The Soviet Union launches the Soyuz 10 mission, intended to become the first crew to occupy an Earth-orbiting space station. Flying a new modification of the Soyuz vehicle, fitted with a new system for docking to the Salyut 1 space station, are Vladimir Shatalov, Alexei Yeliseyev and Nikolai Rukavishnikov, but they won’t be the first space station crew in history: the Soyuz capsule fails to hard-dock to the station, making it impossible for them to enter. Soyuz 10 returns to Earth after two days, and even on the return journey the cosmonauts are sickened by toxic fumes in their environmental system. Salyut 1 remains in orbit, still unmanned.
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The 20th episode of Gerry Anderson’s live-action UFO series airs on ITV, starring Edward Bishop and Michael Billington. George Sewell and Grant Taylor guest star.
The 
NASA and JPL launch Mariner 8, the first of two identical “Mars ’71” orbiters designed to visit Mars. Where previous missions have simply flown past the red planet, Mariners 8 and 9 are intended to put themselves in orbit and remain there to map the majority of the Martian surface. The second stage of the Atlas-Centaur booster used to launch Mariner 8 fails, however, and the robotic Mars explorer crashes into the Atlantic Ocean. Some of its mission objectives are transferred to the identical Mariner 9, due for launch at the end of the month.
The 
BBC2 airs the 43rd episode of science fiction anthology series Out Of The Unknown. Written by Edward Boyd, the story stars Malcolm Tierney and Pamela Salem. This episode no longer exists in the BBC’s archives.
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The third Planet Of The Apes film, 
After a tuberculosis scare forces Soviet space officials to ground the mission’s original crew, the backup crew of Soyuz 11 lifts off to become the first occupants of a manned space station. Experiencing none of the difficulties that plagued the earlier Soyuz 10 attempt to dock with Salyut 1, the Soyuz 11 crew stays aboard Salyut for 22 days, a new record for a manned space mission.
The National Severe Storms Laboratory‘s 10cm Doppler weather radar begins full-time experimental operation in Norman, Oklahoma, just in time for the region’s active severe weather season. A surplus Air Force radar left over from the Distant Early Warning radar network (also known as the DEW Line) is installed and housed in a facility that’s also made of military surplus parts. There is no real-time display at first: researchers and meteorologists store the Doppler radar’s observations on computer tape that has to be processed and printed months after the fact, and compared to archived records from the existing WSR-57 radar at Norman.
Though the race to the moon has already been lost, the Soviet space program continues to refine its giant N1 rocket, conducting extensive modifications to nearly all of its systems. The third N1 to lift off almost immediately loses directional control, forcing ground controllers to signal it to self-destruct less than a mile off the ground. Its cargo is an unmanned Soyuz/Korabl combo – the Soviet answer to the Apollo command/service module and landing module – though this time there is no launch escape system, so the vehicle is destroyed along with its booster.
London Weekend Television premieres the first episode of the alternate-future-history series The Guardians, starring Gwyneth Powell and Cyril Luckham. The series deals with a near-future Britain under the heel of a fascist regime, and a resistance movement attempting to undermine that government.
ITV airs 
Threshold Records releases