Venera 11 arrived at Venus after two course corrections on 16 September and 17 December 1978. On 23 December 1978, the lander separated from the flyby probe and entered the Venusian atmosphere two days later at a velocity of 11.2 kilometers/second. The lander probe descended through the atmosphere using a system of three progressively larger parachutes (areas of 1.4 m², 6 m², and 24 m²). At an altitude of 46 kilometers, the final parachute was jettisoned and the lander effectively dropped the rest of the way—for 52 minutes 58 seconds—guided only by a circular airbrake (with flaps). During this phase the lander carried out chemical analyses of the composition of the atmosphere and clouds, spectral analyses of the scattered solar radiation in the atmosphere, studied the electrical discharges in the atmosphere, and measured temperature, pressure, and windspeeds. The lander safely landed on Venus at 03:24 UT on 25 December 1978, impacting at a velocity of approximately 8 meters/second. Landing coordinates were 14° S / 299° longitude. Within 32 seconds, the imaging system and the soil sampling system simultaneously began operation. The latter collected soil for chemical and physical analysis, but soil analysis was unsuccessful because the soil was not properly deposited to an examination container for analysis (probably due to leaking air which disturbed the soil). The lander also failed to take color panoramas of the Venusian surface due to unopening of the lens covers of the camera system. The lander relayed information for a total of 95 minutes, the point of transmission cutoff being a function of the range of visibility of the flyby probe. The spectrophotometer on Venera 11 reported that only 3–6% of sunlight actually reached the Venusian surface. One of the odd findings was its recording of a loud noise some 32 minutes after landing.
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
Image
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
<!-- image -->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.