircraft flight would include several parts of flight including taxi, takeoff, climb, cruise, descent and landing. - A space station, also known as an orbital station or an orbital space station, is a spacecraft capable of supporting crewmembers, which is designed to remain in space (most commonly as an artificial satellite in low Earth orbit) for an extended period of time and for other spacecraft to dock. A space station is distinguished from other spacecraft used for human spaceflight by lack of major propulsion or landing systems. Instead, other vehicles transport people and cargo to and from the station. three space stations are in orbit: the International Space Station, which is permanently manned, China's Tiangong-1 (defunct) and Tiangong-2 (launched 15 September 2016, not permanently manned). Previous stations include the Almaz and Salyut series, Skylab, and most recently "Mir". - Soyuz 21 ( Russian : 21 , Union 21 ) was a 1976 Soviet manned mission to the Salyut 5 space station , the first of three flights to the station . The mission 's objectives were mainly military in scope , but included other scientific work . The mission ended abruptly with cosmonauts Boris Volynov and Vitaly Zholobov returning to earth after 49 days in orbit . The precise reason for the early end of the mission was the subject of much speculation , but was reported to be an emergency evacuation after the Salyut atmosphere developed an acrid odor . - Skylab was the United States' first space station, orbiting Earth from 1973 to 1979, when it fell back to Earth amid huge worldwide media attention. Launched and operated by NASA, Skylab included a workshop, a solar observatory, and other systems necessary for crew survival and scientific experiments. It was launched unmanned by a modified Saturn V rocket, with a weight of . Lifting Skylab into low earth orbit was the final mission and launch of a Saturn V rocket (which was famous for carrying the manned Moon landing missions). Skylab was not simply a place of habitation; it was a place of massive science experiments for which when the bulk of data was returned, such as on films that had to be physically returned to Earth began the process of analyzing scientific and engineering data as each mission was completed. Skylab's solar observatory was one major aspect of study, and solar science was significantly advanced by the telescope; it observed the Sun as it never before. As Skylab finished up NASA's focus had shifted to development of the Space Shuttle, which had the promise of reducing the cost of space access compared to the previous launch systems What is the relationship between 'soyuz 21' and 'soyuz programme'?
The answer is:
part of