The Pioneer Anomaly, a 30-Year-Old Cosmic Mystery that Illustrates Dedication To The Scientific Method
Posted by pwl on December 17, 2010
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.
“1998 was a very interesting year, because right when we made the Pioneer anomaly known, there was the discovery of dark energy,” Turyshev explained. “So basically we realized that the universe accelerates because of dark energy, and people were ecstatic, saying, ‘look, we see something very exciting in the solar system, and maybe we need to modify gravity and all of that will go away, and Einstein and Newton will be, you know, dethroned.’
Five years have passed. Using the telemetry data, the two scientists created an extremely elaborate “finite element” 3-D computer model of each Pioneer spacecraft, in which the thermal properties of 100,000 positions on their surfaces are independently tracked for the duration of the 30-year mission. Everything there is to know about heat conduction across the spacecraft’s surfaces, as well as the way that heat flow and temperature declined over time as the power of the generators lessened, they know. The results of the telemetry analysis? “The heat recoil force accounts for part of the acceleration,” said Turyshev. They wouldn’t tell me how significant a part. (Turyshev: “We’d like to publish that in the scientific literature.”) But according to Toth, “You can take it to the bank that whatever remains of the anomaly after accounting for that thermal acceleration, it will at most be much less than the canonical value of 8.74 x 10-10 m/s2, and then, mind you, all those wonderful numerical coincidences people talk about are destroyed.”
“Actual analysis of the data finally began one year ago, and Toth and Turyshev expect to publish their results in about six months.”
Now that is stunning! All those years just collecting all the data and correcting the errors and ideas to only begin “the calculations for the jump to light speed” (sorry had to include a Star Wars reference here for fun) a year ago!!! Wow. Sounds just like climate science! We’ve not even got the data for the climate of Earth computations yet!!! Must have more data! Must have accurate data! Must eliminate all errors!!!
“Furthermore, he told me, he and Turyshev have been re-addressing the question of which direction the anomalous acceleration points in. It may not be sunward after all, as was always assumed. And a non-sunward acceleration would suggest a non-gravitational cause. “Our results are very suggestive, but I want to wait until we’re completely finished before saying anything more about it. There is a community of physicists interested in the Pioneer anomaly, and I have become quite aware of how desperately sensitive this thing can be.”
“After decades spent thinking, arguing, hoping, and in the words of Turyshev, “making a career off of it,” these scientists’ interest in the Pioneer anomaly has, understandably, accumulated psychological baggage; in the case of many of them, a cloud of emotional investment has formed around the core of objective scientific inquiry. And clouds obscure things.”
“I encourage their work,” he said, “but I’ll be skeptical of the results. And of course, they won’t be entirely sure either. We might just argue back and forth forever.”
Wow, an honest scientist who comprehends The Scientific Method and The Philosophy of Science and how it applies to himself, his community and their work.
“Other physicists are more combative. “Heat? That’s simply not the right explanation. They are wrong,” commented Johan Masreliez, an independent researcher in Washington who supports the expanding spacetime model of cosmology, for which it is crucial that the value of the Pioneer anomaly equals c times H. “But then I’m biased,” he added.”
I’m starting to like these guys methods… and self appraisal abilities.
“In April, Turyshev and Toth published a comprehensive 165-page review article on Arxiv.org called, simply, “The Pioneer Anomaly” to set the stage for the forthcoming publication of their reanalysis. The review begins with two historical anecdotes of obvious pertinence. One is the story of the anomalous precession of Mercury’s perihelion, the seed that 60 years later blossomed into Einstein’s general relativity and the end of physics as it stood. The other is a lesser-known tale of anomalous celestial motion. Around the turn of the 19th century, astronomers noticed that the distant planet Uranus had a funky orbit; it deviated from the path prescribed for it by Newtonian gravity. “Some prominent astronomers suggested that perhaps Newton’s laws break down at great distances from the Sun,” wrote Toth and Turyshev. Speculation of that kind lasted until 1846, at which point another distant planet was discovered right where it needed to be to perturb the orbit of Uranus in just the way it was perturbed. That planet was Neptune, and “Newton’s law was safe.”
Though Turyshev’s and Toth’s results can’t possibly hope to be as rock solid as a new planet, by the sound of things, they themselves have become convinced of the thermal cause of the anomaly, and the sanctity of Newton’s law. “Let me tell you this,” said Turyshev, as I begged him for details about the analysis. “Physics as we know it worked well.”
Ok, the suspense remains forcing us to await their next publication. So we have to wait to learn their actual results… but one thing we do know is that they are following the scientific method very closely, at least from what we can tell from the article’s assertions.
Overall this was a very well written science article and as such I applaud Natalie Wolchover, the author of the popular science article. I also applaud the various people involved in the investigation for their commitment and dedication to The Scientific Method and The Philosophy of Science! Stellar performance guys!