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Pioneer Venus Small Probe (Day)



This spacecraft was the third Small Probe of the Pioneer Venus Multiprobe mission. On this mission four instrumented atmospheric entry Probes were carried by a spacecraft Bus to the vicinity of Venus for descent through the atmosphere to the planetary surface. Two Small Probes entered on the nightside, and one Small Probe and one Large Probe entered on the dayside of the planet. The spacecraft Bus entered the atmosphere and obtained atmospheric composition data until burnup. Investigations emphasize the study of the structural composition and nature of the atmosphere down to the surface, and 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 the Orbiter permitted relating specific local measurements to the general state of the planet and its environment as observed from orbit.

The three small probes were identical and were designated the North Probe (1978-078E), the Night Probe (1978-078F), and the Day Probe (1978-078G). They were all mounted on the Multiprobe Bus (1978-078A) and were released on 20 November 1978. The probes were targeted for different entry points in the Venus atmosphere, all entered on 9 December 1978. The total cost of building and operating the Pioneer Venus probes was $83 million.

Spacecraft and Subsystems

The probe consisted of a spherical pressure vessel surrounded by a forward conical heat shield and an afterbody. The probes had a mass of 90 kg and a diameter of 0.8 m. The pressure vessel held all the scientific instruments and spacecraft systems. It was made of two precisely machined flanged titanium hemispheres joined by bolts with seals between. The seals comprised O-rings and graphoil flat gaskets. The vessel walls were lined on the inside with Kapton blankets and the interior was filled with 102 kPa of Xenon. The instruments were mounted on two beryllium shelves to absorb heat. A small hemispherical antenna protruded from the top of the pressure vessel. The pressure vessel had 7 openings, one for the antenna, three for electrical cables, two for scientific instruments, and one for an access hatch. There were also special diamond and sapphire windows. The probe did not have any thrusters, once released it was on a ballistic trajectory. The aeroshell was a 45 degree blunt cone made of titanium which used a bonded carbon phenolic ablative coating as a heat shield. The aeroshell was permanently attached to the pressure vessel, as was the fiberglass honeycomb afterbody. The small probes did not have parachutes. The small probe carried an atmospheric structure experiment, a nephelometer, a net-flux radiometer, and radio science experiments.

Mission Profile

The Day Probe was released from the Multiprobe Bus at 13:06:29 UT on 20 November 1978. (All times are given in spacecraft time, Earth received time was approximately 3 minutes later.) It was targeted for the dayside at midsouthern latitudes and reached Venus on 9 December 1978. The probe initiated telemetry at 18:35:27 UT and entered the atmosphere (200 km altitude) at 18:52:18 UT. After a 56 minute descent, the probe touched down on the surface (31.3 S, 317 E) at 19:47:59 UT. The probe continued to transmit for another 67 minutes, 37 seconds after landing.

Alternate Names

  • Pioneer Venus 1978
  • Pioneer Venus Probe Day
  • Pioneer Venus Day Probe
  • 12106

Facts in Brief

Launch Date: 1978-08-08
Launch Vehicle: Atlas-Centaur
Launch Site: Cape Canaveral, United States
Mass: 75.0 kg

Funding Agency

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


  • Planetary Science

Additional Information

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



NameRoleOriginal AffiliationE-mail
Dr. Milton A. MitzProgram ScientistNASA Headquarters 
Mr. Fred D. KochendorferProgram ManagerNASA Headquarters 
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

Image of the Pioneer Venus Small Probe (Day) spacecraft

Pioneer Venus Small Probe (Day)

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