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). Agenda: - 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? Minutes: - 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