[mmaimcal] Meeting Tues 1 Sept, exploder, and other news

[Al Wootten]

Folks

Several of us will not be available Monday, so I propose to have our
meeting at the time used previously for site discussions on Tuesday.

So let's enjoy a phone meeting
TUESDAY, 1 September, at 4pm EDT.  The CV SoundStation
Premier Conference phone is at:
(804)296-7082

Agenda

1) Bock sent a report on 11.3.2.1 which I forwarded to Jeff.  He may
discuss that.  The WBS is accepted folks.  Next, dictionary descriptions
of the items in it to the second level of depth.

2) 183 GHz.  We started on this last week; let's continue discussion.
Simon: Chilean 183 GHz radiometers, cloud estimates, radiosondes and
other site testing activities and plans.  

Bryan:  Wiedner thesis, if he has had time to go over it.  At least, we
should all know of its availability.

All: Jack's paper, and his worries about use of 183 GHz rather than 22 GHz.
Bryan, Min and Darrel at least, have copies of this paper, though mine was
missing Figures 7,8,9.

This item leads to a plan for a recommendation on 22/183 GHz for phase
correction radiometers.  Jack feels that useful long wavelength (3mm and
longer) might be done with light cloud cover, but that those clouds might
be sufficiently aborbing at 183 GHz that a radiometer there will not detect all
of the water vapor above it.  A 22 GHz radiometer may be able to detect all
of the vapor, and allow good phase corrections to be made.

We need to address the severity of the problem at Chajnantor, and to provide
a plan for solving it.  The camera on site provides horizon images, which
have provided some daytime statistics for cloud cover.  A fisheye camera
might give better overall statistics; an infrared camera could provide complete
diurnal coverage.  For each day we also have 225 GHz tipper opacities, and
phase measurements with the interferometer.  Comparison of these datasets
should allow us to estimate the percentage of the time for which the cloud
cover contained significant amounts of water, what those amounts were
(tranferrable to 183 GHz initially through atmospheric models, eventually
via direct measurement), and their effect on phase correction.  Thus we could
know whether the clouds' opacity hid a significant amount of water vapor.
Radiosonde data will eventually provide a direct probe of the clouds for
some time intervals.

Existing measurements verify atmospheric modeling in that during two
six minute runs at the JCMT-CSO interferometer, one occurring during
1mm PWV conditions and one during 4mm PWV conditions, the line center
emission could be measured during the former, but not during the latter
period.  As a rough guide, Fig 5. of the site selection report suggests
that 1mm PWV occurs about 40% of the time; 4mm PWV or worse less than
10% of the time.  I estimate that Jack's concerns might be met about
20% of the time, very roughly.  It might be possible to improve that with
clever siting of sampling bands for the 183 GHz line, at the cost of
additional complexity.

3) Brochure.  Juan just revised the old multipage brochure into an uptodate
Spanish version.  He will also revise the Chilean and American versions,
bringing them up to date and parallel to each other.

4) Exploder.   Jeff and Rob have set up an exploder for our discussions.
I used it for this message.  To send to the list, just address
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