[mmaimcal] Q-band on ALMA

[Steven T. Myers]

> The phase stability will usually be the limiting factor, even with fast
> switching or radiometric phase calibration (David Woody gave me an
> optimistic equation to estimate residual phase errors in the radiometric
> case).  And yes, there is plenty of time when the array is unuable at 3mm.  
> I don't have the numbers in front of me, but I recall its like 5% totally
> unusable, 10% usable only at Q band, etc.

Indeed, I made this case to Stephane, but he insisted that this was not
the case and 86 GHz would be useable essentially all of the time, claiming
that this is what the found at IRAM.  We will need to carefully document
this - probably should base it on the data from Devlin's MAT experiment
(which observed at Ka/Q/W bands) as well as the site testing info.

The other points about point source sensitivity (I had those numbers in
the poster) and surface brightness sensitivity (this might be critical
since it is not unlikely that the E array for VLA++ will be descoped).

Also, is anyone else even a little concerned about putting all the
receivers in a single (4K) dewar?  It might be good to have a second
15 K dewar with 30-45 GHz band and maybe the 86+ GHz band also.  This
would ameliorate some of the percieved extra costs associated with
the Ka/Q band stuff.

By the way, the project book has 67 - 90 GHz and 89 - 116 GHz bands,
in which case the 67 - 90 is a likely candidate for HFET/MMIC tech.
Is this still in the plan, or like the rest of the project book is
this horribly out of date?

It is likely that several documents in support of the low bands will
need to be prepared.  Keep thinking about this...

  -steve