Perhaps I should have added some emphasis, the relevant
part wasn't the uncertainty in magnitude but the statement
regarding the direction. You said "They don't give any precise
vector" but they do in fact say that the direction is within
the beamwidth, or +/- 1.8 degrees of the line from the craft
to the Sun. Think of what you were suggesting:


ecliptic: ----P----------E--S---------

The dashes show the plane, P is Pioneer, E is Earth and
S is the Sun. Your putative extra star would be somewhere
off in this direction:

|
|
V

but the anomalous acceleration is in the plane to within
2 degrees.

As soon as the vodka from the past few days wears off I'll try to give
that paper another look. But this is a good discussion.





What is the angular acceleration of a planet, say Earth. Not to
mention its instantaneous linear tangential velocity. IT'S HUGE.

Both very small, if the Earth were in a circular orbit
both would be exactly zero. The _radial_ acceleration
is larger, but why don't you calculate it as a simple
excercise to get a feel for the numbers.

I'm surprised no one nailed me on that gaff. Yeah I was about to try
running those numbers before my time ran out. I'm using a limited use
public computer. Hey Google, how about a spell checker for the news
groups.




Take that vector and add it to ~ 8*10^ -8 (that's a minus 8) cm/s^2
and you basically get that vector. I don't know if we could even
measure such a small change over many years.

Easily.

Are just the tidal forces enough to mask such a small quantity?