The space race between the U.S. and the Soviet Union made immense progress possible in the field. Reaching our moon first drove most of the competition, won eventually by the U.S. when astronauts of the Apollo 11 mission set foot on the moon.
Once that had been achieved, human beings dared to look further to the outer planets and even beyond. Pioneer 10 was the first NASA mission to the outer planets and its primary objective was to fly by Jupiter, the largest planet in the solar system.
Series of firsts
Launched 50 years ago on March 2, 1972, Pioneer 10 had notched up a number of firsts even before its encounter with Jupiter. As the first spacecraft to use all-nuclear electrical power, Pioneer 10 carried four plutonium generators. The first spacecraft to be placed on a trajectory to escape into interstellar space, Pioneer 10 became the first spacecraft to fly beyond Mars and the first to fly through the main asteroid belt on its way to Jupiter.
Pioneer 10’s tryst with Jupiter began in November 1973, a little over one-and-a-half years from its launch. Even at a distance of 11 million km, the spacecraft began detecting intense radiation and it was revealed that Jupiter’s magnetosphere, much more stronger than that of Earth’s, extended 6.9 million km towards the sun.
Great Red Spot
The Great Red Spot, a storm on Jupiter that is wider than the Earth, came into Pioneer 10’s view as the spacecraft drew closer to the planet. Data from Pioneer 10 published in April 1974 suggested that the centuries old anticyclonic storm was likely a towering mass of clouds.
Pioneer 10 made its closest approach with the biggest planet in our solar system on December 4, 1973. Moving at a speed of 1,26,000 km/hour, the spacecraft whizzed by the giant planet at a distance of about 1,31,000 km.
The spacecraft, however, just managed to survive. Having absorbed radiation that is over a thousand times the lethal dose for a human, some of its transistor circuits were fried, optics were darkened, and there were other unwanted side effects too.
Need for protection
Pioneer 10’s brief tour of Jupiter ended officially on January 2, 1974. As it continued on its trajectory, changes induced by radiation on its systems disappeared in the months that followed. The damage caused served as a learning as it was made abundantly clear that future missions to the outer planets would require enhanced protective equipment.
The probe’s encounter with Jupiter was a great success. Apart from slow-scan images of the planet, data returned also helped us learn that Jupiter’s magnetic field is tilted 15° to its axis of rotation. The presence of helium in the atmosphere and the suspicion that this gas giant was a predominantly gaseous world were also confirmed.
Pioneer 10 ticked more firsts as it crossed the orbits of Saturn in 1976, Uranus in 1979 and Neptune in 1983. While routine contact was stopped in March 1997, the last of the intermittent contact received from Pioneer 10 was in January 2003.
As it continues in the general direction of the red star Aldebaran that forms the eye of the Taurus constellation, Pioneer 10 has the sun and what was once home in its rear view. The Pioneer missions (Pioneer 10 and Pioneer 11) were true to their name, serving as trailblazers and laying the groundwork for future missions like Voyager 1, Voyager 2, Cassini, and more.