Pioneer 10 soars beyond solar system

The year is 1972 and Richard Nixon has been re-elected president of the United States, “All in the Family” is America’s top TV show, and the Soviet spacecraft Venera 8 lands on the surface of Venus. Almost unnoticed is the March 2 launch of Pioneer 10, a hastily constructed spacecraft whose mission is to survey the giant planet Jupiter.

Twenty-eight years later, most of the events that captured our attention back then have been forgotten, but Pioneer 10 gamely soldiers on, sending back data from beyond the edge of the solar system. Mark Wolverton writes in “The Spacecraft That Will Not Die'” in the Winter 2001 issue of Invention & Technology.

NASA officials approved a Jupiter probe in 1969 that also would assess the hazards posed by the asteroid belt, located between Mars and Jupiter, to spacecraft passing through on their way to the outer planets. There was an urgency to getting the project under way and completed, as the window for launch to Jupiter was coming up in early 1972. It also had to be done on a very slim budget, as most of the NASA budget was being funneled into the high-profile lunar landing program. If it had not been for the perseverance of project manager Charles F. Hall, Pioneer 10 might have remained a dream.

Hall ruthlessly discarded anything that would add weight or cost to the project. The three-axis stabilizer system with multiple thrusters common to spacecraft was scrapped in favor of a simple spin stabilizer similar to a gyroscope, solar panels were replaced by four small nuclear generators each producing 40 watts of power, 150 proposed experiments were pared to 11, and no component was used that had not proved itself on a previous flight.

The final spacecraft, which has been likened to building a car out of whatever parts are available in the local junkyard, weighed only 570 pounds and was 9.5 feet long. Many aerospace experts doubted it could carry out its limited mission.

Pioneer 10 began its mission on March 2, 1972, passing by Mars in June before entering the asteroid belt in mid-July. The spacecraft left the asteroid belt in February 1973, and, contrary to what was feared, had almost no impact damage. Pioneer 10 continued on to Jupiter and arrived in the vicinity in November 1973.

It now faced a new threat, the intense radiation fields of Jupiter that might fry the spacecraft’s electronics. But this fear also proved groundless, and, on Dec. 3, 1973, Pioneer 10 skimmed Jupiter at a little less than 81,000 miles, sending back reams of data and detailed photos in the process. Pioneer 10 had completed the mission it was built to do, but its saga was just beginning.

NASA continued to monitor Pioneer 10 over the years, but interest began to wane except among a few dedicated individuals. Pioneer 10 passed out of our solar system on June 13, 1983, becoming the first human artifact to fly beyond the planets. It sent back the first picture ever taken looking back at the solar system, but its usefulness was steadily diminishing. Its handlers managed to find uses to justify not shutting it down, such as becoming a practice tracking target for the Lunar Prospector Mission and to test advanced communication technology. But the end came on March 31, 1997, a little over 25 years after it was launched as formal support was cut from the program.

Still Pioneer 10 devotees worked on their own time, maintaining the ancient mainframe computer needed to communicate with it, and begged time on the Deep Space Network to send and receive signals. This too will end in about a year as Pioneer’s increasingly weak signal, which takes nearly 10 hours to reach Earth at the speed of light, is almost at the limits of NASA’s capability to pick it up.

Today Pioneer 10 is over 7 billion miles from Earth and speeding into deep space at 27,380 miles per hour. It is heading toward the star Aldebaran, in the constellation of Taurus the Bull, where it should arrive in about 2 billion years. Aboard is a gold-plated disk showing human physiology, the solar system, and giving coordinates for the sun in the Milky Way galaxy. Long after the Earth and its human inhabitants are but a memory, writes Wolverton, Pioneer 10 will be sailing through the cosmos bearing its message to the universe that we once were here.

Clair Wood taught chemistry and physics for more than 10 years at Eastern Maine Technical College in Bangor.