Craig Markwardt wrote in message ...
(Nodem Info. Sys.) writes:

I believe that there is a discrepancy between the time-delay and
Doppler ranging measurements. The modeled acceleration can be
measured from the time-delay, however, the Pioneer anomaly will only
show up on the Doppler ranging (in addition to the modeled
acceleration). If the anomaly was due to a real change in velocity,
then both measurement methods would give the same result.

You are incorrect. All the measurement methods are the same, i.e.,
Cassini and the other spacecraft mentioned in this thread *all* use
Doppler tracking. The published paper in Nature does *not* use
"time-delay" (ranging). There is no such thing as "Doppler ranging,"
since Doppler tracking and ranging are quite independent techniques.

It is likely that any conclusions drawn from your incorrect premises
are thus irrelevant.

CM

Sorry about using the wrong terminology, I guess I confused you a bit
there.

Let me clarify things he

According to the Nature article you mention, there is a 'modeled'
acceleration considered to be due entirely to the non-isotropic
radiation from the RTGs. The article states this as around 30 x 10^-8
cm/s^2, which is almost 4 times the Pioneer anomaly (the sign is the
same for both). According to the article, "Deriving this acceleration
from a model of the spacecraft is a difficult task". Therefore it
must be measured, and then the measurement is *assumed* to relate to
*known* parameters such as the radiation from RTGs.

So what we have is something that contains the Pioneer anomaly, but
because it is labeled as 'modeled'... poof!.. the 'unmodeled' Pioneer
anomaly is not there. Now that's a great bit of science!

The time-delay *ranging* measurements (assume we will make a series of
them over a period of time) can be used to measure the velocity of the
probe, and the change in velocity of the probe (acceleration). This
acceleration can be used to gain a true measurement of what is
considered as the 'modeled' acceleration (this would come out around
19 x 10^-8 cm/s^2).

The Doppler *tracking* measurements will contain an additional effect
caused by the curvature of space time, resulting in an additional
apparent acceleration of 8.143 x 10^-8 cm/s^2 towards the observer.
The combined 'modeled' and 'Pioneer anomaly' acceleration would add up
to around the 27 x 10^-8 cm/s^2 figure quoted in the article.

So how did that article show there was no Pioneer anomaly?