Philip Witham, <email@example.com>, writes, regarding the anomalous
> I any event, could it simply be that the distribution of dust/dark
> matter/gas molecules in the vicinity of the sun and particularly in the
> plane of the ecliptic is significantly different than believed? Perhaps
> the total estimated density of dark matter is correct, but it is not
> distributed as expected. I thinking of drag on the probe. Is Pioneer 10
> in the plane of the ecliptic?
I don't believe the Pioneer craft are near the plane of the ecliptic.
The drag hypothesis was considered and rejected by looking at data on the Ulysses probe, which was travelling at a different speed and direction. It, too, saw a radial acceleration towards the sun of about the same magnitude as the Pioneer craft. However it did sound like the effect was more ambiguous here, as the solar wind was much stronger and so more correction factors were needed.