Gallery: Best of Pioneer: A Look at Mankind's First Encounters With Jupiter and Saturn
01approaching-and-departing-jupiter
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](http://www.nasa.gov/centers/ames/missions/archive/pioneer10-11.html), 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](http://www.honeysucklecreek.net/dss44/pioneer_missions.html) 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](http://stag-komodo.wired.com/wiredscience/2012/09/voyager-35th-anniversary/), 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](http://www.astrosurf.com/nunes/explor/explor_pioneer.htm) 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](http://solarsystem.nasa.gov/multimedia/display.cfm?Category=Spacecraft&IM_ID=12847)*
02full-face-of-jupiter
Full Face of Jupiter -------------------- Pioneer 11 peers down on Jupiter from above in this image. By building on the lessons of Pioneer 10's flyby, engineers were able to pass Pioneer 11 nearly 10 times closer to the gas giant than its predecessor. The probe went over the planet's pole to avoid its dangerous radiation belts, managing to produce the best pictures of Jupiter seen until then. Using Jupiter's gravity, Pioneer 11 was able to slingshot around the gas giant and travel on to Saturn. *Image: [NASA Ames](http://www.nasa.gov/centers/ames/news/2013/pioneer11-40-years.html)*
03jupiter-rotating
Jupiter Rotating ---------------- Pioneer 10 and 11 were able to teach scientists a great deal about Jupiter. Among other things, Pioneer 10 showed the mighty power of Jupiter's great radiation belts and proved that the planet was producing more heat than it absorbed from the sun. Pioneer 11 mapped the planet in detail including its famous Great Red Spot and was able to calculate the mass of one of its moons, Callisto. *Image: NASA*
04jupiters-main-moons
Jupiter's Main Moons -------------------- The four largest satellites of Jupiter, first spotted by Galileo more than 400 years ago, are seen here with the best resolution obtained from the two Pioneer probes. *Image: [NASA](http://history.nasa.gov/SP-349/p180.htm)*
05saturn-and-titan
Saturn and Titan ---------------- Saturn can be seen here with its largest moon Titan during Pioneer 11's approach. *Image: [NASA Ames](http://www.nasa.gov/centers/ames/news/2013/pioneer11-40-years.html)*
06saturn-through-rings
Saturn Through Rings -------------------- Pioneer 11 was the first spacecraft to pass near Saturn's gorgeous ring system. NASA engineers heatedly debated exactly what route the probe should take at the ringed giant. No one knew what exactly the rings were made of and it was possible that the spacecraft could get damaged by debris. The team decided to just go for it and risk the destruction of the mission for the chance to do great science, and decided to send Pioneer straight through Saturn's mysterious inner rings. But then NASA headquarters overrode the Pioneer team's decision. They wanted to have Pioneer travel on a farther route that would test the path for the later Voyager missions (Pioneer's team members booed when they found out). *Image: [NASA](http://commons.wikimedia.org/wiki/File:P11saturnb.jpg)*
07saturns-rings-2
Saturn's Rings -------------- Pioneer grabbed this great image of Saturn's famous rings and one of its moons, possibly Rhea. During its flyby, the probe crossed the plane of the great rings twice, once inbound and once again outbound. A few minutes after the first ring plane crossing, Pioneer 11 nearly slammed right into a moon. Rates of energetic particle detections dropped dramatically and magnetic readings changed quickly, indicating that the spacecraft had passed right through the magnetic wake of a moon. Two moons are now known to orbit in that area, Epimethius and Janus, and to this day no one knows which one Pioneer nearly hit. *Images: 1) [NASA](http://commons.wikimedia.org/wiki/File:Pioneer_11_f17.gif) 2) A close-up view of Titan that Pioneer made during its flyby [NASA](http://en.wikipedia.org/wiki/File:Pntitan.jpg)*
08pioneer-movie
Pioneer Movie ------------- This is a cute retro video created prior to launch showing animation made by NASA of the Pioneer probes planned flybys of Saturn and Jupiter. *Video: [NASA](http://www.nasa.gov/multimedia/videogallery/index.html?collection_id=14388&media_id=161538491)*
09pioneer-plaque
Pioneer Plaque -------------- Pioneer 10 crossed the orbit of Neptune in 1983, becoming the first probe to leave the vicinity of the solar system's planets. The last signals were received from the probe in 2003, when it was 12 billion km away, or roughly 80 times the distance between the Earth and the sun. Pioneer 11 is currently 13 billion km from the sun and headed in the direction of the constellation Scutum. Both probes have been overtaken by the Voyager spacecraft, which travel faster than them and are the most distant man-made objects ever built. Both Pioneer probes carry a small plaque designed by Carl Sagan and Frank Drake, drawn by Sagan's then-wife Linda Salzman Sagan. The drawings are meant to convey to anyone who sees them where these spacecraft came from and the types of beings who built them. Though its possible that an alien race may one day discover the plaques, whether or not they will be able to understand them is anyone's guess. [](http://stag-komodo.wired.com/images_blogs/wiredscience/2013/04/Pioneer10-plaque.jpg) *Image: 1) The plaque attached to one of the Pioneer probes [NASA](http://en.wikipedia.org/wiki/File:GPN-2000-001621-x.jpg) 2) The full plaque [NASA](http://en.wikipedia.org/wiki/File:Pioneer10-plaque.jpg)*
