Forty years ago, a trailblazing new spacecraft left Earth and boldly went where no probe had gone before.
Launched on Apr. 5, 1973, NASA's Pioneer 11 and its twin probe, Pioneer 10, were the first spacecraft to ever venture beyond the asteroid belt and into the outer solar system. Pioneer 10, launched a year before Pioneer 11, was sent on a more dangerous mission with more unknowns. It become the first probe to pass through the asteroid belt, reach Jupiter and eventually shoot on a trajectory taking it out of the solar system. Pioneer 11 was meant as a backup to its twin and built on its success, reaching the ringed world Saturn in addition to the places Pioneer 10 visited.
Along the way, the two spacecraft helped astronomers understand a great deal about our local solar system. They each carried 11 instruments, allowing them to make measurements of the sun's radiation and determine the odds of safely navigating the asteroid belt. (Despite what C3PO and Star Wars will tell you, asteroid belts are actually quite spacious.) But for a spacecraft traveling tens of thousands of kilometers per hour, even a 0.5-mm-size speck could be destructive. Scientists calculated that Pioneer 10 had a 90 percent chance of passing safely through the asteroid belt but the definitive proof would come from doing just that. To much relief at mission headquarters, Pioneer 10 and 11 did just that.
The Pioneers were pioneers in more ways than one: They paved the way for NASA's subsequent and far more ambitious twin probes, Voyager 1 and 2, which launched in 1977 and toured the outer planets. Engineers used Pioneer 10 and 11 to test their engineering, hardware, and scientific knowledge in order to ensure that the Voyager mission didn't hit any snags.
The Pioneer missions didn't carry the great camera systems of later spacecraft, using simple photo-polarimeters that could only record two wavelengths – red and blue – and produce pictures by painstakingly scanning a view line by line. Despite these drawbacks, the probes produced unparalleled photographs for their time and here we take a look at some of the best pictures and science from these vanguards.
Above:Approaching and Departing Jupiter
Pioneer 10 was the first spacecraft to reach the largest planet in our solar system, Jupiter. Though they seem fairly low-res, most of the images above far exceeded those from ground-based telescopes made until that point.
This being the first real approach to a gas giant, scientists didn't know exactly what to expect. As Pioneer 10 neared Jupiter, its instruments started reading radiation levels 10 times higher than those predicted, and the team feared the spacecraft would get fried. When it appeared that all was lost, the radiation suddenly leveled out and scientists realized that the probe had merely passed through intense radiation belts around Jupiter. Though the radiation destroyed a couple instruments, most survived and people back on Earth were treated to a never-before-seen spectacle: the crescent sunrise at Jupiter.
Image: NASA