DOS-5 flew as Salyut 6 in 1977. The dual docking ports allowed near-continuous occupation of the station through crew rotation. The opportunity presented by the need to replace the Soyuz ferry spacecraft at ninety-day intervals was taken to fly 'guest cosmonauts' from friendly countries on short visits to the stations. The Salyut 6 space station was the most successful of the DOS series prior to Mir. It was aloft for four years and ten months, completing 27,785 orbits of the earth. Five main expeditions and 11 short duration expeditions visited the station, of which nine had international crews. A total of 676 days of piloted operations were conducted by 27 cosmonauts with steadily increasing flight duration: 18, 75, 96, 140, and 185 days. 35 automatic dockings were conducted with the station by 20 Soyuz, 12 Progress, and 1 TKS spacecraft.

To support operation of these stations the basic Soyuz design was modified by addition of a docking tunnel. The resulting Soyuz 7KT-OK was used with the Salyut 1 DOS space station. Following the disastrous Soyuz 11 mission, it was again reworked to the simplified Soyuz 7K-T design, which finally provided a reliable ferry craft to Salyuts-4, and -6. A further modification was the Progress, an unmanned logistics vehicle that replaced the crew re-entry vehicle with propellant tanks for resupply of Salyut space stations. The Soyuz 7K-OK derivatives flew until succeeded by Soyuz T in 1981, which allowed a return to a three-man crew. The Soyuz T was derived from the still-born Soyuz 7K-S military version of Soyuz which began development in 1968.

• 1975 September 29 - Cosmos 772.  Spacecraft: Soyuz 7K-S. Mass: 6,750 kg (14,880 lb). Launch Site: Baikonur. Launch Vehicle: Soyuz 11A511U.

  Unmanned military Soyuz 7K-S test flight. Recovered October 3, 1975 4:10 GMT. Unsuccessful mission. Transmitted only on 166 MHz frequency, at none of the other usual Soyuz wavelengths.
  Maneuver Summary:
  193 km X 270 km orbit to 195 km X 300 km orbit. Delta V: 8 m/s
  196 km X 300 km orbit to 196 km X 328 km orbit. Delta V: 8 m/s
  Total Delta V: 16 m/s

• 1976 November 29 - Cosmos 869.  Spacecraft: Soyuz 7K-S. Mass: 6,800 kg (14,900 lb). Launch Site: Baikonur. Launch Vehicle: Soyuz 11A511U.

  Unmanned military Soyuz 7K-S test flight. Recovered December 17, 1976 10:31 GMT. Transmitted only on 20.008 MHz and 166 MHz frequencies, at none of the other usual Soyuz wavelengths.
  Maneuver Summary:
  196 km X 290 km orbit to 187 km X 335 km orbit. Delta V: 15 m/s
  187 km X 335 km orbit to 259 km X 335 km orbit. Delta V: 21 m/s
  259 km X 335 km orbit to 260 km X 345 km orbit. Delta V: 2 m/s
  260 km X 345 km orbit to 265 km X 368 km orbit. Delta V: 7 m/s
  265 km X 368 km orbit to 267 km X 391 km orbit. Delta V: 6 m/s
  267 km X 391 km orbit to 300 km X 310 km orbit. Delta V: 32 m/s
  Total Delta V: 83 m/s

• 1977 September 29 - Salyut 6.  Spacecraft: Salyut 6. Mass: 19,824 kg (43,704 lb). Launch Site: Baikonur. Launch Vehicle: Proton 8K82K.

  Conduct of scientific and technical research and experiments; further testing of station design, on-board system and equipment. Soyuz 25 docking unsuccessful. EVA 20 Dec 1977 to examine forward docking port (no damage). EVA 29 July 1978 to retrieve externally mounted experiments (micrometeorites, biopolymers, radiation plates, materials tests). Soyuz 33 failure to dock due to propulsion failure April 1979. Soyuz 34 launched unmanned to provide replacement vehicle June 1979. EVA August 15 to dislodge 10 m diameter KRT-10 radio telescope from aft docking collar. Repair mission Soyuz T-3 December 1980 (temperature control hydraulics). Repair mission Soyuz T-4 March 1981 (stuck solar array). Salyut ejected a module on May 31 (perhaps retained Soyuz Orbital Module). Kosmos 1267 docks 19 June 1981. Commanded to reentry using Kosmos 1267 propulsion system over Pacific July 29 1982.

  Maneuver Summary:
  214 km X 253 km orbit to 214 km X 260 km orbit. Delta V: 2...more.

• 1977 October 9 - Soyuz 25.  Spacecraft: Soyuz 7K-T. Mass: 6,860 kg (15,120 lb). Launch Site: Baikonur. Launch Vehicle: Soyuz 11A511U.

  Manned two crew. Unsuccessful mission. Failed to dock with Salyut 6.

• 1977 October 11 - Landing of Soyuz 25. 

  Soyuz 25 landed at 03:24 GMT.

• 1977 December 10 - Soyuz 26.  Spacecraft: Soyuz 7K-T. Mass: 6,800 kg (14,900 lb). Launch Site: Baikonur. Launch Vehicle: Soyuz 11A511U.

  Manned two crew. Docked with Salyut 6. Carried Yuri Romanenko, Georgi Grechko to Salyut 6; returned crew of Soyuz 27 to Earth. Conduct of joint experiments with the Salyut-6 scientific station.

• 1977 December 19 - EVA Salyut 6 EO-1-1.  Spacecraft: Salyut 6.

  Inspected Salyut 6 docking port.

• 1978 January 10 - Soyuz 27.  Spacecraft: Soyuz 7K-T. Mass: 6,800 kg (14,900 lb). Launch Site: Baikonur. Launch Vehicle: Soyuz 11A511U.

  Manned two crew. Carried Oleg Makarov, Vladimir Dzhanibekov to Salyut 6; returned crew of Soyuz 26 to Earth. Docked with Salyut 6.

• 1978 January 16 - Landing of Soyuz 26. 

  Soyuz 26 landed at 11:25 GMT with the crew of Dzhanibekov and Makarov aboard.

• 1978 January 20 - Progress 1.  Spacecraft: Progress. Mass: 7,020 kg (15,470 lb). Launch Site: Baikonur. Launch Vehicle: Soyuz 11A511U.

  Unmanned supply vessel to Salyut 6. Delivery of fuel, consumable materials and equipment to the Salyut 6 station. Docked with Salyut 6 on 22 Jan 1978 10:12:14 GMT. Undocked on 6 Feb 1978 05:54:00 GMT. Destroyed in reentry on 8 Feb 1978 02:00:00 GMT. Total free-flight time 3.91 days. Total docked time 14.82 days.

• 1978 March 2 - Soyuz 28.  Spacecraft: Soyuz 7K-T. Mass: 6,800 kg (14,900 lb). Launch Site: Baikonur. Launch Vehicle: Soyuz 11A511U.

  Manned two crew. Docked with Salyut 6. Delivery to the Salyut-6 station of the first international 'Intercosmos' team consisting of A.A. Gubarev (USSR) and V. Remek (Czechoslovak Socialist Republic) to carry out scientific research and experiments jointly developed by Soviet a nd Czechoslovak specialists.

• 1978 March 10 - Landing of Soyuz 28. 

  Soyuz 28 landed at 13:44 GMT.

• 1978 March 16 - Landing of Soyuz 27. 

  Soyuz 27 landed at 11:19 GMT with the crew of Grechko and Romanenko aboard.

• 1978 April 4 - Cosmos 1001.  Spacecraft: Soyuz T. Mass: 6,850 kg (15,100 lb). Launch Site: Baikonur. Launch Vehicle: Soyuz 11A511U.

  Manned precursor. Recovered April 15, 1978 12:02 GMT. Unsuccessful mission. Soyuz T test -failure.
  Maneuver Summary:
  202 km X 231 km orbit to 195 km X 291 km orbit. Delta V: 19 m/s
  195 km X 291 km orbit to 306 km X 322 km orbit. Delta V: 40 m/s
  306 km X 322 km orbit to 308 km X 318 km orbit. Delta V: 1 m/s
  Total Delta V: 60 m/s.
  Officially: Investigation of the upper atmosphere and outer space.

• 1978 June 15 - Soyuz 29.  Spacecraft: Soyuz 7K-T. Mass: 6,800 kg (14,900 lb). Launch Site: Baikonur. Launch Vehicle: Soyuz 11A511U.

  Manned two crew. Docked with Salyut 6. Placed on board the Salyut-6 station a crew consisting of V.V. Kovalenko and A.S. Ivanchenkov to conduct scientific and technological investigations and experiments.

• 1978 June 27 - Soyuz 30.  Spacecraft: Soyuz 7K-T/A9. Mass: 6,800 kg (14,900 lb). Launch Site: Baikonur. Launch Vehicle: Soyuz 11A511U.

  Manned two crew. Docked with Salyut 6. Placed on board the Salyut-6 station, under the Intercosmos programme, a second, international, crew consisting of P.I. Klimuk (USSR) and M. Hermaszewski (Poland) to conduct scientific investigations and experiments.

• 1978 July 5 - Landing of Soyuz 30. 

  Soyuz 30 landed at 13:29 GMT.

• 1978 July 7 - Progress 2.  Spacecraft: Progress. Mass: 7,014 kg (15,463 lb). Launch Site: Baikonur. Launch Vehicle: Soyuz 11A511U.

  Unmanned supply vessel to Salyut 6. Delivery of fuel, consumable materials and equipment to the Salyut 6 station. Docked with Salyut 6 on 9 Jul 1978 12:58:59 GMT. Undocked on 2 Aug 1978 04:57:44 GMT. Destroyed in reentry on 4 Aug 1978 01:31:07 GMT. Total free-flight time 3.92 days. Total docked time 23.67 days.

• 1978 July 29 - EVA Salyut 6 EO-2-1.  Spacecraft: Salyut 6.

  Retrieved material samples and equipment.

• 1978 August 7 - Progress 3.  Spacecraft: Progress. Mass: 7,014 kg (15,463 lb). Launch Site: Baikonur. Launch Vehicle: Soyuz 11A511U.

  Unmanned supply vessel to Salyut 6. Delivery of fuel, consumable materials and equipment to the Salyut 6 station. Docked with Salyut 6 on 9 Aug 1978 23:59:30 GMT. Undocked on 21 Aug 1978 15:42:50 GMT. Destroyed in reentry on 23 Aug 1978 16:45:00 GMT. Total free-flight time 4.10 days. Total docked time 11.66 days.

• 1978 August 20 - Kamanin in Star City.. 

  At a visit to Star City, Kamanin is allowed to participate together with Yeliseyev in a communications session with the EO-2 crew (Ivanchenkov, Kovalyonok) aboard Salyut 6.

• 1978 August 26 - Soyuz 31.  Spacecraft: Soyuz 7K-T. Mass: 6,800 kg (14,900 lb). Launch Site: Baikonur. Launch Vehicle: Soyuz 11A511U.

  Manned two crew. Docked with Salyut 6. Delivered to the Salyut-6 station the third international 'Intercosmos' crew consisting of V F Bykovsky (USSR) and S Jaehn (German Democratic Republic) to carry out scientific research and experiments.

• 1978 September 3 - Landing of Soyuz 29. 

  Soyuz 29 landed at 11:40 GMT with the crew of Bykovsky and Jaehn aboard.

• 1978 October 3 - Progress 4.  Spacecraft: Progress. Mass: 7,014 kg (15,463 lb). Launch Site: Baikonur. Launch Vehicle: Soyuz 11A511U.

  Unmanned supply vessel to Salyut 6. Delivery of fuel, consumable materials and equipment to the Salyut 6 station. Docked with Salyut 6 on 6 Oct 1978 01:00:15 GMT. Undocked on 24 Oct 1978 13:01:52 GMT. Destroyed in reentry on 26 Oct 1978 16:28:13 GMT. Total free-flight time 4.22 days. Total docked time 18.50 days.

• 1978 November 2 - Landing of Soyuz 31. 

  Soyuz 31 landed at 11:05 GMT with the crew of Ivanchenkov and Kovalyonok aboard.

• 1979 January 31 - Cosmos 1074.  Spacecraft: Soyuz T. Mass: 6,850 kg (15,100 lb). Launch Site: Baikonur. Launch Vehicle: Soyuz 11A511U.

  Manned precursor. Recovered April 1, 1979 10:09 GMT. Soyuz T Test.
  Maneuver Summary:
  197 km X 240 km orbit to 255 km X 297 km orbit. Delta V: 33 m/s
  255 km X 297 km orbit to 264 km X 306 km orbit. Delta V: 4 m/s
  264 km X 306 km orbit to 309 km X 321 km orbit. Delta V: 17 m/s
  309 km X 321 km orbit to 279 km X 357 km orbit. Delta V: 18 m/s
  279 km X 357 km orbit to 352 km X 402 km orbit. Delta V: 32 m/s
  352 km X 402 km orbit to 363 km X 384 km orbit. Delta V: 8 m/s
  Total Delta V: 112 m/s
  Officially: Investigation of the upper atmosphere and outer space.

• 1979 February 25 - Soyuz 32.  Spacecraft: Soyuz 7K-T. Mass: 6,800 kg (14,900 lb). Launch Site: Baikonur. Launch Vehicle: Soyuz 11A511U.

  Manned two crew. Docked with Salyut 6. Transported a team consisting of V A Lyakhov and V V Ryumin to the Salyut-6 space station to conduct scientific investigations and experiments and repair work. Recovered June 15, 1979 16:18 GMT. Returned unmanned.

• 1979 March 12 - Progress 5.  Spacecraft: Progress. Mass: 7,014 kg (15,463 lb). Launch Site: Baikonur. Launch Vehicle: Soyuz 11A511U.

  Unmanned supply vessel to Salyut 6. Delivery of fuel, consumable materials and equipment to the Salyut 6 station. Docked with Salyut 6 on 14 Mar 1979 07:19:21 GMT. Undocked on 3 Apr 1979 16:10:00 GMT. Destroyed in reentry on 5 Apr 1979 00:10:22 GMT. Total free-flight time 3.40 days. Total docked time 20.37 days.

• 1979 April 10 - Soyuz 33.  Spacecraft: Soyuz 7K-T. Mass: 6,860 kg (15,120 lb). Launch Site: Baikonur. Launch Vehicle: Soyuz 11A511U.

  Manned two crew. Flight under the Intercosmos programme of an international team consisting of N N Rukavishnikov (USSR) and G I Ivanov (Bulgaria). Unsuccessful mission. Failed to rendezvous with Salyut 6.

• 1979 April 12 - Landing of Soyuz 33. 

  Soyuz 33 landed at 16:35 GMT.

• 1979 May 13 - Progress 6.  Spacecraft: Progress. Mass: 7,014 kg (15,463 lb). Launch Site: Baikonur. Launch Vehicle: Soyuz 11A511U.

  Unmanned supply vessel to Salyut 6. Delivery of fuel, consumable materials and equipment to the Salyut 6 station. Docked with Salyut 6 on 15 May 1979 06:19:22 GMT. Undocked on 8 Jun 1979 07:59:41 GMT. Destroyed in reentry on 9 Jun 1979 18:52:46 GMT. Total free-flight time 3.54 days. Total docked time 24.07 days.

• 1979 June 6 - Soyuz 34.  Spacecraft: Soyuz 7K-T. Mass: 6,800 kg (14,900 lb). Launch Site: Baikonur. Launch Vehicle: Soyuz 11A511U.

  Docked with Salyut 6. Launched unmanned to provide return vehicle for Soyuz 32 crew of Lyakhov/Ryumin after Soyuz 33 primary propulsion system failure. Checked the operation of the spacecraft propulsion unit; transportated the crew of the Salyut-6 station back to earth.

• 1979 June 15 - Landing of Soyuz 32. 

  Soyuz 32 landed at 16:18 GMT.

• 1979 June 28 - KRT-10.  Launch Site: Baikonur. Launch Vehicle: Soyuz 11A511U.

  10 m diameter radio telescope. Attached to Salyut 6 docking hatch and deployed after separation of Progress from Mir.

• 1979 June 28 - Progress 7.  Spacecraft: Progress. Mass: 7,014 kg (15,463 lb). Launch Site: Baikonur. Launch Vehicle: Soyuz 11A511U.

  Unmanned supply vessel to Salyut 6. Delivery of fuel, consumable materials and equipment to the Salyut 6 station. Docked with Salyut 6 on 30 Jun 1979 11:18:22 GMT. Undocked on 18 Jul 1979 03:49:55 GMT. Destroyed in reentry on 20 Jul 1979 01:57:30 GMT. Total free-flight time 4.0 days. Total docked time 17.69 days.

• 1979 August 15 - EVA Salyut 6 EO-3-1.  Spacecraft: Salyut 6.

  Jettisoned KRT-10 antenna from rear docking port.

• 1979 August 19 - Landing of Soyuz 34. 

  Soyuz 34 landed at 12:30 GMT with the crew of Lyakhov and Ryumin aboard.

• 1979 December 16 - Soyuz T-1.  Spacecraft: Soyuz T. Mass: 6,850 kg (15,100 lb). Launch Site: Baikonur. Launch Vehicle: Soyuz 11A511U.

  New generation Soyuz capsule; unmanned flight to Salyut 6. Docked with Salyut 6. Recovered March 25, 1980 21:47 GMT. Unmanned test of Soyuz T design.
  Officially: Complex experimental testing of new on-board systems and assemblies under various flight conditions and operation in conjunction with the Salyut-6 orbital station.

• 1980 March 27 - Progress 8.  Spacecraft: Progress. Mass: 7,014 kg (15,463 lb). Launch Site: Baikonur. Launch Vehicle: Soyuz 11A511U.

  Unmanned supply vessel for Salyut 6. Delivery of various cargoes to the Salyut-6 orbital station. Docked with Salyut 6 on 29 Mar 1980 20:01:00 GMT. Undocked on 25 Apr 1980 08:04:00 GMT. Destroyed in reentry on 26 Apr 1980 06:54:00 GMT. Total free-flight time 3.0 days. Total docked time 26.50 days.

• 1980 April 9 - Soyuz 35.  Spacecraft: Soyuz 7K-T. Mass: 6,800 kg (14,900 lb). Launch Site: Baikonur. Launch Vehicle: Soyuz 11A511U.

  Manned two crew. Docked with Salyut 6. Carried crew comprising L I Popov and V V Ryumin to the Salyut-6 station to carry out scientific and technical research and experiments.

• 1980 April 27 - Progress 9.  Spacecraft: Progress. Mass: 7,014 kg (15,463 lb). Launch Site: Baikonur. Launch Vehicle: Soyuz 11A511U.

  Unmanned supply vessel for Salyut 6. Delivery of various cargoes to the Salyut-6 orbital station. Docked with Salyut 6 on 29 Apr 1980 08:09:19 GMT. Undocked on 20 May 1980 18:51:00 GMT. Destroyed in reentry on 22 May 1980 00:44:00 GMT. Total free-flight time 3.32 days. Total docked time 21.45 days.

• 1980 May 26 - Soyuz 36.  Spacecraft: Soyuz 7K-T. Mass: 6,800 kg (14,900 lb). Launch Site: Baikonur. Launch Vehicle: Soyuz 11A511U.

  Transported the fifth international crew under the INTERCOSMOS programme, comprising V N Kubasov (USSR) and B Farkas (Hungary) to the Salyut-6 station to carry out scientific research and experiments.

• 1980 June 3 - Landing of Soyuz 35. 

  Soyuz 35 landed at 15:07 GMT, 140 km SE Dzehezkazgan, with the crew of Farkas and Kubasov aboard.

• 1980 June 5 - Soyuz T-2.  Spacecraft: Soyuz T. Mass: 6,850 kg (15,100 lb). Launch Site: Baikonur. Launch Vehicle: Soyuz 11A511U.

  Test flight of new Soyuz T; docked with Salyut 6. Conducted testing and development of on-board systems in the improved Soyuz T series transport vehicle under piloted conditions.

• 1980 June 9 - Landing of Soyuz T-2. 

  Soyuz T-2 landed at 12:38 GMT.

• 1980 June 29 - Progress 10.  Spacecraft: Progress. Mass: 7,014 kg (15,463 lb). Launch Site: Baikonur. Launch Vehicle: Soyuz 11A511U.

  Unmanned supply vessel for Salyut 6. Delivery of various cargoes to the Salyut-6 orbital station. Docked with Salyut 6 on 1 Jul 1980 05:53:00 GMT. Undocked on 17 Jul 1980 22:21:00 GMT. Destroyed in reentry on 19 Jul 1980 01:47:00 GMT. Total free-flight time 3.19 days. Total docked time 16.69 days.

• 1980 July 23 - Soyuz 37.  Spacecraft: Soyuz 7K-T. Mass: 6,800 kg (14,900 lb). Launch Site: Baikonur. Launch Vehicle: Soyuz 11A511U.

  Manned two crew. Transported to the Salyut-6 station the sixth international crew under the Intercosmos programme, comprising V V Gorbatko (USSR) and Pham Tuan (Viet Nam), to conduct scientific research and experiments. Returned crew of Soyuz 35 to Earth. Recovered October 11, 1980 9:50 GMT.

• 1980 July 31 - Landing of Soyuz 36. 

  Soyuz 36 landed at 15:15 GMT with the crew of Gorbatko and Tuan aboard.

• 1980 September 18 - Soyuz 38.  Spacecraft: Soyuz 7K-T. Mass: 6,800 kg (14,900 lb). Launch Site: Baikonur. Launch Vehicle: Soyuz 11A511U.

  Manned two crew. Docked with Salyut 6. Transported to the Salyut-6 station the seventh international crew under the INTERCOSMOS programme, comprising Y V Romanenko (USSR) and A. Tomaio Mendez (Cuba), to conduct scientific research and experiments.

• 1980 September 26 - Landing of Soyuz 38. 

  Soyuz 38 landed at 15:54 GMT.

• 1980 September 28 - Progress 11.  Spacecraft: Progress. Mass: 7,014 kg (15,463 lb). Launch Site: Baikonur. Launch Vehicle: Soyuz 11A511U.

  Unmanned supply vessel for Salyut 6. Delivery of various cargoes to the Salyut-6 orbital station. Docked with Salyut 6 on 30 Sep 1980 17:03:00 GMT. Undocked on 9 Dec 1980 10:23:00 GMT. Destroyed in reentry on 11 Dec 1980 14:00:00 GMT. Total free-flight time 4.23 days. Total docked time 69.72 days.

• 1980 October 11 - Landing of Soyuz 37. 

  Soyuz 37 landed at 09:50 GMT with the crew of Popov and Ryumin aboard.

• 1980 November - Soyuz T-3A (cancelled).  Spacecraft: Soyuz T.

  Planned but cancelled manned flight. Crew dissolved when Lazarev failed physical in early 1981.

• 1980 November 27 - Soyuz T-3.  Spacecraft: Soyuz T. Mass: 6,850 kg (15,100 lb). Launch Site: Baikonur. Launch Vehicle: Soyuz 11A511U.

  Manned three crew. Docked with Salyut 6. Tested the improved transport ship of the 'SOYUZ T' series; transported to the Salyut-6 orbital station a crew consisting of L D Kizim, O G Makarov and G M Strekalov to carry out repair and preventive work and scientific and technical investigation and experiments.

• 1980 December 10 - Landing of Soyuz T-3. 

  Soyuz T-3 landed at 09:25 GMT.

• 1981 January 24 - Progress 12.  Spacecraft: Progress. Mass: 7,020 kg (15,470 lb). Launch Site: Baikonur. Launch Vehicle: Soyuz 11A511U.

  Unmanned supply vessel to Salyut 6. Delivery of various cargoes to the Salyut-6 orbital station. Docked with Salyut 6 on 26 Jan 1981 15:56:00 GMT. Undocked on 19 Mar 1981 18:14:00 GMT. Destroyed in reentry on 20 Mar 1981 16:59:00 GMT. Total free-flight time 3.02 days. Total docked time 52.10 days.

• 1981 March 12 - Soyuz T-4.  Spacecraft: Soyuz T. Mass: 6,850 kg (15,100 lb). Launch Site: Baikonur. Launch Vehicle: Soyuz 11A511U.

  Manned two crew. Docked with Salyut 6. Transported to the Salyut-6 orbital station cosmonauts V V Kovalenok and V P Savinykh to carry out repairs and preventive maintenance and scientific and technical investigations and experiments.

• 1981 March 22 - Soyuz 39.  Spacecraft: Soyuz 7K-T. Mass: 6,800 kg (14,900 lb). Launch Site: Baikonur. Launch Vehicle: Soyuz 11A511U.

  Manned two crew. Docked with Salyut 6. Transported to the Salyut-6 orbital station the eighth international crew under the INTERCOSMOS programme, comprising V A Dzhanibekov (USSR) and Z. Gurragchi (Mongolian People's Republic) to conduct scientific investigations and experiments.

• 1981 March 30 - Landing of Soyuz 39. 

  Soyuz 39 landed at 11:41 GMT.

• 1981 May 14 - Soyuz 40.  Spacecraft: Soyuz 7K-T. Mass: 6,800 kg (14,900 lb). Launch Site: Baikonur. Launch Vehicle: Soyuz 11A511U.

  Manned two crew. Docked with Salyut 6. Transported to the Salyut-6 orbital station the ninth international crew under the INTERCOSMOS programme, comprising L I Popov (USSR), and D. Prunariu (Romania), to conduct scientific research and experiments.

• 1981 May 22 - Landing of Soyuz 40. 

  Soyuz 40 landed at 13:58 GMT.

• 1981 May 26 - Landing of Soyuz T-4. 

  Soyuz T-4 landed at 12:37 GMT.