[mmaimcal] Re: antennas & pointing

[Simon Radford]

My dos pesos:

Are the antenna group worried about back reaction of the nutator on the
pointing of the entire telescope or the settling time, etc., of the
nutator when it switches? Both would seem to be issues for the nutator
design. The nutator should be balanced, to avoid back reaction, and
should be driven with optimal waveforems to avoid overshoot, ringing,
etc. In any case, I would not relax the pointing spec for nutation.

I guess most of us are comfortable in relying on frequent offset
pointing to clean up quasi-static problems -- thermal gradients, etc.
This seems a safe extrapolation from current practice. If necessary, we
could push one of the current telescopes to test this -- shuttle between
3c273 and 3c279.

Relying on offset pointing to clean up dynamic problems, i. e., wind,
seems much more risky. I'm not aware of anyone doing this in practice.
I'm not sure we could adequately test this with current telescopes.

Simon