Salyut Program Insignia
Salyut 4 (DOS 4) (Russian: Салют-4; English translation: Salute 4) was a Salyut space station launched on December 26, 1974 into an orbit with an apogee of 355 km, a perigee of 343 km and an orbital inclination of 51.6 degrees. It was essentially a copy of the DOS 3, but unlike its ill-fated sibling it was a complete success. Three crews attempted to make stays aboard Salyut 4 (Soyuz 17 and Soyuz 18 docked; Soyuz 18a suffered a launch abort). The second stay was for 63 days duration, and an unmanned Soyuz capsule remained docked to the station for three months, proving the system's long-term durability. Salyut 4 was deorbited February 2, 1977, and re-entered the Earth's atmosphere on February 3. Salyut 4 held the record for long-duration missions for a time.


Installed on the Salyut 4 were OST-1 (Orbiting Solar Telescope) 25cm solar telescope, designed at the
Crimean Astrophysical Observatory, and two X-ray telescopes. One of X-ray telescopes, the Filin telescope made observations of several stars. These X-Ray observations - some of the first taken from space, were published for global use. (We had taken X-Ray images of the sun briefly).

While scientists at the time did not know what caused the X-rays. We have come to learn that they are emitted by super dense stars, including neutrons and black holes. This work led to a
succession of X-Ray observatories being launched -- the latest of which is the Chandra.


Length - 15.8 m
Maximum diameter - 4.15 m
Habitable volume - 90 m³
Weight at launch - 18,900 kg
Launch vehicle - Proton (three-stage)
Orbital inclination - 51.6°
Area of solar arrays - 60 m²
Number of solar arrays - 3
Electricity production - 4 kW
Resupply carriers - Soyuz Ferry
Number of docking ports - 1
Total manned missions - 3
Total unmanned missions - 1
Total long-duration manned missions - 2

Visiting spacecraft and crews

Soyuz 17 - January 11 - February 10, 1975
Georgi Grechko
Aleksei Gubarev

Soyuz 18a - April 5, 1975 - Launch abort
Vasili Lazarev
Oleg Makarov

Soyuz 18 - May 24 - July 26, 1975
Pyotr Klimuk
Vitali Sevastyanov

Soyuz 20 - November 17, 1975 - February 16, 1976
no crew

Salyut 4