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Where no probe had gone before: 40th anniversary of Pioneer 11


An artist's impression of Pioneer 11. Photo: NASA Ames
An artist's impression of Pioneer 11. Photo: NASA Ames

Daniel Martins, staff writer

April 6, 2013 — 40 years after launch, here's a look back at the part Pioneer 11 played in piercing the mysteries of the solar system.

Pioneer 11 was the first probe to reach Saturn. Photo: NASA Ames
Pioneer 11 was the first probe to reach Saturn. Photo: NASA Ames

It's been forty years since Pioneer 11 blasted off from Cape Canaveral, on April 5, 1973, making a beeline for Jupiter and beyond.

It wasn't the first probe sent from Earth to head that way -- that honour went to sister ship Pioneer 10, launched the previous year.

But Pioneer 11 built on the success of its predecessor, blazing a path that would ensure safe passage to the outer solar system for more advanced probes.

Like its sister ship, Pioneer 11 passed by the Solar System's largest planet -- and did one better by zipping by at only 42,000 km above the giant's colourful cloud-tops, five times closer than Pioneer 10 dared, sending a wealth of data and photographs back to earth.

Using Jupiter's intense gravity well, the probe zoomed to its new destination: Saturn, beautiful and mysterious.

The planet's famous rings were both the probe's target, and a source of controversy within NASA. 

Pioneer 11's handlers wanted to risk the probe on a journey through the inner rings, a potentially dangerous path that would yield a treasure trove of new discoveries.

But the team behind Voyager 2, which was close behind Pioneer 11, had other ideas.

Voyager 2's mission would take it past Saturn and beyond, to Nepture and Uranus. Their planned route would run through Saturn's outer rings --- and they wanted Pioneer 11 to go first, to see if it was safe.

The Voyager 2 team had their way, to the dismay of the Pioneer 11 supporters.

Pioneer 11 wasn't the first probe to fly past Jupiter, but its scans still yielded valuable data. Courtesy: NASA Ames
Pioneer 11 wasn't the first probe to fly past Jupiter, but its scans still yielded valuable data. Courtesy: NASA Ames

"It was a controversial decision at the time," Larry Lasher, Pioneer's last project manager, said in a statement released by NASA. "But with the brave path it forged, Pioneer 11 was proud to contribute to the success of Voyager 2 in its completion of the 'Grand Tour,' and the exploration of two of the outermost planets in the solar system."

Pioneer still lived up to its name, and the "safer" path wasn't a snooze.

The probe discovered two new moons -- and came within 4,000 km of smashing into one, Epimetheus, the day after its discovery. Another moon, Titan, was scanned, and found to be probably too cold to support life.

It also scanned Saturn's magnetic field and magnetosphere, documented heat radiation from the planet's interior, and carried out several other tests that were the first of their kind.

By the time the probe left Saturn and set a course for the edge of our solar system, it had long surpassed its 21-month mission timeline. It continued functioning for decades, before contact was finally lost on Sept. 30, 1995 -- so far away from the earth, its last radio transmission took twelve hours to reach us, travelling at the speed of light.

NASA says it's now believed to be about 13 billion km away from the sun, heading in the general direction of the constellation Scutum.

Not bad for humanity's first true outing to Saturn.

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