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Pioneer Venus Probe Bus

NSSDCA/COSPAR ID: 1978-078A

Description

The spacecraft was the Bus portion of the Pioneer Venus Multiprobe mission. On this mission four instrumented atmospheric entry Probes were carried by this Bus to the vicinity of Venus and released for descent through the atmosphere to the planetary surface. Investigators emphasized the study of 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 the atmospheric circulation pattern. A sister mission, Pioneer Venus Orbiter, placed an orbiting spacecraft around Venus 5 days before the Probes entered the atmosphere. Simultaneous measurements by the probes and orbiter permitted relating specific local measurements to the general state of the planet and its environment as observed from orbit.

Spacecraft and Subsystems

The Multiprobe Bus had a total mass at launch of 875 kg, of which 585 kg were the attached Large Probe and three Small Probes, 32 kg was hydrazine fuel, and 290 kg was the Bus structure itself. The Bus was a 2.5 meter diameter cylinder on top of which were mounted the Large Probe in the center and the three Small Probes spaced 120 degrees apart around the Large Probe. The total height of the unit from the bottom of the Bus to the top of the large probe was 2.9 meters. Power was provided by a solar array around the outside of the cylinder and batteries. Attitude control and knowledge was provided by radial and aft thrusters and star sensors. Communications were via forward and aft omnidirectional antennae and an aft medium gain horn antenna. The bus was not equipped with heat shield or parachutes, it was only designed to survive upper atmospheric entry. The Large Probe was designed to be launched from the Bus by a pyrotechnic spring-separation system. The Small Probes were held by clamps which could be released by firing explosive nuts. The probes would then spin off the bus tangentially due to the 48 rpm rotation. The Bus carried Ion and Neutral Mass Spectrometers to study the upper atmosphere. The total cost of building and operating the probes was $83 million.

Mission Profile

The Probe Bus was launched on the Pioneer Venus 2 mission on 8 August 1978 at 07:33:00 UT from Cape Canaveral. There was one midcourse correction on 16 August 1978. The trip to Venus took 123 days. The Large Probe separated from the Bus on 16 November and the Small Probes on 20 November. After release of the probes the bus was slowed slightly to fall behind the probes as they headed towards Venus. Two Small Probes entered on the nightside, and one Small Probe and the Large Probe entered on the dayside of the planet. The spacecraft was spin-stabilized at about 48 rpm. The Large Probe took 1-1/2 h to descend through the atmosphere, while the three smaller probes reached the surface of the planet 75 min after entry. The Bus portion of the spacecraft was targeted to enter the Venusian atmosphere at a shallow entry angle and transmit data to Earth until the Bus was destroyed by the heat of atmospheric friction during its descent. At 20:21:52 UT on 9 December 1978 the bus entered the dayside Venus atmosphere (200 km altitude) at 37.9 S, 290.9 E. It returned signals until reaching an altitude of 110 km one minute later at 20:22:55 UT.

Alternate Names

  • Pioneer 13
  • Pioneer Venus 1978
  • Pioneer Venus 2
  • 11001

Facts in Brief

Launch Date: 1978-08-08
Launch Vehicle: Atlas-Centaur
Launch Site: Cape Canaveral, United States
Mass: 380.0 kg

Funding Agency

  • NASA-Office of Space Science Applications (United States)

Discipline

  • Planetary Science

Additional Information

Questions or comments about this spacecraft can be directed to: Dr. David R. Williams.

 

Personnel

NameRoleOriginal AffiliationE-mail
Mr. Fred D. KochendorferProgram ManagerNASA Headquarters 
Dr. Robert E. MurphyProgram ScientistNASA Headquartersrmurphy@ltpmail.gsfc.nasa.gov
Dr. Lawrence ColinProject ScientistNASA Ames Research Center 
Mr. Charles F. HallProject ManagerNASA Ames Research Center 

Selected References

Donahue, T. M., Pioneer Venus results: An overview, Science, 205, No. 4401, 41-44, July 1979.

Colin, L., The Pioneer Venus program, J. Geophys. Res., 85, No. A13, 7575-7598, Dec. 1980.

Colin, L., Ed., and D. M., Ed. Hunten, Pioneer Venus experiment descriptions, Space Sci. Rev., 20, No. 4, 451-525, June 1977.

Other Pioneer Venus Information/Data at NSSDCA

Pioneer Venus Orbiter
Pioneer Venus Probe Bus
Pioneer Venus Large Probe
Pioneer Venus North Probe
Pioneer Venus Night Probe
Pioneer Venus Day Probe

Read about and/or order the PVO CD-ROM set

COHOWeb - Browse and retrieve Pioneer Venus magnetic field data
SPDF anonymous FTP site

Related Information/Data at NSSDCA

Venus Page
Venus images in the NSSDCA Photo Gallery
Magellan Project
Pioneer Venus heliospheric position

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