[asac]charge 3

[Chris Carilli]

Attached is email exchange concerning charge 3,
plus Hogerheidje document, as start to our deliberations.
cc



Chris Carilli wrote:

> Sept 1, 2004
>
> to: A. Wootten, M. Holdaway, J. Mangum
> from: C. Carilli
> re: Charge 3 - alma calibration
> cc: P. Cox
>
> Al, Mark,
>
> Pierre Cox and I have been asked to look after charge 3 from the ALMA
> board for the ISAC (august 5 charges).  The charge states:
>
> "Help the science IPT plan their study of the impact of calibration on
> a handful of the most challenging major science goals, in particular
> by providing the ASAC's views on the types of projects you feel are
> the most challenging from a calibration point of view.  Review and
> comment on the science IPT report when finished."
>
> Have you'all started any such effort?  In the ASAC report from June we
> had a short section on calibration demands, and a few examples expanded
> from the DRSP:
>
> Carilli - high z star forming galaxy SEDs and T_dust -- ALMA memo 492
> Dutrey - protoplanetary disks and dust absorption coefficeint (beta)
> Bacmann - density and temp profile in pre-stellar cores
>
> None of these was particularly demanding, typically at the 3% to 10%
> level.
>
> Pierre and I will comb the DRSP, and perhaps previous ALMA science
> documents, for high profile science projects that are very demanding
> on the calibration. Also, Hogerheidje has a distillation of the DRSP
> with amplitude calibration requirements (attached).  We can hijack that
> as well. 
> Possible calibration issues we might consider: phase, amplitude
> (relative, absolute), polarization, bandpass.  Unclear what the board
> had in mind, except my impression was that they really wanted
> us to focus on the 1% calibration bugga-boo?
>
> Guidance on how to proceed, and an up-date on what the IPT is doing,
> would be most appreciated.  The ISAC telecon is Sept. 9, and the ISAC
> meeting is Sept 28. Having something to discuss prior to Sept 28 would
> be a good thing.
>
> thanks,
> cc
>
>

Al Wootten wrote:

>Hi Chris
>
>1) Science IPT activities:
>We've discussed the summary from Hogerheijde of calibration needs for the 
>DRSP at the Science IPT meeting last week and very briefly (I think no one
>had read the document from Michiel) at the ImCal meeting last Tuesday.  
>That is, of course, the product of the Science IPT.
>
>I am at the moment going through that to distill what I think are
>critical goals.  I read the charge as focusing directly
>on the top level science goals spelled out in the Project Plan and in
>the Science Requirements, augmented by the projects in the DRSP (we specifically
>populated the DRSP with the major science goals from the preceding science
>documents). 
>
>I intend to use these studies to guide the revision to the calibration
>specifications and requirements document currently scheduled to be
>considered for adoption by the project by the change control board on
>10 September.  I plan to have a new draft of that document ready tomorrow,
>if the petty bureaucratic shackles with which we have recently been bound
>aren't tightened so much that I can't accomplish that (several reports to
>management a week recently).
>
>2) Project Directives
>Massimo has already told the Board (Ewine, John Richer and I were present)
>last 3 November that he will not accept a document based on the 
>blanket 1%/3% as is in the current document.  He told the Board that 
>he believed a 5% goal was appropriate.  As Director, he bases this on
>cost and schedule as much as what he believes the science requires.
>In the minutes of that meeting, the Board scribe wrote that as 5% in
>stability and John Richer, Ewine and I were unable to get that changed in
>the minutes.  The written record shows no guidance from project leadership
>or from the Board on calibration.  In my talk to at ALMA Week and at the
>ASAC meeting in May I proposed doing that.  When the Cal Specs and Reqs came
>before the CCB in March Massimo directed me to revise the document to
>reflect a calibration goal which we can demonstrate is achievable and which
>we can demonstrate is necessary for the scientific goals of ALMA.
>Currently, I think the Science IPT would agree that we cannot demonstrate that
>1% amplitude calibration is achievable.  I think we can demonstrate that
>3% is achievable at the lower frequencies and at least make a convincing case
>that 5% is achievable at the higher frequencies.
>
>It seems to me at this point, from Hogerheijde's studies,
>Butler's studies and my own study, that we should focus on 5% absolute
>calibration and relative calibration accuracy of 3%/5%.   It is clear to me
>that the project leadership believes that the cost of trying to achieve
>1% is too great.  One could argue that 10% absolute calibration accuracy is
>sufficient for most projects.  Personally, I don't think that is sufficiently
>forward thinking.
>
>3) Science IPT plans
>Right now the Board is reconsidering a rewrite of the Project Plan.  The
>Science Requirements document is written from the point of view of PP v1.0.
>That has not been adopted but the current version does have comments I've
>received (I'm sure Beasley will demand more revisions when he arrives) 
>addressed.  Below this are the system technical specs, recently approved by
>the CCB and the calibration specs and reqs.  Below that is the calibration
>plan, which demonstrates how the cal specs and reqs will be met.  Most of
>the 'demonstration' is in documents in the memo series which, as you know,
>are externally reviewed before becoming part of the plan.  The next version
>of the Calibration Plan is due 1 Oct, but the current version is pretty
>complete, I believe.  An element which is missing is the examples, which
>will be based on the DRSP and the survey of calibration needs of its projects.
>If you and Pierre and the ASAC would like to suggest some particularly 
>challenging projects, I think examples of challenging projects would be
>useful for the CP.
>
>4) ASAC
>I proposed a strawman agenda to the ASAC leadership on 13 August but I have
>had no comment whatsoever from them on it.  I'm glad you and Pierre are
>actively pursuing this charge--perhaps you should cc Schilke and Turner.
>I've just been summoned to court on 28 Sept so I'll miss that morning at
>least.  BTW there is a link to the strawman agenda on the 31 August
>agenda of the Imaging and Calibration group--or get it directly from:
>http://www.cv.nrao.edu/~awootten/asaccvilleagendav0.50.html
>Comments would be appreciated.
>
>Cieux clairs,
>Al
>+--------------------------------------------------------+
>| Alwyn  Wootten   (http://www.cv.nrao.edu/~awootten/)	 |
>| Project Scientist, Atacama Large Millimeter Array/US   |
>| Astronomer, National Radio Astronomy Observatory       |        
>| 520 Edgemont Road, Charlottesville, VA 22903-2475, USA |
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>



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