Venera 11

Infobox_Spacecraft
Name = Venera 11


Caption = Venera 11 lander
Organization = USSR
Major_Contractors =
Mission_Type = Flyby and Lander
Satellite_Of = Venus
Flyby_Date = December 25, 1978
Launch = 9 September, 1978 at 3:25:39 UTC
Launch_Vehicle = Proton Booster Plus Upper Stage and Escape Stages
Decay =
Mission_Duration =
NSSDC_ID = 1978-084D
Webpage =
Mass = 4940 kg
Power =
Orbital_elements =
Semimajor_Axis =
Eccentricity =
Inclination =
Orbital_Period =
Apoapsis =
Periapsis = 6.62 RV (flight platform)
Orbits =

The Venera 11 ( _ru. Венера-11) was an USSR unmanned space mission part of the Venera program to explore the planet Venus. Venera 11 was launched on 9 September, 1978 at 3:25:39 UTC.

Separating from its flight platform on December 23, 1978 the lander entered the Venus atmosphere two days later on December 25 at 11.2 km/s. During the descent, it employed aerodynamic braking followed by parachute braking and ending with atmospheric braking. It made a soft landing on the surface at 06:24 Moscow time on 25 December after a descent time of approximately 1 hour. The touchdown speed was 7 to 8 m/s. Landing coordinates are Venus coords and quad cat|14|S|299|E. Information was transmitted to the flight platform for retransmittal to earth until it moved out of range 95 minutes after touchdown.

Flight platform

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 34,000 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. Venera 11 flight platform carried solar wind detectors, ionosphere electron instruments and two gamma ray burst detectors - the Soviet-built KONUS and the French-built SIGNE 2. The SIGNE 2 detectors were simultaneously flown on Venera 12 and Prognoz 7 to allow triangulation of gamma ray sources.

List of flight platform instruments and experiments:
* 30-166 nm Extreme UV Spectrometer
* Compound Plasma Spectrometer
* KONUS Gamma-Ray Burst Detector
* SNEG Gamma-Ray Burst Detector
* Magnetometer
* 4 Semiconductor Counters
* 2 Gas-Discharge Counters
* 4 Scintillation Counters
* Hemispherical Proton Telescope

The mission ended in February, 1980.

Lander

The lander carried instruments to study the temperature and atmospheric and soil chemical composition. A device called Groza detected lightning on Venus. Both Venera 11 and Venera 12 had landers with two cameras, each designed for color imaging, though Soviet literature doesn't 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 evidence of lightning and thunder, a high Ar³⁶/Ar⁴⁰ ratio, and the discovery of carbon monoxide at low altitudes.

List of lander experiments and instruments:
* Backscatter Nephelometer
* Mass Spectrometer
* Gas Chromatograph
* X-Ray Fluorospectrometer
* 360° Scanning Photometer
* Spectrometer (430-1170 nm)
* Microphone/Anemometer
* Low-Frequency Radio Sensor
* 4 Thermometers
* 3 Barometers
* Accelerometer
* PROP-V Penetrometer
* Soil Analysis Device
* 2 Color Cameras