[mmaimcal] antennas

[Mark Holdaway]

> 
>  As currently practiced, offset pointing is done semi-hourly or so and so
>  can't entirely work against wind buffeting.  I presume that you are considering
>  an offset pointing done on the cal at each cycle of fast switching.  We
> discussed this at the MAC meeting.  Someone--Jack Welch?--suggested that it
> would only take a few seconds to accomplish.  However, this
>  will limit the fast switching duty cycle it seems to me.  We need to model
>  fast switching with pointing included in the cycles, which we have not done.
>  This might take out some pointing jitter on sub-minute time scales.

I think the phase cal sources are generally NOT strong enough for the
pointing cal.  The SNR requirement is greater for pointing, so the sources
will be farther away... and I think you need closer to a minute, including
settle, slew, and five point.  A circular OTF path around the source will
be more efficient, but won't save more than about a factor of 2 in
time.... so I think combining the fast switching phase cal and frequent
pointing cal is not a good idea.

	-Mark