Soyuz 35 (, Union 35) was a 1980 Soviet crewed space flight to the Salyut 6 space station. It was the 10th mission to and eighth successful docking at the orbiting facility. The Soyuz 35 crew were the fourth long-duration crew to man the space station. Cosmonauts Leonid Popov and Valery Ryumin spent 185 days in space, setting a new space endurance record. Ryumin had completed a previous mission only eight months before. They hosted four visiting crews, including the first Hungarian, Cuban and Vietnamese cosmonauts. As long-duration crews now routinely swapped spacecraft with incoming crew, the Soyuz 35 craft was used to return the visiting Soyuz 36 crew to Earth, while the resident crew returned in Soyuz 37. Crew Backup crew Mission parameters Mass: Perigee: Apogee: Inclination: 51.65° Period: 88.81 minutes Crew launch, station activation Soyuz 35 was launched 9 April 1980 with Leonid Popov and Valery Ryumin aboard for a planned rendezvous with the orbiting Salyut 6 space station. The launch followed increased recent activity with the uncrewed space station. An uncrewed test craft, Soyuz T-1, spent several months docked to the station until it was undocked 23 March and deorbited 25 March. Progress 8, an uncrewed supply tanker, was launched almost immediately afterwards, on 27 March, and it docked with the rear dock port of the two-dock facility. Several manoeuvres were carried out by 2 April using the Progress to adjust the station's orbit. Valentin Lebedev had been scheduled to be Popov's flight engineer, but he was disqualified from launch after suffering a knee injury in a trampoline accident. As none of the back-up crew had previous flight experience (required since the failure of the Soyuz 25 mission), Ryumin had been given the choice of replacing Lebedev or delaying the mission. This despite having completed a six-month mission only the previous August. Ryumin's family was upset by this turn of events. The Soyuz 35 crew docked with and entered the space station on 10 April, using the vacant front port. Ryumin read the traditional note left by the previous crew, a note he had written with no expectation he would be the one receiving it. With Salyut 6 now entering its fourth year in orbit, some signs of wear and tear were becoming evident. Ryumin noted that the two viewports in the transfer compartment had lost their transparency. The windows also had many chips in them caused