Venera program

As part of the Venera program (also Wenera , Russian Венера "Venus"), several space probes were launched from the Soviet Union to Venus between 1961 and 1983 . On December 15, 1970, Venera 7 made the first soft landing on an alien planet.

Missions

First generation

Venera 1

In the launch window of 1961, the Soviet Union planned to launch two probes towards Venus. For a long time it was assumed in the west that the probes had a small landing capsule on board, which was supposed to land on Venus and was designed to be able to swim in an ocean (which was supposed to be present on Venus). This assumption was supported by the fact that Soviet emblems such as the Lunik probes were taken with them. The probes were not carrying a lander, but were supposed to attempt a hard impact on Venus' surface.

• Sputnik 7 was launched on 4 February 1961. The probe failed due to the failure of the upper stage of the Molniya carrier rocket the Earth orbit not. The probe had a mass of 6843 kg in orbit together with the upper stage of the rocket (which was not detached).
• Venera 1 took off on February 12, 1961 and left Earth orbit. However, contact with the probe broke off on February 19, 1961 at a distance of 2 million kilometers from Earth. The silent probe passed Venus 100,000 km away on May 20, 1961, making it the first human-made object to come close to Venus. The probe weighed 643.5 kg.

Since the Molnija launcher used at the start had not yet been well tested, three probes were launched in 1962. A landing was planned for two of these three probes and a flyby for one of Venus. The mass of the probes was around 890 kg each. The probes came from the 2-MV project, in which a common bus was developed for a Mars or Venus probe. This bus could then carry either a landing capsule or an instrument package.

• Sputnik 19 , Sputnik 20 and Sputnik 21 took off on August 25, September 1, and September 12, 1962, respectively, but none of them got out of orbit due to the failure of the launcher.

Sputnik 19 and Sputnik 20 were landing probes , while Sputnik 21 was a flyby probe. Technical details were not published, but because of the shared bus, the structure should have been identical to Mars  1.

In 1965, different pairs of probes were sent on their way again: "Venera 2" and "Kosmos 96" were flyby probes, "Venera 3" was supposed to release a landing probe that should then land on the planet's surface. Although only "Venera 2" and "Venera 3" worked partially successfully, the year 1966 still represented the Soviet breakthrough to Venus. The USA had already beaten the Soviet Union: Its first successful Venus flyby was on December 14, 1962 by Mariner  2 .

The probe bus was identical to the one from Zond 1 to Zond 3. A common bus was planned for probes to Mars and Venus. While the Venus probes were incorporated into the Venera program, all but one of the Mars probes was never started. Instead, they started as Zond 1 to Zond 3. The Zond program generally stood for interplanetary probes, the true nature of which the Soviet Union did not want to reveal.

The flyby probes carried various spectrometers and a camera system, which was supposed to make recordings during the flyby. The lander was supposed to stay on the surface for a long time and was equipped with solar cells. He had meteorological sensors and instruments to study the atmosphere.

• Venera 2 took off on November 12, 1965. The 963 kg probe flew past Venus at a distance of 24,000 km on February 27, 1966, but the connection was broken shortly before the flyby, so that no data was received. The cause was overheating of the probe.
• Venera 3 , launched on November 16, 1965, had no contact with the ground station for the same reason when it flew past Venus on March 1, 1966, but the probe automatically disengaged its landing probe, which partially burned up in the atmosphere of Venus hit the surface hard. It was the first human-made object to land on the surface of Venus. The total mass of the probe was 960 kg.
• Kosmos 96 remained in Earth orbit after launch on November 23, 1965 . The probe was probably identical to "Venera 3".

The two probes from 1967 were further developed models of the “Venera 3” and “Kosmos 96”. "Venera 4" was the first completely successful Venus mission of the Soviet Union, although it did not reach the surface of Venus because the high pressure of Venus' atmosphere was not sufficiently well known. Nevertheless, the probe worked for the entire planned time and was able to provide important data on the atmosphere of Venus.

• Venera 4 was launched on June 12, 1967. The transfer probe disconnected a lander on October 18, 1967 at Venus, which successfully transmitted data for 96 minutes up to a height of 24.96 km until the batteries failed (a battery life of 100 was planned Minutes). Since the atmospheric pressure was estimated to be too low, the probe took longer to descend and could therefore not reach the surface in the planned operating time. The last measurement data showed a temperature of 270 ° C and a pressure of 22 bar at 25 km above the surface. The total mass of the probe was 1,106 kg.
• Cosmos 167 did not go beyond Earth orbit on June 17, 1967. The probe was identical to "Venera 4".

In 1969 the Soviet Union made a double launch to Venus for the first time. The two probes were similar to the successful “Venera 4”, but had landing capsules designed for a slightly higher external pressure of 25 bar. But even this was not sufficient, so that the two probes did not reach the Venus floor intact. The parachute system had been improved so that the probes could now get through the atmosphere faster; the battery capacity has also been increased. Nonetheless, both probes are considered a success, because they provided data on the atmosphere as planned - while hanging on a parachute during the descent. The mass of the probes was 1,130 kg each, 405 kg being accounted for by the lander.

• Venera 5 launched on January 5, 1969 and launched a lander on May 16, 1969. This lander could be kept in contact up to a height of 18 kilometers above the surface of Venus for 53 minutes until it was crushed by atmospheric pressure.
• Venera 6 took off on January 10, 1969 and deployed the lander on May 17, 1969. Contact with the lander lasted 51 minutes up to an altitude of 10 km.

With "Venera 7", whose landing probe could withstand a pressure of 180 bar, the Soviet Union achieved the decisive breakthrough. It was the first successful landing on a strange planet. The total mass of the probe was 1,180 kg. A weak signal was received from the surface for 23 minutes, then the lander fell silent. The instrumental equipment, which for Venera 4 to Venera 6 still included numerous experiments to investigate the atmosphere, now had to be limited to a thermometer and a barometer, as the reinforced shielding of the landing capsule required a great deal of weight.

• Venera 7 began the flight to Venus on August 17, 1970. The landing probe of "Venera 7" carried out the first successful landing on Venus on December 15, 1970. The descent to the surface took 35 minutes with data transmitted on the atmosphere. After landing, data could be received from the surface for 23 minutes.

• Kosmos 359 did not reach a transfer orbit to Venus on August 22, 1970 due to a malfunction of the upper stage of the launcher. The probe was probably similar to the "Venera 7".

The two probes launched in 1972 were similar to those from 1970. Now that the ground pressure of 90 bar was known, the shielding of the capsule could be reduced again and more experiments could be carried out. A radio altimeter made it possible to record the movement of the probe over the ground and thus create a height profile. One device chemically detected ammonia , another examined the size and distribution of aerosols in the atmosphere. A gamma ray spectrometer determined the concentration of the elements potassium , uranium and thorium on the ground . Another task was to measure the light conditions on the surface of Venus in order to prepare the next missions equipped with photo cameras. Therefore, the probes had to land on the day side of Venus after all previous landing attempts had been made on the night side. The total mass of the probes was 1,180 kg each, the landing probes each weighed 495 kg and contained the following instruments: temperature, pressure and light sensors, as well as an altimeter, a gamma ray spectrometer and a gas analyzer. Since the "Venera 7", designed for 180 bar, previously only reported a pressure of 90 bar on the ground, this landing capsule was now designed for 120 bar external pressure.

• Venera 8 took off on March 27, 1972. The lander entered the atmosphere of Venus on July 22, 1972 at 08:37 UTC . The entry speed of 41,696 km / h was reduced by the braking to 900 km / h, after which the 2.5 m large parachute opened at a height of 60 km. Data was being transferred during the descent. The probe landed on Venus' day side at 09:32 UTC and discovered that it was as bright on the planet's surface as it was on a cloudy day on Earth, with a visibility of about one kilometer. This made it known that photography was possible on the surface of Venus. The probe transmitted data for a total of 50 minutes, but only 11 seconds of data was sent from the surface.
• Kosmos 482 returned to orbit on March 31, 1972 due to a launcher failure.

Second generation

Model of Venera 10 in an exhibition, the landing capsule above

All previous Venera probes were launched with Molnija rockets and were thus limited to a mass of around 1,180 kg. But now the much more powerful Proton rocket was available, which could carry around 5,000 kg towards Venus. This made far more demanding missions possible, which is why work was carried out on the new heavy Venera probes.

After the launch window in 1973 was left out, " Venera 9 " and "Venera 10" were launched in 1975 , each consisting of an orbiter and a lander . For the first time, the mother probes did not fly past the planet, but instead entered a highly eccentric orbit . The two orbiters, weighing around 2,300 kg (without fuel), measured the planet and provided radar measurements for the first time, as the surface of Venus cannot be seen due to the atmosphere consisting entirely of clouds . The Soviet Union worked with France on these two missions . The landers on these missions were housed in 2.4 m spheres and each weighed 1,560 kg. Various techniques were used to increase the service life on the 475 ° C hot surface; For example, pre-cooling the entire lander to -10 ° C and taking packets with lithium nitrate trihydrate , a salt that melts at 30 ° C and absorbs heat in the process. For the first time, the Lander contained cameras that provided coarse-resolution images of the surface of Venus. These were the very first complete images of the surface of an alien planet. In addition, the lander had a boom on which the composition of the surface was determined by an X-ray fluorescence spectrometer.

• Venera 9 launched on June 8, 1975 and entered orbit around Venuson October 22, 1975. The lander landed on the same day at 32 ° north and 291 ° east and transmitted data for 53 minutes and for the first time some images of the surface to earth. The probe weighed 4,936 kg at launch.
• Venera 10 took off on June 14, 1975, reached Venus on October 25, 1975, and the lander (landing location 16 ° North and 291 ° East) even worked on the surface for 63 minutes. It also provided data and images of the planet's surface. The probe weighed 5,033 kg at launch.

As it turned out later, the end of the transmission was not caused by the failure of the lander, but because the orbiters disappeared behind the horizon as seen from the lander and data could no longer be received. The Venera 9 orbiter worked until March 22, 1976. Both orbiters examined the Venusian atmosphere with cameras and spectrometers. Further experiments were aimed at interplanetary space and the search for gamma-ray bursts.

With the "Venera 11" and "Venera 12" launched in 1978, the Soviet Union then returned to traditional technology: the mother probe flew past the planet and dropped a lander. This allowed longer contact with the lander. Both probes could only transmit data, but no images, because the camera panel could not come off. The probes weighed 4,940 kg each at launch. France and Austria were also involved in both flyby probes .

• Venera 11 left Earth on September 9, 1978 and passed Venus on December 25, 1978. In doing so, it dropped a lander, which entered the atmosphere at 11.2 km / s and hit the surface about an hour later at 7 to 8 m / s. The lander reported 95 minutes of data from the surface, but some instruments malfunctioned.
• Venera 12 took off on September 14, 1978, but the probe reached the planet on December 21, 1978. The lander then transmitted data for 110 minutes before the mother probe went out of range .

The "Venera 13" and "Venera 14" probes each consisted of a flyby stage and a lander. In contrast to their predecessors, the probes again transmitted images from the surface to the earth. This time the images of the surface were taken with high-resolution color cameras. In addition, the landers had sophisticated analysis systems that took soil samples and examined them inside the probe with an X-ray fluorescence spectrometer. The lander weighed 760 kg each. The two mother probes were also used for maneuver tests for the later Vega mission and for solar observations and were equipped with a magnetometer and detectors for cosmic rays, gamma rays and particle detectors.

• Venera 13 took off on October 30, 1981 and passed Venus on March 1, 1982. The landing probe of "Venera 13" transmitted data and images from the surface (landing location at 7.5 ° south and 303 ° east) at an outside temperature of 457 ° C and an atmospheric pressure of 84 bar for 127 minutes (planned were 32 minutes).
• Venera 14 launched on November 4, 1981. The lander was launched on March 3, 1982. The actual landing took place two days later, on March 5, 1982. The lander survived 57 minutes on the surface (landing location 13.3 ° South and 310 ° East) at an outside temperature of 465 ° C and an atmospheric pressure of 94 bar and provided data and pictures.

Radar topography from Venera 15/16

For the first time, "Venera 15" and "Venera 16" no longer sold a lander, but continued the work of "Venera 9" and "Venera 10". Both probes were identical and were based on modified flight platforms from “Venera 9” to “Venera 14”. They consisted of a 5 m long cylinder and a 1.4 m high parabolic antenna with a diameter of 6 m for the Synthetic Aperture Radar (SAR), which was housed at one end of the cylinder. A 1 m parabolic antenna for the radio altimeter was also located at this end of the probe. A bulge at the opposite end of the cylinder supported fuel tanks and propulsion systems. Two solar panels were available for power supply. A 2.6 m antenna attached to the side of the cylinder was used to communicate with the earth. The probes each weighed 4,000 kg.

In total, the probes were able to cover around 30% of the surface with their Synthetic Aperture Radar (SAR), with the help of which one could see under the dense cloud cover of Venus. The maps created by “Venera 15” and “Venera 16” had a resolution of 1 to 2 km and were therefore about 30 times more detailed than those of Pioneer Venus  1. Both probes could only see the northern hemisphere up to about 30 degrees in their elliptical orbit capture north latitude. This corresponds to about 25 percent of the surface of Venus. However, the US Magellan probe, launched six years later, produced global maps of Venus with a resolution of around 100 meters, which eclipsed the Soviet achievements. France and the GDR contributed instruments to the “Venera 15” and “Venera 16” missions.

• Venera 15 launched on June 2, 1983 for Venus. The probe entered orbit on October 10, 1983 and mapped the planet using Synthetic Aperture Radar until 1984 .
• Venera 16 left Earth on June 7, 1983 and began mapping the planet on October 14, 1983. Contact with "Venera 16" ended on July 12, 1984.

Later missions

From 1984 to 1986 there were two other Soviet missions, Vega 1 and 2 . Both were able to successfully complete their missions.

Venera D

Venera D is a concept for a Venus probe that Lavochkin would build and that should not start before 2025. The probe would consist of an orbiter, a lander, and a balloon floating in the atmosphere. The lander would examine the atmosphere, look for volcanic activity, photograph the surface, and be able to survive for several hours on the surface of Venus.

Summary

Positions of the landed Venera and Vega probes

The exploration of Venus is one of the highlights and highlights of Soviet space travel . In 1966 the Soviet Union achieved its first partial successes, then in 1970 its final breakthrough with the first landing on another planet. After 1972 the technology had matured to such an extent that no missions failed. In 1975 the Soviet Union dispatched the first orbiter to begin radar mapping the planet. Mapping of the planet was not completed by the Soviet Union.

Even so, in the mid-1980s, Venus was considered so well explored that the Soviet Union turned to other destinations. By the end of the 20th century there was only one other Venus mission, the US Magellan , which completed the mapping of the planet.

In the new millennium there are new efforts to explore Venus, primarily from Europe with the successful Venus Express probe (2006-2014) and from Japan with Akatsuki , which was able to swing into Venus orbit in 2015 on a second attempt. Russia also wants to continue to participate with the Venera-D mission.

See also

• Chronology of the missions to Venus

Web links

Commons : Venera Missions  - collection of pictures, videos and audio files

• Bernd Leitenberger: Missions to Venus (including all Venera missions)
• The Soviet Exploration of Venus (Engl.)
• ESA: Homepage of Venera-D (engl.)
• Space Research Institute of the Russian Academy of Sciences: Description of the Venera-D mission (Russian; MS PowerPoint ; 864 kB)

Individual evidence

1. ↑ The first incomplete image was of Mars (Mars 3, December 2, 1971).
2. ↑ Stephen Clark: US-Russian talks on Venus mission resume. In: Spaceflight Now. November 12, 2015, accessed June 23, 2016 . 
3. ↑ Status Report of the Venera-D Joint Science Definition Team (PDF), 2017.