In five of the six flybys, the scientists have confirmed anomalies.
"I am feeling both humble and perplexed by this," said Anderson, who is now working as a retiree. "There is something very strange going on with spacecraft motions. We have no convincing explanation for either the Pioneer anomaly or the flyby anomaly."
For some time, the Pioneer probes hurtling out of our solar system seem to be slowing down without explanation. Now it seems that some other probes, when flying by the earth, seem to be going faster: