Soyuz 20

Soyuz 20 (Russian: Союз 20, Union 20) was an uncrewed spacecraft launched by the Soviet Union. It was a long-duration test of the Soyuz spacecraft that docked with the Salyut 4 space station. Soyuz 20 performed comprehensive checking of improved on-board systems of the spacecraft under various flight conditions. It also carried a biological payload. Living organisms were exposed to three months in space. The primary goal of the mission was to test hardware modifications to the Soyuz 7K-T spacecraft that would extend its operating life from two to three months in preparation for long-duration Salyut crew residencies.

Soyuz 20

Mission type	Orbital test flight
Operator	Soviet space program
COSPAR ID	1975-106A
SATCAT no.	8430
Mission duration	90 days, 11 hours and 47 minutes
Orbits completed	1470
Spacecraft properties
Spacecraft	Soyuz 7K-T No.8
Spacecraft type	Soyuz 7K-T/A9
Manufacturer	NPO Energia
Launch mass	6,570 kg (14,480 lb)[1]
Landing mass	2,800 kg (6,200 lb)
Start of mission
Launch date	17 November 1975, 14:36:37 UTC
Rocket	Soyuz-U
Launch site	Baikonur 1/5[2]
End of mission
Landing date	16 February 1976, 02:24 UTC
Landing site	56 km at the southwest of Arkalyk, Kazakhstan
Orbital parameters
Reference system	Geocentric orbit[3]
Regime	Low Earth orbit
Perigee altitude	199.7 km (124.1 mi)
Apogee altitude	263.5 km (163.7 mi)
Inclination	51.6°
Period	88.8 minutes
Docking with Salyut 4[4][5]
Docking date	19 November 1975, 16:19 UTC
Undocking date	16 February 1976, 23:07 UTC
Time docked	89 days, 6 hours and 48 minutes
Soyuz programme ← Kosmos 772 Soyuz 21 →

Mission parameters

• Mass: 6,570 kg (14,480 lb) ^[1]
• Perigee: 199.7 km (124.1 mi)^[3]
• Apogee: 263.5 km (163.7 mi)
• Inclination: 51.6°
• Period: 88.8 minutes

Return

It was recovered on 16 February 1976 at 02:24 UTC.^[1]