Calibration Group Phone Telecon Meeting Minutes  -  2002Aug27

Attending: Butler, Carter, D'Addario, Gueth, Holdaway, Isaak, Lucas, 
  Mangum, Morita, Myers, Pardo, Radford, Richer, Woody, Wootten, Wright
  (apologies to anybody I missed, the phone wasn't beeping when people
   were connected, so there may have been several that I missed).


 - discussion of memo review process and reviews already received
 - discussion of possibility of making a new specs document
 - things to do and timeline
 - interaction of our group with others (ATF, SSR, etc...)
 - next phone meeting and frequency?
 - next face-to-face meeting?


 - Lively discussion on the memo review process substance and 
   mechanics.  Richer pointed out that the process and its goals
   should be reviewed, which Butler + Wootten did.  Butler pointed
   out that goal (of both the group as a whole and specifically of
   this memo review process) is to produce 2 documents - first, a 
   new set of specifications which related directly to calibration; 
   second, a description of how we expect to meet these 
   specifications (which is how they trickle down to instrumental 
   specs, and would naturally incorporate a specific plan for 
   calibration of all necessary quantities).  D'Addario pointed out 
   the difference between live and static (archived) documents - e.g., 
   specifications are live; memos are static.  He also pointed out that 
   specifications must be submitted to the project office and will go 
   through their own review process (after which it can be declared a 
   'project level document').  Woody pointed out that guidelines for 
   reviewers did not contain specific instructions to review the memo 
   with the idea of stamping it as 'approved', so he reviewed his memos
   with an eye toward scientific correctness, not whether they
   should be adopted as policy by the project.  All who voiced an 
   opinion thought that the idea should /not/ be to stamp individual
   memos as 'approved' by the project, but rather to take those parts
   which survive the memo review process and incorporate them into
   one of the two documents which we are working toward.

 - Discussion then turned to specific memo reviews, concentrating on
   those memos which impact either the amplitude calibration devices
   (dual-load or semi-transparent vane) or the photonic source (because
   those are the ones under budgetary pressure currently).  D'Addario
   pointed out that the discussion to this point has been extremely 
   vague and muddled about exactly /what/ is being calibrated by these
   devices.  For instance, the distinction between calibrating the 
   atmosphere vs. the instrument has been confused, and the distinction
   between single dish and interferometric calibration has also been
   confused.  Myers echoed this sentiment at a later time (specifically
   with reference to memo 423).  Woody described what is done currently 
   at mm arrays, which is essentially what we are trying to do, but 
   much more accurately.  Butler pointed out that we can't do this in 
   the way that we do it in the cm, where we look at sources of 'known'
   flux density, because we don't know any sources to 1% accuracy.  
   In discussion on the semi-transparent vane device, Woody pointed out 
   that it might be OK to operate in saturation (this is an issue for 
   the 'hot' load part of that system).  There was discussion on this, 
   but it seems to be an open question - it is not clear that operating 
   in saturation will be a problem (especially given that the SIS 
   devices are multi-junction), but it /might/ be.  We just do not know 
   enough about it at this point to make a conclusion.  Woody also 
   pointed out that the right way to do it was with 4 loads (cold [sky],
   ambient, hot, and semi-transparent vane), which Mangum has apparently
   written a draft memo on (and is in Plambeck's memo 321?).  Richer 
   pointed out that we should perhaps make an official recommendation as
   a group to management as to what to do in this area.  Wootten pointed
   out (and this was echoed by Butler and Wright at least) that the 
   right recommendation was to continue study of both systems, since we 
   have no working version of either (although Carter pointed out that 
   the design for the semi-transparent vane device was nearly final). 
   There was discussion of testing this on the 'prototype 
   interferometer' (/if/ that happens).  Richer pointed out that there 
   was an official AO on the European side for the construction of the 
   semi-transparent vane device.  Wootten pointed out that this 
   illustrates a fundamental difference between the funding and 
   planning for the 2 devices, since no such formal level of support 
   is given to the dual-load device (there is a work package for its
   construction, but none for design/testing).  Wootten will pursue 
   getting the dual-load device added to the project in a more complete 
   way than it is currently.

   Discussion on the photonic device centered mostly on problems 
   related to it.  It will be difficult to control the power output
   as a function of frequency to the required level, meaning that it
   might not be useful for amplitude/bandpass calibration.  It should
   still be useful for polarization however.  D'Addario pointed out
   that it is the only proposed calibration device which is coherent
   and as such still might be very useful.  Woody (and others) pointed
   out that part of the problem is that the device is poorly defined, 
   with only a paragraph or so in a memo by John Payne (which I can't
   find with a cursory examination of memos 396 and 297).  Wootten 
   pointed out that Guilloteau and Aurore Bacmann (at ESO) are working
   on a document which might help with the description of the bandpass 
   capabilities of this device (although it is uncertain exactly what
   work is being done by Guilloteau and Bacmann on this, and it might
   be a much more generic bandpass calibration description rather than
   focusing on this device - we are supposed to have a presentation on
   this at the ASAC meeting).

 - Discussion then turned to timeline.  Wootten pointed out that the 
   deadlines are determined by the project milestones, which are few
   and far between.  It appears that the driving milestones for us are
   the operation of the prototype interferometer (which is not an 
   official project milestone, but is scheduled for 'after Jan 1 2004'),
   the initial FE system available at the OSF (Q4 2005), and start of
   early science operations (Q3 2007).  Richer pointed out that a more 
   coherent description of the charge to our group would help us to 
   understand what we should be doing, and Butler agreed to attempt to
   modify the initial announcement of the creation of this group from
   Guilloteau and Wootten to that end.  A problem is that we are 
   often not aware of budgetary decisions and dates, which our work
   might have an influence on, or vice versa.

 - Butler proposed to have a telecon next month, since we will likely
   have material brought up at the ASAC meeting (sep6-8) to discuss.
   Subsequent meetings might occur monthly, or as needed.

 - Butler proposed that a face-to-face meeting might be appropriate 
   next spring, but venue, date, and length are uncertain, so further
   input on this issue was solicited from the group (it was noted that
   this might be arranged to coincide with ALMA week, if one occurs
   next spring).

dutifully scribed by bjb.  2002Aug27-28