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The Pioneer Venus Multiprobe, also known as Pioneer Venus 2 or Pioneer 13, was a spacecraft launched in 1978 to explore Venus as part of NASA's Pioneer program. This part of the mission included a spacecraft bus which was launched from Earth carrying one large and three smaller probes, which after separating penetrated the Venusian atmosphere at a different location, returning data as they descended into the planet's thick atmosphere. The entry occurred on December 9, 1978.

Pioneer Venus Multiprobe
Pioneer Venus Multiprobe
Mission typeVenus atmospheric probes
OperatorNASA / ARC
COSPAR ID1978-078A
SATCAT no.11001
WebsiteNational Space Science Data Center (NASA)
Mission duration4 months, 1 day, 13 hours, 22 minutes
Spacecraft properties
BusHS-507
ManufacturerHughes
Launch mass904 kilograms (1,993 lb)
Dry mass290 kilograms (640 lb) (bus)
315 kilograms (694 lb) (large probe)
3 x 90 kilograms (200 lb) (small probes)
Power241 W
Start of mission
Launch dateAugust 8, 1978, 07:33 (1978-08-08UTC07:33Z) UTC
RocketAtlas SLV-3D Centaur-D1AR
Launch siteCape Canaveral LC-36A
End of mission
Last contactDecember 9, 1978, 20:22:55 UTC (bus)
December 9, 1978, 20:55:34 (1978-12-09UTC20:55:35Z) UTC (day probe)
Orbital parameters
Reference systemHeliocentric
Semi-major axis0.9 astronomical units (130,000,000 km; 84,000,000 mi)
Eccentricity0.19
Perihelion altitude0.69 astronomical units (103,000,000 km; 64,000,000 mi)
Aphelion altitude1.01 astronomical units (151,000,000 km; 94,000,000 mi)
Inclination2.3 degrees
Period284.0 days
Venus atmospheric probe
Spacecraft componentLarge Probe
Atmospheric entryDecember 9, 1978, 18:45:32 UTC
Impact date19:39:53 UTC
Impact site4.4°N 304.0°E / 4.4; 304.0
Venus atmospheric probe
Spacecraft componentNorth Probe
Atmospheric entryDecember 9, 1978, 18:49:40 UTC
Impact date19:42:40 UTC
Impact site59.3°N 4.8°E / 59.3; 4.8
Venus atmospheric probe
Spacecraft componentDay Probe
Atmospheric entryDecember 9, 1978, 18:52:18 UTC
Impact date19:47:59 UTC
Impact site31.3°S 317.0°E / -31.3; 317.0
Venus atmospheric probe
Spacecraft componentNight Probe
Atmospheric entryDecember 9, 1978, 18:56:13 UTC
Impact date19:52:05 UTC
Impact site28.7°S 56.7°E / -28.7; 56.7
Venus atmospheric probe
Atmospheric entryDecember 9, 1978, 20:21:52 UTC
Pioneer (Pioneer Venus)
 

In context


There was also an orbiter launched in 1978, part of the overall Pioneer Venus project along with this entry probe mission. Whereas the probes entered the atmosphere in 1978, the orbiter would stay in orbit throughout the 1980s and the early 1990s (see Pioneer Venus Orbiter). The next major mission was the Magellan spacecraft, which was an orbiter capable of mapping Venus by seeing through its opaque clouds with radar.

Another NASA entry probe mission was the Galileo probe, which was for planet Jupiter.


Spacecraft


Pioneer Venus Bus with probes attached
Pioneer Venus Bus with probes attached

The Pioneer Venus Multiprobe bus was constructed by the Hughes Aircraft Company, built around the HS-507 bus. It was cylindrical in shape, with a diameter of 2.5 meters (8 ft 2 in) and a mass of 290 kilograms (640 lb). Unlike the probes, which did not begin making direct measurements until they had decelerated lower in the atmosphere, the bus returned data on Venus' upper atmosphere.

The bus was targeted to enter the Venusian atmosphere at a shallow entry angle and transmit data until destruction by the heat of atmospheric friction. The objective was to study the structure and composition of the atmosphere down to the surface, the nature and composition of the clouds, the radiation field and energy exchange in the lower atmosphere, and local information on atmospheric circulation patterns. With no heat shield or parachute, the bus made upper atmospheric measurements with two instruments:

The spacecraft operated down to an altitude of about 110 km before disintegrating.


Probes


The spacecraft carried one large and three small atmospheric probes, designed to collect data as they descended into the atmosphere of Venus. The probes did not carry photographic instruments, and were not designed to survive landing – the smaller probes were not equipped with parachutes, and the larger probe's parachute was expected to detach as it neared the ground. All four probes continued transmitting data until impact; however, one survived and continued to transmit data from the surface.


Large probe


Pioneer Venus Large Probe opens its parachute (artist's rendition)
Pioneer Venus Large Probe opens its parachute (artist's rendition)

The large probe carried seven experiments, contained within a sealed spherical pressure vessel. The science experiments were:

This pressure vessel was encased in a nose cone and aft protective cover. After deceleration from initial atmospheric entry at about 11.5 kilometers per second (7.1 mi/s) near the equator on the night side of Venus, a parachute was deployed at 67 km altitude. The large probe was about 150 centimeters (59 in) in diameter and the pressure vessel itself was 73.2 centimeters (28.8 in) in diameter.


Small probes


A small probe (1-antenna, 2-temperature sensor, 3-frontal protection, 4-hermetic container, 5-nephelometer, 6-radiometer)
A small probe (1-antenna, 2-temperature sensor, 3-frontal protection, 4-hermetic container, 5-nephelometer, 6-radiometer)
Entry of Pioneer Venus Multiprobe (comprising 1 large and 3 small probes)
Entry of Pioneer Venus Multiprobe (comprising 1 large and 3 small probes)
Pioneer Venus Large Probe descent sequence
Pioneer Venus Large Probe descent sequence

Three identical small probes, around 0.8 meters (2 ft 7 in) in diameter, were deployed. These probes consisted of spherical pressure vessels surrounded by an aeroshell, but unlike the large probe, they had no parachutes and the aeroshells did not separate from the probes.

The science experiments were:[1]

The radio signals from all four probes were also used to characterize the winds, turbulence, and propagation in the atmosphere. The small probes were each targeted at different parts of the planet and were named accordingly.[2]


Launch


The Pioneer Venus Multiprobe was launched by an Atlas SLV-3D Centaur-D1AR rocket, which flew from Launch Complex 36A at the Cape Canaveral Air Force Station. The launch occurred at 07:33 on August 8, 1978, and deployed the Multiprobe into heliocentric orbit for its coast to Venus.


Arrival at Venus


Prior to the Multiprobe reaching Venus, the four probes were deployed from the main bus. The large probe was released on November 16, 1978, and the three small probes on November 20.

All four probes and the bus reached Venus on December 9, 1978. The large probe was the first to enter the atmosphere, at 18:45:32 UTC, followed over the next 11 minutes by the other three probes. The bus entered the atmosphere at 20:21:52 UTC and returned its last signal at 20:22:55 from an altitude of 110 kilometres (68 mi).

The four probes transmitted data until they impacted the surface of Venus. The Day Probe survived the impact, returning data from the surface for 67 minutes and 37 seconds after reaching the surface.[3]

Pioneer Venus probes and bus: atmospheric entry and impacts (all times in UT)
Large Probe North Probe Day Probe Night Probe Bus
Entry time (200 km) 18:45:32 18:49:40 18:52:18 18:56:13 20:21:52
Impact time 19:39:53 19:42:40 19:47:59 19:52:05 (signal lost at 110 km altitude)
Loss of signal 19:39:53 19:42:40 20:55:34 19:52:07 20:22:55
Impact coordinates 4.4°N 304.0°E / 4.4; 304.0 59.3°N 4.8°E / 59.3; 4.8 31.3°S 317.0°E / -31.3; 317.0 28.7°S 56.7°E / -28.7; 56.7 37.9°S 290.9°E / -37.9; 290.9 (estimated)
Solar Zenith Angle 65.7 108.0 79.9 150.7 60.7
Local Venus time 7:38 3:35 6:46 0:07 8:30

Scientific results


Below the altitude of 50 km the temperatures measured by the four probes are identical to within a few degrees. They are between 448 °C and 459 °C (838 °F and 858 °F) on the surface. The ground pressure is between 86.2 bar and 94.5 bar. Nephelometers identified three cloud layers with different characteristics. The most remarkable discovery was that the ratio of 36argon / 40argon isotopes much higher than in the atmosphere which seems to indicate that the genesis of the Venusian atmosphere is very different from that of Earth. The reconstituted trajectory of atmospheric probes was determined that the wind averaged a speed of 200 m/s in the middle cloud layer at 50 m/s at the base of these clouds and just 1 m/s at the ground. Overall data from airborne sensors confirmed, while specifying the data obtained by the Soviet space probe Venera program that preceded this mission.[4]


Trajectory


Diagram of the PVM's path to planet Venus from Earth in 1978, and this also notes the launch of the Pioneer Venus Orbiter which took place that year also.

Trajectory of Pioneer Venus Multiprobe in 1978
Trajectory of Pioneer Venus Multiprobe in 1978

Graphic overview


Pioneer Venus Multiprobe infographic
Pioneer Venus Multiprobe infographic

See also



References


  1. "Pioneer Venus Project Information". NASA Goddard Space Flight Center. Retrieved 2016-08-17.
  2. Pioneer Venus Probes. NASA Goddard Space Flight Center, 2005.
  3. NASA. Pioneer Venus 2, NASA Science: Solar System Exploration, February 3, 2021. Retrieved 24 April 2022.
  4. Paolo Ulivi et David M. Harland, Robotic Exploration of the Solar System Part 1, The Golden Age 1957–1982, Springer Praxis, 2007 (ISBN 978-0-387-49326-8)



Articles in Science Magazine issue 4401 (1979)



На других языках

- [en] Pioneer Venus Multiprobe

[ru] Пионер-Венера-2

Пионер-Венера-2 — автоматическая межпланетная станция НАСА, запущенная 8 августа 1978 года с целью изучения Венеры. Станция несла четыре спускаемых аппарата, которые успешно выполнили свою миссию. Официальное название — Pioneer Venus Multiprobe, в документах НАСА станция фигурировала также в качестве Pioneer Venus 2 и Pioneer 13.


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