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|Mission name||Soyuz T-15|
|Call sign||Mayak (Beacon)|
|Launch date||13 March 1986
|Landing||16 July 1986
55 km NE of Arkalyk
|Mission duration||125 days, 56 seconds|
|Number of orbits||1980|
The Soyuz-T (Russian: Союз-T, Union-T) spacecraft was the third generation Soyuz spacecraft, in service for seven years from 1979 to 1986. The T stood for transport (транспортный, Transportny). The revised spacecraft incorporated lessons learned from the Apollo Soyuz Test Project, Soyuz 7K-TM and Military Soyuz.
The Soyuz-T was a major upgrade over previous Soyuz spacecraft, sporting solid-state electronics for the first time and a much more advanced onboard computer to help overcome the chronic docking problems that affected cosmonauts during space station missions. In addition, solar panels returned, allowing the Soyuz-T to fly up to 11 days independently as well as a redesigned propulsion system. Finally, it could at last carry three cosmonauts with pressure suits.
|Country of origin||Soviet Union|
|Applications||Carry three cosmonauts to Salyut and Mir space stations and back|
|Orbit regimes||Low Earth orbit|
|Operator||Soviet space program|
|Derived from||Soyuz 7K-TM
|Status||Out of service|
|First launch||Soyuz T-1, 1979|
|Last launch||Soyuz T-15, 1986|
|Flight Engineer||Vladimir Solovyov
Backup crew 
|Flight Engineer||Aleksandr Aleksandrov|
Mission parameters 
- Mass: 6850 kg
- Perigee: 331 km
- Apogee: 366 km
- Inclination: 51.6°
- Period: 91.5 minutes
Mission highlights 
Soyuz T-15 was the first expedition to Mir.
Flight to Mir 
Due to the pressure of launching Mir in time for the 27th Communist Party Congress, mission planners were left without the newer Soyuz-TM spacecraft or any of the planned modules to launch to the station at first. It was decided to launch an older Soyuz T as Soyuz T-15 on a dual mission to both Mir and Salyut 7.
Leonid Kizim and Vladimir Solovyov first docked with the Mir space station on 15 March 1986 after their launch on 13 March. Plans for Mir intended that only the newer Soyuz-TM would dock with Mir's forward port, leaving the aft port free for arriving Progress spacecraft. However, the older Soyuz-T actually used for the first Soyuz T-15 mission to Mir was not equipped with the Kurs approach system used on Mir's front port, but only with the older Igla approach system used for Mir's aft port. Therefore Soyuz T-15 had to approach Mir's aft port, and then manually maneuver around the station to dock manually at the forward port. At 20 km Soyuz T-15's Igla system acquired its counterpart on Mir's aft port. At 200 meters, the Igla system was shut off, and the crew manually maneuvered around the station to dock at the front port. For this manual approach, the same laser range finder was used as for the Soyuz T-13 docking with the uncooperative Salyut 7 station in 1985.
The crew transfers to Salyut 7 
In preparation for the trip to Salyut 7, the crew loaded Soyuz T-15 with their personal belongings, plants grown on Mir, and other items. At that time Salyut 7 was still 4000 km ahead of Mir in a lower orbit. Therefore on 4 May Mir was lowered by 13 km in order to speed the approach to Salyut 7 and conserve Soyuz T-15's limited fuel supply for the transfer. On 5 May 1986 12:12:09 UTC they undocked from Mir for their journey to Salyut 7 – at this time, the distance between the two space stations has shrunken to 2500 km due to Mir's maneuver. After a crossing of 29 hours, Soyuz T-15 docked with Salyut 7 on 6 May 16:57:52 UTC.
Experiments on Salyut 7 
The previous crew on Salyut 7, Salyut 7 EO-4, had been assigned to conduct experiments with TKS-4 (Kosmos 1686). However, commander Vladimir Vasyutin had fallen ill and the crew had to return prematurely to Earth. Therefore they were unable to perform EVAs, which would have had implications for the Mir program. After arriving at Salyut 7, the crew of Soyuz T-15 therefore conducted two EVAs and collected experiment results, experimental apparatus, and samples of materials to finish the work of the previous crew.
The first EVA was on 28 May, when the crewmembers climbed outside to retrieve space exposure experiments and test the Ferma-Postroital ("girder-constructor") device. A deployment canister converted a folded girder cartridge into a 15-meter girder in only a few minutes. The girder was retracted by reversing the process at the end of the EVA. This first EVA lasted 3 hours and 50 minutes. The second EVA consisted of girder and welding experiments. On 31 May, Kizim and Solovyov attached measurement devices to the top of the retracted girder, then re-extended it with an aim toward studying its rigidity. They then used an electron gun to weld several of the girder's joints. This second EVA lasted five hours.
Ferry flight back to Mir 
The crew removed 20 instruments with a total mass of 350 to 400 kg from Salyut 7 before returning to Mir. Mir maneuvered twice again 24–25 June, raising its orbit slightly and moving closer to Salyut 7. On 25 June, Soyuz T-15 undocked from Salyut 7 to begin their 29 hour journey back to Mir, to which they returned on 25–26 June.
On 3 July, Kizim surpassed Valeri Ryumin's record for time spent in space. On 6 July, he became the first human to have spent a full year in space. The crew spent their last 20 days on Mir conducting Earth observations.
Meanwhile between 19 and 22 August, engines on Cosmos 1686 boosted Salyut 7 to a record-high mean orbital altitude of 475 km to forestall reentry. Atmospheric drag took its toll, however, and the station reentered over South America 55 months later. Pieces of Salyut 7 and Cosmos 1686 were found in Argentina.
See also 
- Soyuz 10, the first mission to dock to a space station, which had to be aborted as hard-dock with Salyut 1 was not able to be accomplished.
- Soyuz T-13, a mission to manually dock to the crippled Salyut 7 space station.
Other Soyuz T Missions 
- Soyuz T-1 (unmanned test, launched 1979)
- Soyuz T-2
- Soyuz T-3
- Soyuz T-5
- Soyuz T-6
- Soyuz T-7
- Soyuz T-8
- Soyuz T-9
- Soyuz T-10-1
- Soyuz T-10
- Soyuz T-11
- Soyuz T-12
- Soyuz T-13
- Soyuz T-14
- Soyuz T-15 (launched 1986)