In October 1957, the Soviet Union launched the first satellite, Sputnik. For the next 20 years, the Space Race saw the USSR and the USA vie with each other in a series of space spectaculars as each tried to out-do the other to demonstrate their economic and technological superiority, culminating in the American landing on the Moon in July 1969. But during this time, there was also some excellent science being done, which got far fewer headlines. One of the most successful of these was the Soviet program to study the planet Venus.
The Venera 3 probe. NASA photo
The first Sputnik satellite was a simple hollow metal sphere with a radio transmitter inside. The first American satellite, Explorer I, was not much better, though it did carry a Geiger counter that discovered the Van Allen radiation belts. The Russian rockets were much larger and more powerful than the American, though, and the Soviet satellites soon became bigger and more sophisticated. Sputnik 2, launched in November 1957, carried the first living organism into space–a dog named Laika, carried in a pressurized chamber. In May 1958, Sputnik 3 was sent into orbit. Weighing almost a ton and a half, Sputnik 3 carried twelve instruments to study the Earth’s atmosphere, including gas detectors, micrometeorite sensors, radiation-measuring Geiger counters, and cosmic ray sensors. These were powered by chemical batteries, though the radio transmitter utilized solar panels to make electricity from sunlight. The instrument packages were housed in a pressurized container with electric fans to keep the pressure and temperature constant. All of these were vital components for planned interplanetary probes.
After the success of Sputnik 3, the Soviets were ready to attempt to send unmanned probes to the Moon, Mars and Venus. The Venus probes were called Venera.
They were difficult missions. The probes used solid-state electronic transistors, which were new technology at the time. Methods had to be worked out for extremely precise navigation to reach targets that were millions of miles away. The environmental conditions there were completely unknown, and the delicate electronic instruments had to be protected from both extreme heat and extreme cold.
There were many failures. The first two Mars probes, Korabl 4 and 5, failed to reach Earth orbit. Luna 1, intended to fly into the Moon’s surface, missed it entirely and went into orbit around the Sun. But in 1959, the Soviets did have two successes with their Moon probes: Luna 2 impacted on the Moon’s surface and became the first man-made object to reach another solar system body, and Luna 3 orbited the Moon and sent back the first photos of the dark side.
The Venus probe Venera 1 flew past Venus in February 1961, but its radio telemetry systems failed and it sent back no data. In July 1962 the Americans attempted to send their own fly-by mission to Venus, but Mariner 1 failed at launch. In December they tried again, and Mariner 2 became the first spacecraft to successfully rendezvous with Venus. The data sent back by Mariner 2 indicated that Venus had an incredibly hot surface temperature, over 800 degrees, and an incredibly dense atmosphere made mostly of carbon dioxide.
Then followed a long string of failures. The Soviets had designed a generic unmanned probe that could be used, with some modifications, for either Mars or Venus missions. Known as the 2MV, it had a booster section with a rocket engine that could be used for course corrections, a spherical chamber for instrumentation, and a place to carry specialized lander modules. But two attempts to send 2MV probes to Venus in September 1962 both failed at launch. Some modifications were made and the instruments were upgraded, but on its first launch to Venus in February 1964, the new 3MV was destroyed when its rocket booster again failed on takeoff. Another attempt in March reached Earth orbit, but the engine that was to propel it to Venus failed, and it re-entered Earth’s atmosphere and burned up. A month later, a Soviet probe managed to successfully reach Venus, but Zond 1, as it became known, lost communications halfway there. Venera 2, another 3MV originally planned as a Mars mission, was reworked for Venus instead and launched in November 1965, but it also lost radio contact on the way there. Less than a week later, Venera 3, designed as a lander, successfully reached Venus and impacted on the surface, but its telemetry failed and the lander module was unable to send back any photos or data (but Venera 3 did go down in history as the first man-made object to reach the surface of another planet). After much testing, the Soviets discovered that a flaw in the 3MV systems was leading to overheating, which seemed to be the cause of the string of failures.
The first Soviet success came in October 1967, when Venera 4 released its lander into the atmosphere of Venus, where it descended slowly on a parachute and sent back data for 93 minutes. Measurements indicated that the atmospheric pressure on Venus was at least 75 times that of Earth, and the temperature was over 800 degrees F. Venera 4 was crushed by the immense pressure at a height of about 15 miles above the surface. Two days after Venera 4, the American Mariner 5 reached Venus on a fly-by mission, and found that the planet had no magnetic field and no radiation belts, and its mass was about 82% of Earth’s.
The next two missions, Venera 5 and 6, were both launched in January 1969, with a mission profile similar to Venera 4. Both were able to transmit data for about 50 minutes, and detected high winds, up to 225 mph, in the Venusian atmosphere.
Buoyed by these successes, the Soviets planned a surface landing for their next mission. Venera 7 was launched in August 1970 and entered the Venus atmosphere on December 15. Deliberately designed to be simple, it carried only a few instruments, but had been immensely strengthened to withstand the crushing pressures and high temperatures. The probe dropped through the atmosphere for 35 minutes on a parachute before reaching the surface, then transmitted date for another 25 minutes. Venera 7 did not carry any cameras, though it was able to measure the temperature (869 degrees) and the pressure (90 atmospheres) at the surface.
The next Soviet mission to Venus, Venera 8, was not launched until March 1972, reaching Venus three months later. It landed successfully on the daylight side of the planet and transmitted data for 63 minutes. It found the light levels during the Venusian daytime to be roughly the same as an overcast day on Earth, which prompted the Soviets to begin planning for surface photography in future probes.
After Venera 8, the Proton rocket launcher became available, which was able to lift a much heavier load, over five tons. Accordingly, the Venera probes were completely redesigned to carry much more instrumentation, including still cameras and television. Venera 9 landed on Venus in October 1975, sending back ultraviolet photos of the atmosphere and, during its 53 minutes on the surface, the first black and white pictures from Venus, showing nine views of a rocky surface. Venera 10 landed just three days later, and transmitted data and photos for 65 minutes before being destroyed by the harsh surface conditions.
It was then another three years before anyone returned to Venus. In 1978, the US sent two probes, Pioneer Venus 1 and Pioneer Venus 2, to orbit the planet. These used radar waves to penetrate the thick cloud cover and reflect off the hard surface below, giving a 3d topographic map of the Venusian surface. Pioneer Venus 2 also released several small landers which transmitted data from the surface for up to 67 minutes. Radar maps showed the surface of Venus to be much smoother than expected. Also in 1978, the Soviets sent two more landers, Venera 11 and 12. Unfortunately, their camera lens caps became stuck, and neither one was able to transmit any pictures.
After these failures, the Venera probes were once again modified to carry more instruments, including a seismic sensor, a microphone, equipment to take surface and subsurface samples, and new cameras. Both probes landed on Venus in March 1982, less than 600 miles apart from each other. Venera 13 survived at the surface for 127 minutes, taking the first color photos of Venus and collecting several soil and rock samples. Venera 14 survived 57 minutes. The surface soil was found to be basaltic.
The last probes in the Venera series were 15 and 16, both launched in June 1983. Instead of landing modules, Venera 15 and 16 carried radar imaging equipment to map the surface from orbit. They covered about half of the planet’s northern hemisphere, confirming that the surface was much smoother than expected. (It has been postulated that Venus was at one point almost completely resurfaced by volcanic eruptions which erased the craters and other surface features.) Venera 14 also dropped a small lander that did a soil analysis–it was found that the surface of Venus is made of basaltic rock that is similar to that found in volcanic ridges on Earth.
The last Venus mission undertaken by the Soviets was in 1985. Vega 1 and Vega 2 were modified versions of the Venera probe, which added a balloon-carried instrument module that was intended to float in the Venusian atmosphere while transmitting data. The two probes reached Venus in June 1985. The balloons stayed aloft for about two days, travelling almost one-third of the way around the planet and providing data on wind speeds at different altitudes.
In 1989, the Soviet Union collapsed, and in the aftermath, Russia did not have the economic resources to continue its interplanetary program. In 1990, the United States probe Magellan reached Venus on a surface-mapping mission, using high-resolution Synthetic-Aperture Radar to map 98% of the planet’s surface over a period of four years.
Over the next 15 years there were no further missions to study Venus (though the Galieo probe to Jupiter and the Cassini probe to Saturn both made fly-by swings around the planet). It wasn’t until 2006 that the European Space Agency’s probe Venus Express entered orbit with an array of seven scientific instruments. It is still transmitting data today. Venus Express discovered evidence for recent (within 3 million years) volcanic activity on Venus, and also indications of previous liquid oceans.
In 2010, the Japanese Space Agency attempted to put its own probe, Akatsuki, into orbit around Venus, intending to study the planet’s atmosphere for two years. But a valve malfunction prevented the engine from firing, and the probe flew past Venus and into a long orbit around the sun. Japanese engineers are planning to make an attempt to fire the engines again and try to enter Venus orbit when Akatsuki returns to fly by the planet in November 2015.
The surface of Venus, photographed by the Venera 14 probe. NASA photo