The Venera 11 flyby probe entered heliocentric orbit after flying past the planet at a range of 35,000 kilometers. A major course correction on 7 February 1979 (c. 350 meters/second delta-V) was done to ensure ideal conditions for the use of the Soviet-French Signe-2MZ1 experiment to study the localization of gamma-ray bursts, but it exhausted almost all of its propellants. As the distance from the Sun increased, the bus depended on its gyroscopes for orientation. Last contact was on 1 February 1980, probably due to improper orientation. The bus's orbit ranged from 1.715 × 1.116 AU.

Venera 12

Nation: USSR (97) Objective(s): Venus flyby and landing Spacecraft: 4V-1 (no. 361) Spacecraft Mass: 4,457.9 kg Mission Design and Management: NPO imeni Lavochkina Launch Vehicle: Proton-K + Blok D-1 (8K82K no. 296-02 / 11S824M no. 4L) Launch Date and Time: 14 September 1978 / 02:25:13 UT Launch Site: NIIP-5 / Site 81/24

Scientific Instruments:

Spacecraft Bus:

plasma spectrometer
Konus gamma-ray detector
Signe-2MZ1 gamma and x-ray burst detector
DUMS-1 ultraviolet spectrometer
magnetometer
solar wind detectors
cosmic ray detectors

Lander:

imaging system
Sigma gas chromatograph
mass spectrometer
gamma-ray spectrometer
Groza lightning detector
temperature and pressure sensors
nephelometer
anemometer
optical spectrophotometer
remote soil collector
x-ray fluorescence cloud aerosol analyzer
Arakhis x-ray fluorescence spectrometer + drill
PrOP-V penetrometer

Results: Venera 12 was the identical sister craft to Venera 11 with a bus-lander configuration, the latter weighing 1,645 kilograms (mass on the surface of Venus would be 750 kilograms). Launched successfully towards Venus, the spacecraft performed two mid-course corrections on 21 September and 14 December 1978. During the outbound trip one of the telemetry tape recorders failed, leading to more frequent use of the remaining tape recorder to relay information. As planned, on 17 November controllers closed the "curtain" of the radiation heater to begin cooling down the lander. Further such actions (on 9–10 and 13–14 December) brought down the temperature on the lander to a nominal –12.3°C although by the time of atmospheric entry the temperature was up to 5°C. Flying a shorter trajectory than its sister, Venera 12 moved "ahead" of Venera 11, and as with its twin, two days prior to the planetary encounter, the flyby probe released its lander. On 21 December the lander entered the Venusian atmosphere at a velocity of 11.2 kilometers/second and performed a descent profile almost identical to the earlier Veneras 9 and 10 in 1975. Release of the final chute occurred at 46 kilometers altitude and for the next 52 minutes and 11 seconds, the lander descended freely with only some airbraking flaps installed on its circular ring for resistance. A vast amount of information was collected and relayed to the flyby probe.

The lander safely touched down at 03:30 UT on 21 December 1978. Landing coordinates were 7° S / 294° E longitude, about 800 kilometers from its twin. From the ground, the probe relayed data for a record 110 minutes, although like Venera 11, the spacecraft suffered two major failures: its soil sample delivery instrument failed to deposit the soil appropriately for scientific analysis; and the lens cover on the camera failed to release, effectively rendering the color imaging system useless. The flyby probe passed by the planet at a range of 35,000 kilometers after performing its data transmission mission and then entered heliocentric orbit with parameters of 0.715 × 1.156 AU. As with the Venera 11 flyby probe, a major course correction (c. 350 meters/second delta-V) on 5 February 1979 on Venera 12 was designed to ensure proper data collection from the Soviet-French Signe-2MZ1 experiment on the localization of gamma-ray bursts. About a year-and-a-half after launch, Venera 12 was fortuitously in position to study the newly discovered Comet C/1979 Y1 (Bradfield). On 13 February 1980, the spacecraft was properly oriented (with the use of its gyro-platform) to study the comet (which was about 50 kilometers closer to the Sun than the spacecraft). The DUMS-1 ultraviolet spectrometer was used to get a spectral signature of the comet both that day and later on 17 March 1980. In mid-April, the three-axis orientation system on the bus failed and the spacecraft was spin-stabilized, which prevented further communication after a last session on 18 April 1980.

Venera 13

Nation: USSR (98) Objective(s): Venus flyby and landing Spacecraft: 4V-1M (no. 760) Spacecraft Mass: 4,397.85 kg Mission Design and Management: NPO imeni Lavochkina Launch Vehicle: Proton-K + Blok D-1 (8K82K no. 311-01 + 11S824M no. 5L) Launch Date and Time: 30 October 1981 / 06:04 UT Launch Site: NIIP-5 / Site 200/40

Scientific Instruments:

Spacecraft Bus:

magnetometer
cosmic ray detector
solar wind detectors
Signe-2MZ2 gamma-ray burst detector

Lander:

x-ray fluorescence spectrometer + VB02 drill
x-ray fluorescence spectrometer for aerosols
imaging system
pressure and temperature sensors
mass spectrometer
Groza-2 lightning detector
Sigma-2 gas chromatograph
nephelometer
spectrophotometer
Bizon-M accelerometer
humidity sensor
PrOP-V soil mechanical/electrical probe
seismometer

A model of the PrOP-V penetrometer installed on Veneras 13 and 14. Credit: T. Varfolomeyev

Results: Venera 13 was part of the third pair of heavy Venus flyby/lander probes launched towards Venus by the Soviet Union in the 1970s (after Venera 9/10 and Venera 11/12). The Soviets picked the landing site for Venera 13 based on information passed on by NASA from the Pioneer Venus Orbiter vehicle. They were supposed to fly in 1980 but the failures of the soil sampler and cameras on Venera 11/12 forced a longer redesign process and these vehicles—especially the landers (each 1,643.72 kilograms)—may have been the most rigorously tested deep space vehicles ever launched by the Soviets. The "new" spaceships had an improved set of instruments (such as the spectrophotometer, the gas chromatograph, and mass spectrometer) including a redesigned soil sampler as compared with its predecessors. Controllers implemented two mid-course corrections on 10 November 1981 and 21 February 1982. During the outbound phase, there were some anomalies: after the first mid-course correction, for example, there were anomalies detected in two of the science instruments (Konus and RPP-01) and a data tape recorder failed.

The Venera 13 lander separated from its parent on 27 February 1982. The capsule entered the Venusian atmosphere and began relaying atmospheric data back to the flyby probe which continued to fly past the planet after a 36,000-kilometer range encounter. After a roughly 1-hour-long descent, the lander set down on the Venusian surface at 03:57:21 UT on March 1, 1982. Landing velocity was about 7.5 meters/second and landing coordinates were 7.55° S / 303.69° E longitude. The probe continued to transmit for another additional 127 minutes, far beyond the planned lifetime of 32 minutes. The probe found temperature and pressure to be 462°C and 88.7 atmospheres, respectively. Venera 13 repeated the attempts at color surface photography (using red, green, and blue filters) that failed on Venera 11 and 12, and succeeded by relaying to Earth the first color photographs of the surface of Venus. Venera 13 returned eight successive panoramas showing a field of orange-brown angular rocks and loose soil. Successful soil analysis (which failed on Venera 11/12) showed soil similar to terrestrial leucitic basalt with a high potassium content. The flyby module entered a heliocentric orbit after relaying back to Earth all the data collected from the lander. Its engine was fired twice, on 10 June and 14 October 1982, as part of a test to provide engineering data for the anticipated Halley's Comet flyby by the Vega spacecraft. The bus continued to provide data until at least 25 April 1983.

Venera 14

Nation: USSR (99) Objective(s): Venus flyby and landing Spacecraft: 4V-1M (no. 761) Spacecraft Mass: 4,394.5 kg Mission Design and Management: NPO imeni Lavochkina Launch Vehicle: Proton-K + Blok D-1 (8K82K no. 311-02 + 11S824M no. 6L) Launch Date and Time: 4 November 1981 / 05:31 UT Launch Site: NIIP-5 / Site 200/39

Scientific Instruments:

Spacecraft Bus:

magnetometer
cosmic ray detector
solar wind detectors
Signe-2MZ2 gamma-ray burst detector

Lander:

x-ray fluorescence spectrometer + VB02 drill
x-ray fluorescence spectrometer for aerosols
imaging system
pressure and temperature sensors
mass spectrometer
Groza-2 lightning detector
Sigma-2 gas chromatograph
nephelometer
spectrophotometer
Bizon-M accelerometer
humidity sensor
PrOP-V soil mechanical/electrical probe
seismometer

Results: Venera 14 was identical to its twin, Venera 13. The spacecraft carried out two mid-course corrections on the way to Venus, on 14 November 1981 and 25 February 1982. There were some anomalies en route: failures in the Konus device and erratic temperatures detected in the lander module (the outer shell holding the lander). Like Venera 13, one of the data tape recorders also failed. Also, the second mid-course correction imparted slightly lower velocity than expected (a shortfall of 1.9 meters/second). Later analysis indicated a possible failure in the turbopump assembly of the main engine. During flyby and release of the lander, the planned burn of the flyby vehicle was increased by 1 minute due to less than expected thrust, to ensure that the flyby bus did not burn up in the Venusian atmosphere and to give sufficient time to receive data from the lander. The lander probe separated from its flyby parent on 3 March 1982 before the entry cycle began but the flyby vehicle's main engine provided much less impulse than anticipated—a shortage of 56.4 meters/second imparted velocity. Fortunately, this was still enough to make sure that the flyby probe did not impact on Venus but it significantly reduced the relay time for data.

The lander's main parachute opened at an altitude of 63.5 kilometers, thus activating the atmospheric instruments. The parachute was released at an altitude of 47 kilometers, and the 750-kilogram lander fell to the surface using only the atmosphere as a retarding medium. The probe made safe contact with the Venusian surface at 07:00:11 UT on 3 March 1982 and continued 57 minutes of transmissions. Landing coordinates were 13.055° S / 310.19° E longitude, about 1,000 kilometers from the Venera 13 landing site. As with its twin, Venera 14 returned color photographs of its surroundings and examined a soil sample (about one cubic centimeter taken from a 30-millimeter deep sample). Soil was deposited in a chamber sealed off from the outside environment and was then successively transferred through a series of chambers by blowing air until the sample was deposited in its final chamber with a temperature of only 30°C. Here it was examined by the x-ray fluorescence spectrometer. Temperature and pressure outside were considerably higher than at the Venera 13 site: 470°C and 93.5 atmospheres respectively. One minor failing of the mission was that one of the ejected caps from the cameras fell just where the PrOP-V penetrometers, designed to test soil properties, were about to operate; instead of testing the soil, PrOP-V simply tested the material of the lens cap.

The flyby probe meanwhile passed Venus at a range of 36,000 kilometers—much closer than originally planned—and entered heliocentric orbit, continuing to provide data on solar x-ray flares. It performed one trajectory change on 14 November 1982 to provide engineering data for the upcoming Vega missions to encounter Halley's Comet. The bus continued to return data until 9 April 1983. A minor controversy surrounded the later Venera missions when a scientist from the Academy of Sciences' Institute of Space Research, Leonid Ksanformaliti, claimed that images from these missions revealed the possibility of "fauna" on Venus. Despite many Russians and Western analysts who debunked his claims, in a series of articles in 2012, 2013, and 2014 in the official journal of the Academy, Ksanformaliti insisted that the presence of "artificial" and repeating shapes ("stems") in the images from Venera 9, 10, 13, and 14 proved his hypothesis. All his claims, however, could be explained by the technical limitations of transmitting the images back to Earth.

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