Since you're so interested in the Pioneer Anomaly, Alex, here's a recent article which will (or should, if they're correct) put the matter to rest once and for all....
http://www.technologyreview.com/blog/arxiv/27012/
Seems they've found the Sunward acceleration of the Pioneer probes is decreasing at an exponential rate. Squarely in line with the radioactive decay of the Po238 powered generators on the spacecraft's generator boom.
http://arxiv.org/abs/1107.2886
It appears to be confirmation of an earlier study by European physicists
http://www.technologyreview.com/blog/arxiv/26589/
http://arxiv.org/abs/1103.5222