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Soyuz-13 flies pioneering astronomy mission

In December 1973, two cosmonauts launched into space aboard a custom-built Soyuz-13 spacecraft, carrying the Orion-2 telescope for astrophysical observations. During the eight-day flight, the overworked crew collected a wealth of ultraviolet data from mysterious and little-known objects in the Universe.


Soyuz-13 mission at a glance:

Spacecraft designation
Soyuz, 7K-T No. 33
Launch vehicle
11A511 (Soyuz)
Launch date and time
1973 Dec. 18, 14:55:00 Moscow Time
Launch site
Landing date and time
1973 Dec. 26, 11:50:35 Moscow Time
Ultraviolet astronomy observations with the Orion-2 telescope
Primary crew
Petr Klimuk (Commander), Valentin Lebedev (Flight engineer)
Backup crew
Yuri Ponomarev (Commander), Valery Yazdovsky (Flight engineer)
Flight duration
7 days 20 hours 55 minutes 35 seconds

Origin of the mission

On July 29, 1972, the failed launch of the Soviet DOS-2 space station resulted in the loss of the second copy of the Orion-1 ultraviolet telescope, which was one of the primary scientific payloads aboard the ill-fated orbital lab. The first instrument had previously been installed on the first Salyut space station and returned very promising data.

Shortly after the botched DOS-2 launch, Vasily Mishin, the Head of TsKBEM design bureau, responsible for the Soviet space program, called Grigor Gurzadyan from the Byurakan Observatory in Armenia, who led the development of the Orion. Mishin offered Gurzadyan another opportunity to fly his relatively compact instrument on one of the Soyuz vehicles freed as a result of the space station loss. The astronomer obviously agreed and immediately departed for Moscow for hammering out the required specifications. While still on the plane, Gurzadyan sketched a more capable instrument, which would be ultimately dubbed Orion-2. Its mass increased from 130 (for the original telescopes on Salyut-1 and DOS-2) to 300 kilograms. Surprisingly, it still could be fit into the Soyuz spacecraft, instead of the much more voluminous space station.

Using the Schmidt-Cassegrain optical system, the Orion-2 was capable of capturing ultaviolet radiation from hundreds of celestial objects similtaneously without filtering out the effects of the Earth’s atmosphere. By varying the exposure from 1 to 18 minutes, the Orion-2 could produce spectra from the brightest objects down to the miniscule 13th magnitude, or thousands of times weaker than visible by the naked eye.

Additionally, the Orion-2 payload included G-27 and G-27A spectrographs for star imaging, as well as the G-35 camera for X-ray imaging of the Sun.

Unfortunately, the capabilities of the Soyuz spacecraft, first of all its life-support system, limited the time available for the observations. (1030) Ultimately, TsKBEM decided to build a brand-new Soyuz vehicle with the production designation 7K-T No. 33 specifically for the Orion-2 mission. (231) This particular configuration afforded a maximum 10-day mission, with around a week fully dedicated to the operation of the telescope, even though at the cost of a considerable workload on the crew of two cosmonauts.


The entire telescope assembly was mounted under a custom-designed unpressurized thermal cupola installed on top of the Habitation Module in place of the docking mechanism. The cupola was designed to protect the sensitive instrument during the ascent through upper atmosphere after the separation of the payload fairing and from heating by the Sun during the orbital flight.

The cosmonauts could control the telescope and roughly point it toward observation targets using a dedicated control console inside the Habitation Module and an optical sight mounted on one of the windows of the module, right next to the control console. Using a special gimbal mechanism, the telescope then performed a more accurate pointing at the target and kept itself steady during the exposure relying on a pair of stars as navigational basis. The telescope could rotate 15 degrees each way along two axis and roll up to 10 degrees.

Two shutters with electric mechanisms in the cupola were designed to open and close on commands from the crew for each observation session. In addition, a backup drive could open the covers and permanently fix them in the open position as a last resort.

The guidance platform of the telescope was designed to keep the instrument stable and pointing in one direction for as long as 30 minutes, or during the entire pass of the spacecraft on the night side of the Earth.

A pair of airlocks was installed in the semi-spherical bulkhead separating the unpressurized telescope section from the pressurized Habitation Module. They were intended for the transfer of exposed film from the telescope into the spacecraft interior for the subsequent return to Earth with the crew. (1030)

Crews for Soyuz-13 mission


Petr Klimuk (left) and Valentin Lebedev during training for the Soyuz-13 mission.

First two crews for the Orion-2 mission were formed at the end of 1972. For the first time in the Soviet practice, they consisted entirely of "civilian" cosmonauts of the TsKBEM design bureau due to the scientific nature of the mission. The first team included Nikolai Rukavishnikov and Valery Yazdovsky. Yuri Ponomarev and Valentin Lebedev made the other crew. However, as the trainsing progressed, the crews were changed in May 1973 to a traditional Soviet arrangement with military pilots as commanders. Valery Yazdovsky got Lef Vorobiev as his commander, while Petr Klimuk was first paired with Ponomarev, who was soon found to be too tall for the Soyuz' cramped cabin and he was replaced with Valentin Lebedev.

Both crews departed Moscow for the launch site in Baikonur on Dec. 7, 1973, where the State Commission overseeing the program met on the same night. Here, totally unexpectedly for many involved, the gathering made a rare decision to appoint Klimuk and Lebedev as the primary crew, demoting Vorobiev and Yazdovsky to the backup role. The sudden decision was apparently caused by the ongoing personality clash between Vorobiev and Yazdovsky, which became apparent enough to interfere with their work. Neither of them would ever be given another chance to fly.

However, the situation got even more complicated, when the newly appointed primary crew appeared awfully underdressed for a windy and cold winter day at the traditional farewell ceremony on the launch pad at Site 1, just 24 hours before the scheduled liftoff. Even before reaching the hotel on the way back from the event, Lebedev started experiencing severe fever and pain in his throat. With his backup essentially banned from the flight, Lebedev surrendered to his physician, who "prescribed" some fever medication and a shot of alcohol. Some 1.5 hour later, Lebedev showed up for the pre-launch medical check and passed it with flying colors until it was turn to check the throat. Amazingly, the stunned doctor cleared Lebedev for flight, likely marking the first case of launching a person into space with a severe cold. (231)

Soyuz-13 flies

Soyuz-13 lifted off on Dec. 18, 1973, at 14:55 Moscow Time with the commander Petr Klimuk and flight engineer Valentin Lebedev onboard. At 15:04 Moscow Time, the spacecraft entered an initial 193.3 by 272.7 kilometer orbit with an inclination 51.6 degrees toward the Equator.

At 21:50 Moscow Time, during the fifth orbit of the mission, the spacecraft performed a planned engine firing, delivering 12 meter per second in velocity change and entering a 226.8 by 272.6-kilometer operational orbit. Thanks to the timing of the launch, these parameters provided periodic nightime period lasting 36 minutes, which was optimal for mission objectives, because the glare from the Sun and reflected light from the Earth did not interfere with the faint starlight.

Soon thereafter, the cosmonauts activated the pyrotechnics freeing the Orion-2 telescope from its launch transport restraints. Then, they performed tests of the instrument and transitioned to routine observations.

Until Dec. 25, 1973, the Soyuz-13 crew conducted 16 lengthy observation sessions with the Orion-2 telescope on the night side of the orbit. A total of 10,000 spectra of various stars and the Sun were captured.

Despite being extremely busy with Orion-2, the crew also used a multi-spectral camera to photograph the Earth's surface in nine optical and near-infrared ranges during daylight. They also used a manual spectrograph to image the Earth's horizon in daylight and at dusk to measure the dust content in the atmosphere. Several life-science experiments were also conducted.

After a week of successful work, it was time to wrap up the work and transfer the exposed film from the vacuum of space into the pressurized compartment. The cassette containing star imagery from the main telescope had been successfully extracted, but the units with observations from G-27, G-27A and G-35 instruments stuck at the entry point into their airlock. The cosmonauts spent much of the night before landing trying to resolve the problem, but to no avail. (231)

The return to Earth was sheduled for the 129th orbit of the Soyuz-13 mission on Dec. 26, 1973. Soyuz-13 initiated the braking maneuver at 11:08:41 Moscow Time, reducing its orbital velocity by 95 meters per second. The separated Descent Module of the Soyuz-13 then successfully landed around 200 kilometers southwest of Karaganda in Kazakhstan, on Dec. 26, 1973, at 11:50 Moscow Time, after a nearly eight-day flight.

The recovered film from the Orion-2 telescope was successfully processed on Jan. 6, 1974. For the first time, Soviet astrophysists had such a massive collection of ultraviolet spectra from faint celestial objects, which was enough for many years of research.

The most interesting were three shots produced on Dec. 22, 1973, imaging areas of the sky around the star Capella. Achieving maximum resolution, the frames captured spectra from around 2,000 stars with only fraction of them registered in contemporary catalogs. Orion-2 also captured the first ultraviolet spectrum of a planetary nebula. Several stars with mysterious spectral characteristics were also identified in the images.

Interestingly, the Soyuz-13 mission coincided with the third expedition aboard NASA's Skylab space station and some of the astronomical observations from the US lab imaged the same astronomical objects, which made it possible to compare the results.

The Orion-2 mission also demonstrated the adaptability of the Soyuz spacecraft for various mission objectives and paved the way for the development of new scientific instruments to be installed on piloted vehicles. (1030)


The article by Anatoly Zak; Last update: January 28, 2024

Page editor: Alain Chabot; Last edit: December 19, 2023

All rights reserved


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A cutaway view of the Soyuz-13 spacecraft. Click to enlarge.


Early sketch of the Orion-2 telescope. Click to enlarge.


Overall design of the Soyuz-13 spacecraft:

  • 1 — Habitation Compartment, BO;
  • 2 — Telescope cupola;
  • 3 — Orion-2 telescope;
  • 4 — Film extraction airlocks;
  • 5 — Window with a navigation aid;
  • 6 — Orion control console.


Click to enlarge.



The Orion-2 payload assembly with (top) and without protective screens.


The optical guide for preliminary pointing of the Orion-2 instruments.


The control console of the Orion-2 instruments.


Lev Vorobiev and Valery Yazdovsky during training for the Soyuz-13 mission.


Petr Klimuk (right) and Valentin Lebedev during training for the Soyuz-13 mission.