[Lamplighter]

300 inches here and 300 inches there...

LA Times
Thomas H. Maugh II
July 18, 2012

Pioneer spacecraft 'anomaly' solved, and it's not new physics

Pioneer 10 and Pioneer 11 were launched in 1972 and 1973, respectively,
on a trajectory toward the edge of the solar system. In the early 1980s,
controllers at NASA's JPL detected a slight deceleration in the crafts' speeds.
The effect was initially dismissed as resulting from leftover propellant in the fuel lines,
but it persisted much longer than could be accounted for by such a cause.
In 1998, John Anderson of JPL and his colleagues calculated that the craft
had a deceleration rate of about 300 inches per day.

Because they had no explanation for the slowing, the team speculated
that it might be caused by some new physics that contradicted
Einstein's general theory of relativity.<snip>

...they were able to calculate the amount of heat generated by the electrical
subsystems of the craft and the decay of plutonium in the power sources.
They concluded that the radiation of that heat in the direction of
the spacecraft's travel was sufficient to explain the slight deceleration.

"The effect is something like when you are driving a car and
the photons from your headlights are pushing you backward," Turyshev said.
"It's very subtle."