The new design was first flown on the Atmospheric Explorer C and D missions where it was necessary to measure the earth's atmosphere at lower altitudes than satellites had probed before. (Please see the "NASA PLANETARY RESEARCH" page of this website for details about the design.) Matching instruments were eventually flown the Pioneer Venus orbiting spacecraft and the spacecraft "bus". These instruments provided part of the data needed to do the first "local" studies of that planet's ionosphere and its interaction with the sun's solar wind.
Description by NASA of the mission for the main "Bus" and probes
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. The trip to Venus took 123 days.
The Large Probe separated from the Bus on 16 November and the Small
Probes on 20 November. Two Small Probes entered on the night side, and
one Small Probe and the Large Probe entered on the day side of the
planet. The spacecraft was spin-stabilized. 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.
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. The Probes stopped transmitting temperature data
about 15 km above the surface of Venus, but two Probes survived on the
surface and transmitted other data for a matter of seconds to minutes.
The Bus ceased transmitting data at an altitude of about 165 km. The
total cost of building and operating the probes was $83 million.
Description by NASA of the Pioneer Venus "Orbiter"
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 de-spun 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 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. 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.
Description by NASA of the Pioneer Venus "Orbiter"
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 de-spun 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 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. 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.
The science results are widely reported, but here are a few of the references to the initial studies.
Taylor, H.A., Jr., H.C. Brinton, S.J. Bauer, R.E. Hartle, P.A. Cloutier, F.C. Michel, R.E. Daniell, Jr., T.M. Donahue, R.C. Maehl, Ionosphere of Venus: First observations of the effects of dynamics on the dayside ion composition, Science, vol. 203, 755, 1979.
Taylor, H.A., Jr., R.E. Daniell, R.E. Hartle, H.C. Brintonm S.J. Bauer, and F.L. Scarf, Dynamic
variations observed in thermal and superthermal ion distributions in the dayside ionosphere of Venus, Adv. Space Res., 1, 247, 1981.
Here is a link to a NASA website for the mission:
http://www.nasa.gov/mission_pages/
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