Pioneer Venus Orbiter
Other Name(s)
- PVO
- Pioneer 12
- Pioneer Venus 1
- Pioneer Venus 1978 Orbiter
- 10911
National Affiliation: USA
Launch Date/Time: 1978-05-20 at 13:13:00 UTC
Launch Vehicle: Atlas-Centaur
On-orbit dry mass: 517.00 kg
Nominal Power Output: 312.00 W
Description
The Pioneer Venus Orbiter was the first of a two-spacecraft
orbiter-probe combination designed to conduct a comprehensive
investigation of the atmosphere of Venus. The spacecraft was a
solar-powered cylinder about 250 cm in diameter with its spin axis
spin-stabilized perpendicular to the ecliptic plane. A high-gain
antenna was mechanically despun to remain focused on the earth. The
instruments were mounted on a shelf within the spacecraft except for a
magnetometer mounted at the end of a boom to ensure against magnetic
interference from the spacecraft. 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. From Venus orbit
insertion on December 4, 1978 to July 1980 periapsis 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 1991 the Radar Mapper was
reactivated to investigate previously inaccessible southern portions
of the planet. 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
following August. For further details see Colin, L. and Hunten, D.
M., Space Science Reviews 20, 451, 1977.
