The phenomenon was unknown when the Pioneers and Voyagers were launched
in the 1970s. And as has been repeated elsewhere, the two Voyager probes move
with control jets, negating the ability to look for the anomaly.

While the New Horizons team knew about the Pioneer Anomaly when they launched
their little robot in early 2006, my question is whether they did anything to the
probe to look for the event? I have the feeling the answer is no because their
major objective was to study one large KBO and maybe a few others if the
trajectories worked out and that is about it. The Jupiter system was a bonus,
but I wonder if the Pioneer Anomaly will be so lucky?

When you are one of the few human-made spacecraft in history to leave the
Sol system, one should try to learn as much as we can about a place that
currently takes us decades to reach and has been examined by vehicles with
30-40 year old technology that were not meant to be working tha far out.

C'mon Innovative Interstellar Explorer!

http://interstellarexplorer.jhuapl.edu/