Calibration Group Phone Telecon Meeting Minutes  -  2003May08

Attending: Bacmann, Butler, Hasegawa, Hills, Isaak, Martin-Pintado,
   Richer, Wilson, Wootten, Wright
   (apologies to anybody I missed - Al had already initiated the
   telecon when I got connected, and there were a few 
   connects/disconnects during the telecon).



 - Richard summarized the document he and John produced as the (somewhat
   final) draft on the required ancillary calibration devices.  The
   main remaining questions are what work remains to be done, and just
   who will do that work?  The Science IPT and Cal Group together need
   to decide what needs to be done, but it is still unclear who is to
   do that work.  It will be tied in detail to the atmospheric modelling
   work.  Richard, in his WVR workpackage proposal, has money for 
   a student, who *might* be able to do part of this work, but that
   workpackage is not approved yet, so we cannot rely on that.  Juan 
   could possibly do some of the work, but it must be coordinated and 
   well defined.

 - Bryan pointed out that the ATM software was nearing availability.
   Juan has sent the bits of the code and it should be available on the
   web site soon.

 - Jesus summarized the new results on the S/T vane testing at the 30-m
   telescope.  They are much more encouraging than the previous results.
   The main difference was that the vane was moved further from the 
   feed.  It was also thicker (4 cm), and a new material was tested in
   addition to the one that had been used previously.  The peak-to-peak
   variation (varies with frequency and with day) is about 2%.  The 
   systematics are still not understood completely - there are changes 
   with time at 3mm, and differences between the two receivers.  Jesus 
   thinks that the S/T vane system *might* get us to 2% accuracy, but 
   it will be extremely difficult to get better than that.  Butler 
   inquired as to whether the vane filled the beam entirely.  Jesus 
   answered that it did.  Richard asked whether more measurements were 
   planned, to which Jesus replied that they were, but it remains 
   difficult to get time on the telescope.  There will be more tests in 
   roughly one month (a couple of days), but summer is coming, and the 
   tests will not continue beyond that.  They would especially like to 
   measure the variation as a function of elevation.  Jesus pointed out 
   that the measurement of the vane losses to the required accuracy is 
   very difficult.

 - Butler summarized ALMA week activities.  There was extended 
   discussion on the WVR session.  This session is still quite unsettled
   and there were several suggested changes to the agenda.  Tetsuo 
   suggested that we have a summary of other phase error sources.  
   Somebody (sorry, I don't have this in my notes!) noted that the 
   Richer+Hills review should go before the SE/FE section.  Butler noted
   that we might want a status report on the current status at other 
   observatories.  Wright pointed out that Dick Plambeck is the right 
   person for such a summary at BIMA.  Dave Woody is the obvious
   candidate for OVRO and/or CARMA.  There was little discussion of 
   the calibration session agenda - most thought it was fairly 
   reasonable.  Tetsuo recommended that we add a short discussion of 
   ACA issues.

 - Butler proposed the idea of a face-to-face meeting of the Cal Group
   late next fall or early in the winter.  This would be a good time, 
   as ATF results should be in hand, it will be after the calibration 
   plan document deadline, and the situation with the Japanese should 
   be cleared up.  Butler will look into dates & locations.

dutifully scribed by bjb on 2003May08, electronically transcribed 2003May22.