Apollo-Soyuz Test Project (ASTP) July 15, 1975 – July 24, 1975


Apollo LogoTHE FLIGHT OFSoyuz Logo


Flight Crew:

  • Apollo
    • Thomas P. Stafford
    • Vance D. Brand
    • Donald K. Slayton
  • Soyuz
    • Alexey A. Leonov
    • Valery N. Kubasov


  • Apollo: July 15, 1975
  • Soyuz: July 15, 1975


  • Apollo: July 24, 1975
  • Soyuz: July 21, 1975

Mission Duration:

  • 09 days, 07 hours, 28 minutes
  • July 15-24, 1975

Mission Highlights:

The Soyuz was launched just over seven hours prior to the launch of the Apollo CSM. Apollo then maneuvered to rendezvous and docking 52 hours after the Soyuz launch. The Apollo and Soyuz crews conducted a variety of experiments over a two-day period. After separation, Apollo remained in space an additional 06 days. Soyuz returned to Earth approximately 30 hours after separation.

Mission Narrative:

The final flight of the Apollo program was the first spaceflight in which spacecraft from different nations docked in space. In July 1975, a U.S. Apollo spacecraft carrying a crew of three docked with a Russian Soyuz spacecraft with its crew of two.

For the Apollo-Soyuz Test Project (ASTP), the United States used an Apollo Command and Service Module (CSM) modified to provide for experiments to be conducted during the mission, extra propellant tanks and the addition of controls and equipment related to the Docking Module. Launch was accomplished with a Saturn IB.

The Docking Module was designed jointly by the United States and Soviet Union, and built in the United States. Its purpose was to enable a docking between the dissimilar Soyuz spacecraft and the U.S. Apollo. It was a three meter long cylinder 1.5 meters in diameter, and in addition to serving as a docking device, also served as an airlock module between the different atmospheres of the two ships (the U.S. ship with 100% oxygen at 260 millimeters of mercury; the Soyuz with a mixed oxygen-nitrogen atmosphere at 520 mm HG–lowered from its usual 760 mm Hg for this mission).

Prior to the conduct of ASTP, the astronauts and cosmonauts visited each other’s space centers and became familiar with the spacecraft of the other country. The first visit was by the Russians to Johnson Space Center in July 1973, followed by a U.S. visit to Moscow in November 1973. In late April and early May 1974, the Russian flight crews returned to Johnson Space Center, and the U.S. crews went to Moscow in June and July 1974. The Russian crew made a third trip to the United States in September 1973 and came for the fourth and last time in February 1975. The U.S. crew visited the Soviet Union in late April and early May 1975 and became the first Americans to see the Russian launch facilities at Tyuratam on April 28, 1975.

Three simulation sessions were conducted between flight controllers and the ASTP crew in Houston and Moscow on May 13, 15 and 18, 1975 involving communications links between the two control centers, and fully occupied control center facilities. A final simulation was conducted from June 30-July 1, 1975. Additionally, in December 1974, the Russians made a human flight of the modified version of the Soyuz spaceship for system tests (Soyuz 16).

One of the most difficult problems to overcome was that of language differences. To alleviate this problem as much as possible, the Americans learned Russian and the Russians learned English. It was found that the best scenario was for the Russians to speak English and for the Americans to speak Russian.

Soyuz Launch: Soyuz 19, carrying cosmonauts Aleksey A. Leonov and Valery N. Kubasov, was launched into sunny skies from Baykonur Cosmodrome at 5:20 pm local time (8:20 am EDT) July 15, 1975. The spacecraft entered orbit with a 221.9-km apogee, 186.3-km perigee, 88.5-min period, and 51.8 inclination.

Foreign correspondents, barred from the launch site, watched the launch on color TV sets in a Moscow press center. The first Soviet launch to be televised live, it was transmitted to viewers throughout the Soviet Union, the U.S., and eastern and western Europe. President Ford watched from a U.S. State Dept. auditorium with Soviet Ambassador to the U.S, Anatoly P. Dobrynin and NASA Administrator James C. Fletcher, before Dr. Fletcher and Ambassador Dobrynin flew to Kennedy Space Center to watch the Apollo launch.

On the third orbit the Soyuz 19 crew established contact with U.S. mission control in Houston, putting into operation the global Moscow and Houston Soyuz-Apollo communications system. On the fifth orbit the cosmonauts made the first of two maneuvers to place Soyuz 19 into a circular docking orbit. New orbital parameters were 231.7-km apogee and 192.4-km perigee. The spacecraft was spin-stabilized at 3 per sec with all systems operating normally.

Apollo Launch: At 3:50 pm EDT July 15, 1975, 7 hr, 30 min, after the Soyuz launch-a Saturn IB flawlessly lifted the Apollo spacecraft from Kennedy Space Center’s launch complex 39, carrying Apollo commander Thomas P. Stafford, command-module pilot Vance D. Brand, and docking-module pilot Donald K. Slayton. The spacecraft entered orbit with a 173.3-km apogee, 154.7-km perigee, 87.6-min period, and 51.8 inclination. The spacecraft’s launch-vehicle adapter was jettisoned at 9 hr 4 min ground elapsed time (9:04 GET, counted from the Soyuz 19 launch) and the crew maneuvered the Apollo 180 to dock with the adapter and extract the docking module. These events were videotaped and transmitted to earth later via ATS 6 (NASA’s Applications Technology Satellite launched 30 May 1974). A maneuver 2 hr later at 7:35 pm circularized the orbit at 172 km. The Saturn S-IVB stage was deorbited into the Pacific Ocean 1 hr 30 min later.

A second Soyuz 19 circularization burn of 18.5 sec at 8:43 am EDT July 16 placed that spacecraft in a circular orbit of 229 km, with all systems functioning normally.

Rendezvous and Docking: A series of Apollo maneuvers, with the final braking maneuver at 8:51 am EDT July 17, put the Apollo spacecraft in a 229.4-km circular orbit matching the orbit of Soyuz 19. A few minutes later Brand reported, “We’ve got Soyuz in the sextant.” Voice contact was made soon after. Hello. Soyuz, Apollo,” Stafford said in Russian. Kubasov replied in English, “Hello everybody. Hi to you, Tom and Deke. Hello there, Vance.”

All communications among the five crew members during the mission were made in the language of the listener, with the Americans speaking Russian to the Soviet crew and the Soviet crew speaking English to the Americans. Contact of the two spacecraft, 51 hr, 49 min, into the mission (12:09 pm July 17) was transmitted live on TV to the earth, and Stafford commented, “We have succeeded. Everything is excellent.” “Soyuz and Apollo are shaking hands now,” the cosmonauts answered. Hard docking was completed over the Atlantic Ocean at 12:12 pm, 6 min earlier than the prelaunch flight plan watched by millions of TV viewers worldwide. “Perfect. Beautiful. Well done, Tom. It was a good show. We’re looking forward to shaking hands with you in board [sic] Soyuz,” Leonov said. Tass later reported that Kubasov told Moscow ground controllers that “we felt a slight jolt at the moment of docking” but that all went according to plan.

Joint Activities: At 3:17 pm hatch 3 opened; Apollo commander Stafford and Soyuz commander Leonov shook hands 2 min later. “Glad to see you,” Stafford told Leonov in Russian. “Glad to see you. Very, very happy to see you,” Leonov responded in English. “This is Soyuz and the United States,” Slayton told TV viewers around the world. Both Soviet Communist Party General Secretary Leonid I. Brezhnev and President Ford congratulated the crews and expressed their confidence in the success of the mission. Stafford then presented Leonov with “five flags for your government and the people of the Soviet Union” with the wish that “our joint work in space serves for the benefit of all countries and peoples on the earth.” Leonov presented the U.S. crew with Soviet flags and plaques. The men signed international certificates and exchanged other commemorative items. After nearly 4 hrs of joint activities, including a meal aboard the Soyuz, the Americans returned to the Apollo and the hatch was closed at 6:51 pm.

An integrity check of the hatches indicated an atmospheric leak on the Soviet side. Ground controllers later attributed the indication to temperature changes in the sealed docking module that were detected by the sensitive Soviet instrumentation. Future integrity checks of the hatches would be more rigorous, however.

Following a sleep period, the crews prepared for another day of joint activity. Kubasov described the mission to Soviet TV viewers while the rest of the crews performed experiments in their respective spacecraft. At 5:05 am July 18, 1975, Brand entered the Soviet spacecraft; Leonov joined Stafford and Slayton in Apollo, greeting them with “Howdy partner.” Kubasov gave American TV viewers a tour of his Soyuz, and Stafford followed with a tour of the Apollo. Then both Kubasov and Brand videotaped scientific demonstrations for transmission to earth later. Kubasov and Brand ate lunch in the Soyuz while Leonov ate with Stafford and Slayton in Apollo.

During a third transfer, Stafford and Leonov went into the Soyuz and Kubasov and Brand joined Slayton in Apollo. Brand gave Soviet viewers a Russian-language tour of the eastern U.S. as seen from space. Further speeches and exchanges of commemorative items were made for both U.S. and Soviet viewers before the final handshakes at 4:49 pm EDT July 18, when the crews returned to their respective spacecraft. The hatches were closed after Brand told Leonov and Kubasov, “We wish you the host of success. I’m sure that we’ve opened up a new era in history. Our next meeting will be on the ground.” Total time for all transfers and joint activities was 19 hr 55 min. Stafford had spent 7 hr 10 min aboard Soyuz; Brand, 6 hr 30 min; Slayton, 1 hr 35 min. Leonov spent 5 hr 43 min in the Apollo, Kubasov 4 hr 57 min. During nearly 2 days of joint activities, the five men carried out five joint experiments.

Undocking and Separation: The Apollo and Soyuz spacecraft undocked at 95:42 GET (8:02 am EDT July 19, 1975). While the spacecraft were in station-keeping mode, the crews photographed them and the docking apparatus, transmitting the pictures live on TV to earth. The Apollo spacecraft then served as an occulting disk, blocking the sun from the Soyuz and simulating a solar eclipse the first man-made eclipse. Leonov and Kubasov photographed the solar corona as the Apollo backed away from the Soyuz and toward the sun. The two spacecraft then redocked at 8:34 am EDT with the Apollo maneuvering and the Soyuz docking system active while good quality TV was transmitted to earth. The second docking was not as smooth as the first because a slight misalignment of the two spacecraft caused both to pitch excessively at contact.

Final undocking also with the Soyuz active went smoothly and was completed at 11:26 am. As the spacecraft separated, the two crews performed the ultraviolet atmospheric absorption experiment, making unsuccessful data measurements at 150 m and then moving to a distance of 500 and 1,000 m, where data were successfully collected. The Apollo maneuvered to within 50 m of Soyuz and took intensive still photography of the Soyuz. Separation maneuvers to put the two spacecraft on separate trajectories began at 2:42 pm with a reaction-control system burn. With the maneuvers completed, Leonov told the Apollo crew, “Thank you very much for your very big job….It was a very good show.” Brand answered, “Thank you, also. This was a very good job.”

Soyuz Orbit and Landing: Soyuz 19 remained in orbit nearly 30 hrs after the undocking. The cosmonauts conducted biological experiments with microorganisms and zone-forming fungi. At 2:39 am EDT 21 July the Soyuz crew closed hatch 5 between their orbital vehicle and descent module and began depressurizing the orbital module. Braking burns of the descent engines began at 6:06 am when the spacecraft was 772 km from the Apollo. The 194.9-sec burn slowed the spacecraft to 120 km per sec. After another burn to stabilize the spacecraft the orbital and descent modules separated over Central Africa.

While Soviet viewers watched the first landing of a Soviet spacecraft televised in real time, the main parachute deployed at 7 km and jettisoned before the soft-landing engines fired. Soyuz 19 landed about 11 km from the target point northeast of Baykonur Cosmodrome at 6:51 am EDT July 21, after a 142-hr 31-min mission. The rescue helicopter approached the capsule immediately and specialists opened hatch 5. Kubasov stepped out waving to rescue-team members, followed by Leonov, both cosmonauts in apparent good health and spirits. The cosmonauts returned to Baykonur for medical checks and debriefings.

Apollo Postdocking Orbital Activities: Apollo remained in orbit while its crew continued U.S science experiments begun during predocking. Searching for extreme ultraviolet radiation, the ASTP crew marked the birth of a new branch of astronomy when they found, for the first time, extreme ultraviolet sources outside the solar system; some scientists had believed that such sources could never be found. One of the newly discovered sources turned out to be the hottest known white dwarf star. The Apollo detector also revealed the existence of the first pulsar discovered outside the Milky Way. About 200 000 light years from earth’s galaxy, in the Small Magellanic Cloud, it was the most luminous pulsar known to astronomers, 10 times brighter than any discovered so far. After repairing some malfunctioning equipment, the astronauts also mapped x-ray sources throughout the Milky Way.

The crew completed nearly all the 110 earth-observation tasks assigned. Coordinated investigations had been made simultaneously by six groups of scientists on the ground, on ships at sea and in aircraft. The astronauts looked at ocean currents, ocean pollution, desert geography, shoreline erosion, volcanoes, iceberg movements, and vegetation patterns.

On 23 July the command-module tunnel was vented and the crew put on spacesuits to jettison the docking module. The command and service module unlocked from the DM at 3:43 pm EDT, and a 1-sec engine firing put the CSM into a higher orbit (232.2-km apogee, 219.0 km perigee) so that the DM could move ahead. A second maneuver put the CSM in a 223.2-km by 219.0-km orbit. Deorbit began at 4:38 p.m. The command module and service module separated, the drogue and main parachutes deployed normally, and the Apollo splashed down at 224:58 GET (5:18 p.m. EDT July 24) in the Pacific Ocean 163W and 22N, 500 km west of Hawaii. This was the last ocean landing planned for U.S. human space flights; future flights on the Space Shuttle would be wheeled touchdowns at land bases.

The CM landed in “stable 2” position (upside down 7.4) km from the prime recovery ship, U.S.S. New Orleans. After swimmers from the rescue helicopter righted the spacecraft and attached a flotation collar, the Apollo was lifted by crane on to the deck of the recovery ship and Stafford, Brand, and Slayton stepped out to the cheers of the ship’s crew. President Ford telephoned congratulations. During the welcome, the crew was evidently experiencing eye and lung discomfort; subsequent conversations and spacecraft data revealed that, during reentry, the earth landing system had failed to jettison the apex cover and drogues as scheduled and had to be fired manually, without first disabling the reaction-control system thrusters. With the CM oscillating, the thrusters began firing rapidly to compensate, and combustion products including a small amount of nitrogen tetroxide entered through the cabin-pressure relief valves. As soon as the RCS system had been disabled, fresh air was once again drawn into the cabin. The crew members told flight officials that they had put on oxygen masks once the spacecraft had landed, and then activated the postlanding vent system.

Because of the crew’s discomfort, further shipboard ceremonies had been canceled and the crew had been sent to sick bay and then to Tripler Hospital in Hawaii for observation until August 8, 1975.

Primary ASTP mission objectives were to evaluate the docking and undocking of an Apollo spacecraft with a Soyuz, and determine the adequacy of the onboard orientation lights and docking target; evaluate the ability of astronauts and cosmonauts to make inter-vehicular crew transfers and the ability of spacecraft systems to support the transfers: evaluate the Apollo’s capability of maintaining attitude-hold control of the docked vehicles and performing attitude maneuvers; measure quantitatively the effect of weightlessness on the crews’ height and lower limb volume, according to length of exposure to zero-g; and obtain relay and direct synchronous-satellite navigation tracking data to determine their accuracy for application to Space Shuttle navigation-system design. The objectives were successfully completed, and the mission was adjudged successful on August 15, 1975.

For Further Reading:

  • Astronautics and Aeronautics, 1975: Chronology of Science, Technology, and Policy. NASA SP-4020, 1979.
  • Bilstein, Roger E. Stages to Saturn: A Technological History of the Apollo/Saturn Launch Vehicles. NASA SP-4206, 1980.
  • Brooks, Courtney G., Grimwood, James M., and Swenson, Loyd S., Jr. Chariots for Apollo: A History of Manned Lunar Spacecraft. NASA SP-4205, 1979.
  • Ezell, Edward Clinton, and Ezell, Linda Neuman. The Partnership: A History of the Apollo-Soyuz Test Project. NASA SP-4209, 1978.
  • Froehlich, Walter. Apollo Soyuz. NASA EP-109, 1976.
  • Shepard, Alan, and Slayton, Deke. Moonshot: The Inside Story of America’s Race to the Moon. New York: Turner Books, 1994.

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Updated October 22, 2004
Charles Redmond, Author
Steven J. Dick, NASA Chief Historian
Steve Garber, NASA History Web Curator
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