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 your email to "mmaimcal" (until about 2:00 AM Friday morning, those at other sites will have to use "mmaimcal@majordomo.cv.nrao.edu" as the mail alias table for each site does not know about this new address. Any time you "reply" to a message it will go to the group rather than just the sender.