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The Venera series probes were developed by the
Soviet Union between 1961 and 1984 to gather data from Venus,
Venera being the Russian name for Venus. As with some of the Soviet
Union's other planetary probes, the later versions were launched in
pairs with a second vehicle being launched soon after the first of
the pair.
Ten probes from the Venera series successfully
landed on Venus and transmitted data from the surface, including
the two Vega program and Venera-Halley probes. In addition,
thirteen Venera probes successfully transmitted data from the
atmosphere of Venus.
Among the other results, probes of the series
became the first man-made devices to enter the atmosphere of
another planet (Venera 4 on October 18, 1967), to make a soft
landing on another planet (Venera 7 on December 15, 1970), to
return images from the planetary surface (Venera 9 on June 8,
1975), and to perform high-resolution radar mapping studies of
Venus (Venera 15 on June 2, 1983). So, the entire series could be
considered highly successful. Unfortunately the surface conditions
on Venus are extreme, which meant that the probes only survived on
the surface for a duration of 23 minutes (initial probes) up to
about two hours (final probes).
The first Soviet attempt at a flyby probe to
Venus was launched on 4 February 1961, but failed to leave Earth
orbit. In keeping with the (then) Soviet policy of not announcing
details on failed missions, the launch was announced under the name
Tyazhely Sputnik ("Heavy Satellite"). It is also known as Venera
1VA.
Venera 1 and Venera 2 were intended as fly-by
probes to fly past Venus without entering orbit. Venera 1 was
launched on February 12, 1961. Telemetry on the probe failed seven
days after launch. It is believed to have passed within 100,000 km
of Venus and entered heliocentric orbit. Venera 2 launched on
November 12, 1965, but also suffered a telemetry failure after
leaving Earth orbit.
Several other failed attempts at Venus flyby
probes were launched by the Soviet Union in the early 1960s, but
were not announced as planetary missions at the time, and hence did
not officially receive the "Venera" designation.
The Venera 3 to 6 probes were similar. Weighing
approximately one ton, and launched by the Molniya -type booster
rocket, they included a cruise "bus" and a spherical atmospheric
entry probe. The probes were optimised for atmospheric
measurements, but not equipped with any special landing apparatus.
Although it was hoped they would reach the surface still
functioning, the first probes failed almost immediately, thereby
disabling data transmission to Earth.
Venera 3 became the first manmade object to
impact another planet's surface as it crash-landed on March 1,
1966. However, as the spacecraft's dataprobes had failed upon
atmospheric penetration, no data from within the Venusian boundary
was retrieved from the mission.
On 18 October 1967, Venera 4 became the first
spacecraft to measure the atmosphere of another planet. While the
Soviet Union initially claimed the craft reached the surface
intact, re-analysis including atmospheric occultation data from the
American Mariner 5 spacecraft that flew by Venus the day after its
arrival demonstrated that Venus's surface pressure was 75-100
atmospheres, much higher than Venera 4's 25 atm hull strength, and
the claim was retracted.
Realizing the ships would be crushed before
reaching the surface, the Soviets launched Venera 5 and Venera 6 as
atmospheric probes. Designed to jettison nearly half their payload
prior to entering the planet's atmosphere, these craft recorded 53
and 51 minutes of data, respectively, before their batteries
failed.
The Venera 7 probe was the first one designed to
survive Venus surface conditions and to make a soft landing.
Massively overbuilt to ensure survival, it had few experiments on
board, and scientific output from the mission was further limited
due to an internal switchboard failure which stuck in the "transmit
temperature" position. Still, the control scientists succeeded in
extrapolating the pressure (90 atm) from the temperature data (465
°C (869 °F)), which resulted from the first direct surface
measurements. The Doppler measurements of the Venera 4 to 7 probes
were the first evidence of the existence of high-speed zonal winds
(up to 100 metres per second (330 ft/s)) in the Venus atmosphere
(super rotation).
Venera 7's parachute failed shortly before
landing, fortunately very close to the surface. It impacted at 17
metres per second (56 ft/s) and toppled over, but survived. Due to
the resultant antenna misalignment, the radio signal was very weak,
but was detected (with temperature telemetry) for 23 more minutes
before its batteries expired. Thus, it became, on 15 December 1970,
the first man-made probe to transmit data from the surface of
Venus.
Venera 8 was equipped with an extended set of
scientific instruments for studying the surface (gamma-spectrometer
etc.). The cruise bus of Venera 7 and 8 was similar to that of
earlier ones, with the design ascending to the Zond 3 mission. The
lander transmitted data during the descent and landed in sunlight.
It continued to send back data for almost an hour.
The Venera 9 to 12 probes were of a different
design. They weighed approximately five tons and were launched by
the powerful Proton booster. They included a transfer and relay bus
that had engines to brake into Venus orbit (Venera 9 and 10, 15 and
16) and to serve as receiver and relay for the entry probe's
transmissions. The entry probe was attached to the top of the bus
in a spherical heat shield. The probes were optimized for surface
operations with an unusual looking design that included a spherical
compartment to protect the electronics from atmospheric pressure
and heat for as long as possible. Beneath this was a shock
absorbing "crush ring" for landing. Above the pressure sphere was a
cylindrical antenna structure and a wide dish shaped structure that
resembled an antenna but was actually an aerobrake. They were
designed to operate on the surface for a minimum of 30 minutes.
Instruments varied on different missions, but included cameras and
atmospheric and soil analysis equipment.
The descent craft/lander contained most of the
instrumentation and electronics, and was topped by an antenna. The
design was similar to the earlier Venera 9–12 landers. They
carried instruments to take scientific measurements of the ground
and atmosphere once landed, including cameras, a microphone, a
drill and surface sampler, and a seismometer. They also had
instruments to record electric discharges during its descent phase
through the Venusian atmosphere.
The two descent craft landed about 950
kilometres (590 mi) apart, just east of the eastern extension of an
elevated region known as Phoebe Regio. The Venera 13 lander
survived for 127 minutes, and the Venera 14 lander for 57 minutes,
where the planned design life was only 32 minutes. The descent
vehicles transmitted data to the buses, which acted as data relays
as they flew by Venus.
Venera 15 and 16 were similar to previous
probes, but replaced the entry probes with surface imaging radar
equipment. Radar imaging was necessary to penetrate the dense cloud
of Venus.
The Vega probes to Venus and comet Halley
launched in 1985 also used this basic Venera design, including
landers but also atmospheric balloons which relayed data for about
two days.
There were many scientific findings about Venus
from the data retrieved by the Venera probes. For example, after
analyzing the radar images returned from Venera 15 and 16, it was
concluded that the ridges and grooves on the surface of Venus were
the result of tectonic deformations.
The Venera 9 and 10 landers had two cameras
each. Only one functioned because the lens covers failed to
separate from the second camera on each lander. The design was
changed for Venera 11 and 12, but this change made the problem
worse and all cameras failed on those missions. Venera 13 and 14
were the only landers on which all cameras worked properly;
although unfortunately, the titanium lens cap on Venera 14 landed
precisely on the area which was targeted by the soil compression
probe.
Venera-10
Venera 10 was a USSR unmanned space mission to
Venus. It consisted of an orbiter and a lander. It launched on June
14, 1975 03:00:31 UTC.
The orbiter entered Venus orbit on October 23,
1975. Its mission was to serve as a communications relay for the
lander and to explore cloud layers and atmospheric parameters with
several instruments and experiments:
1.6-2.8 m IR Spectrometer
8-28 ?m IR Radiometer
352 nm UV Photometer
2 Photopolarimeters (335-800 nm)
300-800 nm Spectrometer
Lyman-? H/D Spectrometer
Bistatic Radar Mapping
CM, DM Radio Occultations
Triaxial Magnetometer
345-380 nm UV Camera
355-445 nm Camera
6 Electrostatic Analyzers
2 Modulation Ion Traps
Low-Energy Proton / Alpha detector
Low-Energy Electron detector
3 Semiconductor Counters
2 Gas-Discharge Counters
Cherenkov Detector
The orbiter consisted of a cylinder with two
solar panel wings and a high gain parabolic antenna attached to the
curved surface. A bell-shaped unit holding propulsion systems was
attached to the bottom of the cylinder, and mounted on top was a
2.4 meter sphere which held the landers.
On October 23, 1975, this spacecraft was
separated from the Orbiter, and landing was made with the sun near
zenith, at 0517 UT, on October 25.
A system of circulating fluid was used to
distribute the heat load. This system, plus precooling prior to
entry, permitted operation of the spacecraft for 65 min after
landing. During descent, heat dissipation and deceleration were
accomplished sequentially by protective hemispheric shells, three
parachutes, a disk-shaped drag brake, and a compressible, metal,
doughnut-shaped, landing cushion.
It landed 2200 km from Venera 9 (within a 150 km
radius of 15.42°N 291.51°E), three days after its touchdown. Venera
10 measured a surface windspeed of 3.5 m/s. Other measurements
included atmospheric pressure at various heights, and temperature,
and surface light levels. Venera 10 was the second probe to send
back black and white television pictures from the Venusian surface
(after Venera 9). Venera 10 photographs showed lava rocks of
pancake shape with lava or other weathered rocks in between.
Planned 360 degree panoramic pictures could not be taken because,
as with Venera 9, one of two camera lens covers failed to come off,
limiting pictures to 180 degrees.
Lander Payload:
Temperature and pressure sensors
Accelerometer
Visible / IR photometer - IOV-75
Backscatter and multi-angle nephelometers - MNV-75
P-11 Mass spectrometer - MAV-75
Panoramic telephotometers (2, with lamps)
Anemometer - ISV-75
Gamma ray spectrometer - GS-12V
Gamma ray densitometer - RP-75
Radio Doppler experiment
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