[grey_whiskers]

This bending causes the probe to acquire a momentum component that is transverse to its direction of travel, but because its total momentum is roughly constant, its momentum along our line of sight (which is what the Doppler shift measures) is necessarily reduced.

It'd take an accelerator jock to think of this. Kind of reminds me of GC/Mass Spec. Can we check the estimate of the charge by looking at curvature of the flight path, the mass, and the applied B field? (Wink, nudge)

[Physicist]

Can we check the estimate of the charge by looking at curvature of the flight path, the mass, and the applied B field?

I don't know whether we have a good estimate of the magnetic field out there. If my explanation is correct, it may turn out that it was rejected early on because of mistaken assumptions about the size of the magnetic field and the net charge on the probes.