Pioneer Venus Mission
Historical Space Explorer Reaches the Second Planet
The goal of the 1978 mission "Pioneer Venus" was to begin studying the shrouded planet both from orbit and from within the atmosphere. Two spacecraft, Pioneer 1 or Orbiter, and Pioneer 2 or Multiprobe, were launched 10 weeks apart and both successfully reached their destinations. According to NASA's Science Mission Directorate, the Orbiter left Earth aboard an Atlas-Centaur launch vehicle on May 20, 1978 and was inserted into an elliptical orbit around Venus on December 4 later that same year. This orbit facilitated the eventual execution of 17 different scientific experiments.
Orbiter's Mission
The hockey-puck-shaped spacecraft bristled with instruments, twelve in all, capable of measuring cloud distribution, IR emissions, UV light and ionospheric particles, as well as study atmospheric composition and temperatures, solar wind and gravitational fields. NASA's official Pioneer Venus Orbiter mission site explains that the Orbiter was able to thoroughly map the clouds, atmosphere and ionosphere. It also mapped the planet's surface by radar. Pioneer 1 communicated back to Earth scientists using S-Band and X-Band radio signals.
Multiprobe's Mission
Pioneer 2, or Multiprobe, launched on August 8, 1978, also aboard an Atlas-Centaur rocket. The Multiprobe spacecraft consisted of a shell vehicle or bus which carried 1 large probe and 3 identical small probes. It's mission was quite aggressive. It was to plunge into the mysterious Venus atmosphere and transmit as much data as possible back to Earth before a glorious death upon surface impact. After arriving safely at the planet and entering orbit, the bus released the large probe on November 16 and the small probes four days later, all of which stayed in orbit for a few weeks. On December 9, all 4 probes entered the atmosphere within 11 minutes of each other, followed shortly after by the bus.
Large Probe Parachutes Down
The large probe, the only one benefiting from a parachute, was equipped with 7 science experiments. It was tasked with studying atmospheric composition, infrared radiation, cloud particles, temperature, pressure and acceleration. It entered the atmosphere on the night side at a blazing 11.5 km/s. At an altitude of 47 km its parachute was deployed, slowing the vehicle down in order to extend the duration of data transmission.
One Small Probe Survived Impact
The 3 small probes entered the atmosphere at different locations around the planet and were named as such. The North probe entered on the day side at about 60 degrees north latitude. The Night probe and Day probe entered on their respective sides of Venus. Each of these probes were equipped with temperature, pressure and acceleration sensors, as well as a radiometer experiment and a nephelometer to study atmospheric particle density. In addition to these measurements that were transmitted back to Earth during the near-one-hour descent, the radio transmissions themselves were used to determine important facts about wind and turbulence. None of the 3 small probes were equipped with parachutes, but incredibly, two of them continued to transmit data for several minutes after surface impact.
Fourteen Years of Discovery
The Orbiter continued its work long after its smaller sister ships destroyed themselves in a literal blaze of discovery. By strategically changing orbits and conserving precious fuel, scientists were able to learn from Orbiter for 14 fruitful years. In August of 1992, the spacecraft's orbit decayed and it burned up in the atmosphere. But all measures, Pioneer Venus was a tremendous success.
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