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Pioneer Venus Orbiter

NSSDCA/COSPAR ID: 1978-051A

Description

The Pioneer Venus Orbiter was the first of a two-spacecraft orbiter-probe combination designed to conduct a comprehensive investigation of the atmosphere, surface, and near-space environment of Venus. Pioneer Venus Orbiter measured the detailed structure of the upper atmosphere and ionosphere of Venus, investigated the interaction of the solar wind with the ionosphere and the magnetic field in the vicinity of Venus, determined the characteristics of the atmosphere and surface of Venus on a planetary scale, determined the planet's gravitational field harmonics from perturbations of the spacecraft orbit, and detected gamma-ray bursts. UV observations of comets have also been made.

Spacecraft and Subsystems

The spacecraft was a solar-powered squat cylinder 2.5 m in diameter and 1.2 m high. Its spin axis went through the center axis of the cylinder, it was spin-stabilized at approximately 5 rpm perpendicular to the ecliptic plane. A central thrust tube connected the spacecraft to the launch vehicle. A 1.09 m diameter high-gain parabolic dish antenna was mounted partway up a 2.9 m mast on the top deck of the spacecraft along the spin axis, mechanically despun to remain focused on the Earth. The antenna operated in S- and X-band and had a beamwidth of 7.6 degrees. The top of the mast held an omnidirectional antenna and a backup high gain sleeve dipole antenna.

The instruments and electronic subsystems were mounted on a circular, 4.37 square meter shelf within the spacecraft mounted at the top of the central thrust tube, just below the top deck, except for a magnetometer mounted at the end of a boom extending radially from the top deck to ensure against magnetic interference from the spacecraft. Including the antenna mast, the Orbiter was almost 4.5 meters high. It had a launch mass of 553 kg including 179 kg of rocket propellant. The science payload accounted for 45 kg.

Power was provided by an array of 2 square cm solar cells covering most of the circumference of the spacecraft, totaling 7.4 square meters and providing 312 W at the orbit of Venus. The cells provide 28 V direct current (regulated by shunt limiters) to all systems and science instruments. A backup system, for periods when the spacecraft is shadowed by Venus or not optimally oriented with the Sun, consists of two 7.5 A-hr nickel-cadmium batteries, which are recharged through a small separate solar array.

An 18,000 N solid propellant orbit insertion motor was mounted at the bottom of the cylinder, with the nozzle extending below, centered on the spin axis. Attitude control and spin were controlled by three axial and four radial hydrazine thrusters. Two conical-hemispheric titanium alloy tanks, mounted on the spacecraft thrust tube, each contained 32 kg of hydrazine. Attitude knowledge was provided by a star sensor and Sun sensors. Thermal control was achieved by thermal barriers, thermal louvers, insulating blankets, and heaters.

Communications utilized two redundant S-band transponders, with an uplink (Earth to spacecraft) frequency of 2.115 GHz and 2.295 GHz downlink. There was an aft omnidirectional antenna at the base of the spacecraft in addition to te one one the mast. PVO had a 750 mW X-band transmitter for radio occultation experiments.

A data-handling subsystem digitized and integrated all data. Data was transmitted in major frames, each comprising 64 minor frames of data, and each minor frame had 512 bits. The minor frame could be in one of thirteen formats selected by Earth command. The data would pass through a telemetry processor and the S-band communications system could relay the data to Earth at between 8 and 2048 bits/s. Data was typically transmitted continuously in real time, but data storage was used during occultations (up to 26 minutes). Two data storage units, each with a capacity of 524,288 bits (1024 minor frames) could store data at 672 bits/s or higher for later transmission.

Mission Profile

The Pioneer Venus Orbiter launched on 20 May 1978 at 13:13:00 UT on an Atlas-Centaur from Cape Canaveral. It traveled to Venus on a Type II trajectory, with two small trajectory correction maneuvers on June 1 and November 2. It reached Venus and went into orbit on 4 December 1978 at 15:58 UT.

The initial orbit had a periapsis altitude of 378.7 km, a period of 23.2 hours, and an inclination of 105 degrees. This orbit was altered over the first few weeks to a nominal orbit with an inclination of 105.6 degrees, with periapsis of varying altitude occurring at 17 degrees N latitude, apoapsis altitude of 66,900 km, eccentricity of 0.843, and a period of 24.03 hours. This was maintained through the 243 day nominal mission and early extended mission. From Venus orbit insertion to July 1980 periapsis altitude was held between 142 and 253 km to facilitate radar and ionospheric measurements. Thereafter, the periapsis was allowed to rise (to 2290 km at maximum) and then fall, to conserve fuel.

In May 1992 Pioneer Venus began the final phase of its mission, in which the periapsis was held between 150 and 250 km until the fuel ran out and atmospheric entry destroyed the spacecraft. The last transmission was received at 19:22 UT on 8 October 1992 as the orbit was decaying. The orbiter cost $125 million to build and operate for the first 10 years. For further details see Colin, L. and Hunten, D. M., Space Science Reviews 20, 451, 1977.

Alternate Names

  • 10911
  • PVO
  • Pioneer 12
  • Pioneer Venus 1
  • Pioneer Venus 1978 Orbiter
  • PioneerVenusOrbiter
  • urn:nasa:pds:context:instrument_host:spacecraft.pvo

Facts in Brief

Launch Date: 1978-05-20
Launch Vehicle: Atlas-Centaur
Launch Site: Cape Canaveral, United States
Mass: 374 kg
Nominal Power: 312 W

Funding Agency

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

Disciplines

  • Planetary Science
  • Space Physics
  • Solar Physics

Additional Information

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

 

Personnel

NameRoleOriginal AffiliationE-mail
Ms. Ann C. MerwarthProgram ManagerNASA Headquarters
Mr. Henry C. BrintonProgram ScientistNASA Headquarters
Mr. John W. DyerGeneral ContactNASA Ames Research Center
Mr. Robert W. JacksonGeneral ContactNASA Ames Research Center
Mr. Richard O. FimmelProject ManagerNASA Ames Research Center
Dr. Lawrence ColinProject ScientistNASA Ames Research Center

Selected References

  • Colin, L., Pioneer Venus overview, IEEE Trans. Geosci. Rem. Sens., GE-18, No. 1, 3-4, doi:10.1109/TGRS.1980.350250, Jan. 1980.
  • Nothwang, G. J., Pioneer Venus spacecraft design and operation, IEEE Trans. Geosci. Rem. Sens., GE-18, No. 1, 5-10, doi:10.1109/TGRS.1980.350251, Jan. 1980.
  • Colin, L., Encounter with Venus, Science, 203, No. 4382, 743-745, doi:10.1126/science.203.4382.743, Feb. 1979.
  • Donahue, T. M., Pioneer Venus results: An overview, Science, 205, No. 4401, 41-44, doi:10.1126/science.205.4401.41, July 1979.
  • Colin, L., The Pioneer Venus program, J. Geophys. Res., 85, No. A13, 7575-7598, doi:10.1029/JA085iA13p07575, Dec. 1980.
  • Colin, L., Ed., and D. M., Ed. Hunten, Pioneer Venus experiment descriptions, Space Sci. Rev., 20, No. 4, 451-525, doi:10.1007/BF02186463, June 1977.
  • Fimmel, Richard O., et al., Pioneer Venus, NASA ARC, SP-461, Moffett Field, CA, 1983

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

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 Catalog of Spaceborne Imaging
Venus images in the NSSDCA Photo Gallery
Magellan Project

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