[mmaimcal] Antenna specification question

[Rob Reid]

Hi,

At 2:27 PM EST on November 3 Al Wootten sent:
> Q:  Does the ALMA production antenna have to meet all specifications
> when equipped with a nutator?  If not, the design of the quadripod might
> be optimized for performance without the nutator.

If the demand for total power exceeds what the ACA can provide, it would be
nice to be able to upgrade a few ALMA antennas with nutators.  This is
especially true if OTF mapping with ALMA can't be done fast/stably enough to
get total power, given that the two different types of ALMA antennas might
drive differently.  Admittedly putting nutators on some of the antennas would
probably add to that problem.

> The specifications are unclear on this, but the point of view so far is that
> it must meet all specifications when equipped with a nutator.

I'm new at digging through the ALMA specs, but according to
SCI-90.00.00.00-0230-00, "at least 4 antennas must be equipped with wobbling
subreflectors".  "at least" implies that more might be needed if 4 turns out to
not be enough.  If the production companies are really keen to further split
their designs into nutatored and nutatorless, then presumably they'd need an
agreement on how many nutatored antennas each company is responsible for.

-- 
Rob Reid		A NRAO NAASC ALMA PDF		@   @  @ @  @   @
1-434-244-6822	       	http://www.cv.nrao.edu/~rreid/  ^   ^  ^ ^  ^   ^