Jonathan Silverlight wrote in message ...
I haven't seen any evidence of an anomaly on Cassini.

Presumably the reason Cassini hasn't seen an acceleration is that it's
more than 20 x as massive.

Let's be clear he the Cassini spacecraft shows a LARGER
non-gravitational acceleration than the Pioneer's. But since it
was designed to radiate RTG waste heat primarily out the back, this
is not considered to be anomalous.

Spacecraft Mass Acceleration P(rtg) mac/P
Cassini 5200 kg -3E-9 m/s^2 10000 W 50%
Pioneer 258 kg -8E-10 m/s^2 2000 W 3%

F = ma is the force, and Fc = mac is the power needed to
give this force in a photon rocket. Cassini is radiating
its wast heat with a 50% asymmetry factor, while Pioneer only needs
to be 3% asymmetric to explain its "anomalous" acceleration.

Note that asteroids also show a non-gravitational acceleration due
to the asymmetric radiation of absorbed sunlight. This is called
the Yarkovsky effect. So there is no particular reason to require
new physics to explain the behavior of the Pioneers.

--Edward L. (Ned) Wright, UCLA Professor of Physics and Astronomy
See http:www.astro.ucla.edu/~wright/cosmolog.htm