The Pioneer Spacecraft: Pioneer 10 now soars toward the constellation Taurus, and 11 aims for Aquila
Thirty years ago, NASA scientists noticed that two of their spacecraft, Pioneer 10 and Pioneer 11, were veering off course slightly, as if subject to a mysterious, unknown force. In 1998, the wider scientific community got wind of that veering—termed the Pioneer anomaly—and took aim at it with incessant, mind-blowingly detailed scrutiny that has since raised it to the physics equivalent of cult status. Now, though, after spawning close to 1000 academic papers, numerous international conferences, and many entire scientific careers, this beloved cosmic mystery may be on its way out.
Slava Turyshev, a scientist at the Jet Propulsion Laboratory (JPL) in Pasadena, Calif., and Viktor Toth, a Canada-based software developer, plan to publish the results of their strikingly comprehensive new analysis of the Pioneer anomaly in the next few months. Their work is likely to bring a conclusion to one of the longest and most tumultuous detective stories of modern astrophysics.
NASA launched Pioneer 10 in the spring of 1972 and Pioneer 11 one year later. The spacecraft’s joint mission was to gather information about the asteroid belt, Jupiter, Saturn (in the case of Pioneer 11), and their moons. As they hurtled past those various celestial objects, the probes measured previously unknown properties of their atmospheres and surfaces; they also photographed Jupiter’s Red Spot and Saturn’s rings up close for the first time. Then, after completing their “flyby” missions in the mid-1970s, the Pioneers kept going. Carrying identical plaques depicting a man and a woman, the atomic transition of hydrogen, and the location of our planet within the galaxy—a message to aliens—the probes became the first manmade objects ever to plunge beyond the solar system into the inconceivable cold and dark of interstellar space. 
This is a fascinating story for many reasons: (1) it has parallels to the entire climate debate, (2) complex computer models of various forces of Nature such as gravity and heat, (3) 1,000s of scientific papers peer reviewed none-the-less attempting to find the cause of the anomaly, (4) destruction of the data (almost), (5) refutation upon refutation leading nowhere, (6) a mystery of great complexity, (7) models that are just to inefficient or full of errors, (8) mistaken idea after mistaken idea, (9) complexity, (10) tenacious independent non-official scientific oriented people dedicated to solving the problem on their own time, (11) …, (N) the list of valuable comparisons goes on and on.
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