Pioneer Venus project

Pioneer - Venus was a space exploration project of the United States.

Prehistory

In 1962, the U.S. had sent the first spacecraft to Venus by Mariner 2. This determined on Venus has a surface temperature of about 425 ° C, excluded the life on Venus. Thus the interest of NASA declined to Venus and she focused instead on Mars. On Mariner 2 Venus probe Mariner 5 in 1967. Mariner 10 flew in 1974 followed on the way to their final destination, the Mercury, the Venus by and photographed them for the first time.

Meanwhile, the Soviet Union had taken the lead role in the exploration of Venus with the Venera missions.

Mission

In the late 1960s, the National Academy of Sciences of the USA made ​​the suggestion of a double mission to Venus. This proposal had a orbiter, which should map the entire surface with a radar and a probe should expose several insertion capsules in Venusatmospäre order to explore it to the surface. This spacecraft program should fund basic research of Venus and be realized as inexpensive as possible. The program was therefore implemented as Pioneer Mission, whose spin-stabilized spacecraft were cheaper than the 3-axis stabilized probes of other programs. The probes were within the Pioneer series first missions No. 12 and No. 13 (see also Pioneer 10 and Pioneer 11), before they were renamed Pioneer Venus 1 and 2.

Pioneer Venus consisted of two probes. Based both on the lower portion of the satellite bus, which has been used by the communication satellite Intelsat IV. However, the scientific payload of both probes was entirely different:

• Pioneer Venus 1 was 582 kg heavy, 4.2 m high and had a diameter of 2.5 m. You should halt to her solid rocket engine in a highly eccentric orbit around Venus, then map the Venus with radar and when flying through the highest layers of the atmosphere analyze them in order to explore its composition, as well as the interactions of the upper atmosphere with the solar wind.

• Pioneer Venus 2 was 904 kg heavy approximately 3.0 m high and had a diameter of 2.5 m. You should unrestrained enter the atmosphere and analyze them. A few days before this admission, they should issue a large and three small conical daughter probes should also explore the atmosphere of Venus.
• The older daughter had probe 1.5 m in diameter and weighed 316 kg.
• The three little daughter probes were each 0.8 m in diameter and weighed 93 kg.
• After the release of the daughter weighed probes Pioneer Venus 2 or 309 kg, was 1.2 m high and had 2.5 m in diameter.

Course

• Pioneer Venus 1 was launched on May 20, 1978 at 14:13 CET with an Atlas - Centaur rocket from Launch Complex 36 at Cape Canaveral in its transfer orbit to Venus. The probe entered a Venus orbit on 4 December 1978. The ground deepest point of this orbit was in the range 153-300 km, while the ground- highest point was constant at 66,000 km. The radar apparatus could be used in the vicinity of the lowest point of ground to map Venus. Each time the web highest point was passed, made Pioneer Venus 1, a photo of the planet, to investigate the global Venus weather. In June 1980, the fuel became scarce and the path corrections were exposed. Over time increased path interference by the sun path lowest point 2290 km altitude. In 1986 the ground- lowest point to fall again. In 1991, the radar was activated again so far to map unkartierbare areas because had changed by the perturbations of the inclination of the orbit. As of May 1992, the ground- lowest point with the last fuel reserves was held in 150-250 km altitude as long as possible. Then the fuel was consumed, and Pioneer Venus 1 burned up on 8 October 1992 in the Venus atmosphere.

• Pioneer Venus 2 was launched on August 8, 1978 at 8:33 CET clock with an Atlas - Centaur rocket from Launch Complex 36 at Cape Canaveral in its transfer orbit to Venus. On 16 November 1978, the eldest daughter probe was suspended on November 20, 1978 followed by the three little daughter probes. The flyby spacecraft and its four subsidiaries probes occurred on 9 December 1978 in the atmosphere of Venus and investigated it to the surface. They succeeded in one of the three small probes daughter to survive the impact with the surface of about 35 km / h and to send data even 67 minutes after landing. It turned out that it took a full three minutes until the had put dust raised again when serving.

Results

Pioneer - Venus was - against targets - a successful U.S. space research project. The radar map of Pioneer Venus 1 was indeed of poor quality ( with a resolution of about 20 kilometers per pixel point about as good as the map in a world atlas ), but it was the first global map at all. Pioneer Venus 1 also observed the changing winds in the Venus atmosphere over time. Pioneer Venus 2 analyzed the composition of the atmosphere in more detail than all previous probes. The fact that the first U.S. landing Venus came, was as unplanned as that it was the survival time record for Venus Lander in the United States. However, he went back 16 days later to the Soviet Union to the countries of Venera 11, which significantly surpassed the record set by Pioneer - Venus 2 with 95 minutes.

With Pioneer Venus 1, there was a follow-up project under the name of Magellan.