Slashdot Mirror
Pioneer Anomaly Solved
First time accepted submitter gstrickler writes "After years of work recovering and analyzing old mission data and vehicle schematics, a just published analysis(Pdf) provides strong evidence for anisotropic thermal radiation being the source of the slowing of the Pioneer 10 and 11 spacecraft. The theory isn't new, but the recovered data and new analysis provide solid evidence that at least 80% of the deceleration is accounted for by anisotropic thermal radiation. Members of The Planetary Society were instrumental in recovering the data and helping fund the analysis. The lesson is, in space, it matters what direction your heat radiating surfaces point."
There's an acceleration vector for every force vector and a net acceleration and a net force vector. They're mathematically equivalent. You could also look at it as a sum of momentum delta vectors. How is the electromagnetic force conveyed? By a photon exchanging momentum. So is force something that only exists as an effect of adding up all the changes in momentum, or vice versa? Neither, both are correct viewpoints. Have a nice day.
The enemies of Democracy are
Am I arrogant for saying "wasn't this obvious?"
Not really as long as you realize that some things seem obvious once you know they're true... Or as long as you just mean "obvious possibility".
It's not like they didn't know that if there was a favored direction for the emission of radiation that this would affect the velocity of an object. The concept of a photon drive existed for decades before the Voyagers were launched. It's just that it was though that whatever net force there was would be essentially zero. Assume a uniform, spherical Voyager craft...
This has been a long-standing possible, and then probable, explanation for the anomaly. Seems to have taken quite a bit of effort to figure out what the actual value of the force would be with sufficient precision. I remember what seems like a long time ago an article posted to /. about someone calculating the effect of heat radiation using Phong shading, the 3D graphics technique, as an approximation and got pretty good agreement.
Going all the way to a complete finite element analysis, using multiple methods to come up with the coefficients for the model, and getting a result that leaves only a noise-level signal is pretty impressive. And not what I'd call obvious.
So despite maybe feeling like it, it's not exactly a case of research by the Maximegalon Institute of Slowly and Painfully Working Out the Surprisingly Obvious.
The enemies of Democracy are