 Seal of Venera 11 | |
| Operator | Soviet Academy of Sciences |
|---|---|
| COSPAR ID | 1978-084A 1978-084D |
| SATCATno. | 11020 11027 |
| Mission duration | Travel: 3 months and 16 days Lander: 95 minutes |
| Spacecraft properties | |
| Spacecraft | 4V-1 |
| Spacecraft type | 4V-1 No. 360[1] |
| Bus | 4MV |
| Launch mass | 4,447.3 kg (9,805 lb)[1] |
| BOL mass | 4,715 kg (10,395 lb) |
| Landing mass | 760 kg (1,680 lb) |
| Dimensions | 2.7 m × 2.3 m × 5.7 m (8.9 ft × 7.5 ft × 18.7 ft) |
| Start of mission | |
| Launch date | September 9, 1978 (1978-09-09), 03:25:39 UTC[1] |
| Rocket | Proton-K/D-1 8K82K |
| Launch site | Baikonur81/23 |
| End of mission | |
| Last contact | February 1, 1980[1] |
| Orbital parameters | |
| Reference system | Geocentric |
| Regime | Low Earth |
| Semi-major axis | 6,569 kilometers (4,082 mi) |
| Eccentricity | 0.0312 |
| Perigee altitude | 177 kilometers (110 mi) |
| Apogee altitude | 205 kilometers (127 mi) |
| Inclination | 51.5° |
| Flyby ofVenus | |
| Spacecraft component | Venera 11 flight platform |
| Closest approach | 25 December 1978 |
| Distance | ~35,000 kilometers (22,000 mi) |
| Venus lander | |
| Spacecraft component | Venera 11 descent craft |
| Landing date | 25 December 1978, 03:24 |
| Landing site | 14°S299°E / 14°S 299°E /-14; 299 (nearPhoebe Regio) |
TheVenera 11 (Russian:Венера-11 meaningVenus 11) was aSovietuncrewed space mission which was part of theVenera program to explore the planetVenus. Venera 11 was launched on 9 September 1978 at 03:25:39UTC.[2]
Separating from its flight platform on December 23, 1978 the lander entered theVenus atmosphere two days later on December 25 at 11.2 km/s. During the descent, it employedaerodynamic braking followed byparachute braking and ending with atmospheric braking. It made a soft landing on the surface at 06:24Moscow Time (03:24 UT) on 25 December after a descent time of approximately 1 hour. The touchdown speed was 7 to 8 m/s.[3] Information was transmitted to the flight platform for retransmittal to Earth until it moved out of range 95 minutes after touchdown.[4] Landing coordinates are14°S299°E / 14°S 299°E /-14; 299.[3][5]
After ejection of the lander probe, the flight platform continued on past Venus in a heliocentric orbit. Near encounter with Venus occurred on December 25, 1978, at approximately 35,000 km altitude. The flight platform acted as a data relay for the descent craft for 95 minutes until it flew out of range and returned its own measurements on interplanetary space.[6]
Venera 11 flight platform carried solar wind detectors, ionosphere electron instruments and twogamma ray burst detectors – the Soviet-built KONUS and theFrench-built SIGNE 2. The SIGNE 2 detectors were simultaneously flown onVenera 12 andPrognoz 7 to allow triangulation of gamma ray sources. Before and after Venus flyby, Venera 11 and Venera 12 yielded detailed time-profiles for 143gamma-ray bursts, resulting in the first ever catalog of such events. The last gamma-ray burst reported by Venera 11 occurred on January 27, 1980.
List of flight platform instruments and experiments:[7]
The mission ended in February, 1980. Venera 11 is currently inheliocentric orbit, withperihelion of 0.69 AU,aphelion of 1.01 AU,eccentricity of 0.19,inclination of 2.3 degrees andorbital period of 284 days.
The lander carried instruments to study the temperature and atmospheric and soil chemical composition. A device called Groza was intended to search forlightning on Venus. Both Venera 11 and Venera 12 had landers with two cameras, each designed for color imaging, though Soviet literature does not mention them.Each failed to return images when the lens covers did not separate after landing due to a design flaw. The soil analyzer also failed.A gas chromatograph was on board to measure the composition of the Venus atmosphere, as well as instruments to study scattered solar radiation. Results reported included some evidence of lightning,[8] a highAr36/Ar40 ratio, and the discovery ofcarbon monoxide at low altitudes.[4]
List of lander experiments and instruments:
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