Today, when we hear the word "Jupiter," the giant gas planet immediately comes to our mind. [Don't take this priceless gift for granted.] Back in 1972, people had very little knowledge about the gas giants. That is why Pioneer 10 and Pioneer 11 were launched. These two small spacecraft produced great advances in our knowledge of the solar system and prepared the way for the Voyagers.
Mission To The Gas Giants
With a mass of only 258kg, the identical Pioneer (Pioneer 10 and Pioneer 11) spacecraft officially started their journey when the Atlas-Centaur rocket lifted off and sent them on their way. Traveling at 50,000 km/h (31,000 mi/h), the Pioneers were the fastest man-made objects at the time. They crossed the moon's orbit in 6 hours and were soon on their way to Jupiter.
Continuing at that speed, the Pioneers arrived at Jupiter in December 1973. Scientists were astounded by the pictures the spacecraft took. It was also discovered that Jupiter has an enormous magnetic field, about 250,000 times as great as Earth. Another major discovery, although already suspected by observations from Earth, was that Jupiter radiates 2.5 times the energy it receives from the sun.
One technique used on the Pioneer mission as well as other missions was to instruct the spacecraft to go behind an object (planet or moon). From the radio waves received on Earth, scientists could determine a lot about the atmosphere and density of the object. The technique was used on Jupiter and several of its moons.
After the visit to Jupiter, Pioneer 10 headed into interstellar space while Pioneer 11 headed for Saturn. By the influence of Jupiter's gravity, Pioneer 11 was accelerated to 55 times the speed of a bullet, 173,000 km/h (107,500 mi/h) [zoom, zoom, zoom]. Having safely passed the asteroid belt, Pioneer 11 took the best, most close-up picture of Saturn to that date, as well as studying the atmosphere, rings, and magnetic field.
A Forgotten Legend
Pioneer 10 and Pioneer 11 are also the first man-made objects to escape the gravity of the Sun. They are now heading into interstellar space. They will continue to travel through space for billions of years until solar dust eventually erodes the spacecraft to nothingness.
As mans' first messengers to the stars, they were each equipped with a metal plate that showed our location in the Universe, the planet's in our solar system, and a picture of a man and a woman. If some extraterrestrial race finds the Pioneer spacecraft they would know who was behind the spacecraft and where to find them. Many critics believed that we should keep our location secret in case the aliens who find it turned out to be hostile [sounds like science-fiction to me], but our desire to know whether other life exists outweighed the risk.
Although extremely successful, the Pioneer's journey became forgotten as Voyagers, a much more sophisticated spacecraft followed them. Nevertheless, the two tiny spacecraft lived up to their names: they were true pioneers, the first to come and pave the way for others to follow.
