| Mission type | Test flight |
|---|---|
| Operator | Soviet space program |
| COSPAR ID | 1975-106A |
| SATCAT no. | 08430 |
| Mission duration | 90 days 11 hours 47 minutes |
| Orbits completed | 1470 |
| Spacecraft properties | |
| Spacecraft | Soyuz 7K-T No.8 |
| Spacecraft type | Soyuz 7K-T/A9 |
| Manufacturer | NPO Energia |
| Launch mass | 6570 kg [1] |
| Landing mass | 2800 kg |
| Dimensions | 7.13 m long 2.72 m wide |
| Start of mission | |
| Launch date | 17 November 1975, 14:36:37 UTC |
| Rocket | Soyuz-U |
| Launch site | Baikonur, Site 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 |
| Apogee altitude | 263.5 km |
| Inclination | 51.6° |
| Period | 88.8 minutes |
| Docking with Salyut 4 | |
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.
