Thanks. That gives me a lot to think about.
I can see where precise values for speed and acceleration on a line directly away from the earth can be calculated.
One might use transit time of the signal to get absolute distance from the earth, for example.
I'm less clear on how speed and acceleration can be accurately determined at right angles from the line directly away from the earth.
Does the radio interferometry involve comparing the phase of signals received at different stations widely separated on earth, for example.
Is the determination of position and velocity at right angles to the line directly away from earth basically equivalent to viewing a picture of the sky and determining the apparent position of the craft relative to other objects in the field of view?
I think my difficulty may just stem from the possibility that the Doppler and similar techniques are so precise, that I am expecting similar precision for the apparent position in the sky, when perhaps such precision just isn't necessary to do the job.
I don’t remember this particular aspect when I was reading about this, but I struggle to think of cases in which our crafts travel for any significant amount of time perpendicular to our line of sight to them. By definitition this cannot happen for too long, because either the craft flies straight and we revolve or the craft has arrived and it revolves too. In the frist case the angle will not stay at 90 for too long, in the second case we see it straight on at regular intervals.
For the brief periods the ship might be perpendicular we can use intertial navigation.
The other thing is that I suspect geometry can be used pretty close to 90 deg. Cos(80) is still significantly large at 0.2.