Calibration Attributes of the DRSP

2004/08/26 email from Michiel Hogerheijde announcing calibration attributes report:

As mentioned during last Tuesday's telecon, a report is now available on the calibration attributes of the projects in the Design Reference Science Plan (abstract below).

The report can be found at http://www.strw.leidenuniv.nl/~alma/drsp_calib_report.pdf

The calibration requirements of the individual DRSP projects are at http://www.strw.leidenuniv.nl/~alma/drsp_calib_responses.html

Supporting materials (plots, spreadsheets) can be found at http://www.strw.leidenuniv.nl/~alma/drsp.html

Comments are welcome !

Michiel Hogerheijde

Abstract:

The Design Reference Science Plan offers a valuable opportunity to assess the calibration requirements for the Atacama Large Millimeter Array, as well as the impact that relaxing these requirements will have on the science that can be achieved. This document summarizes the calibration requirements based on 67% of the projects included in the Design Reference Science Plan for which input was received. The majority of projects can be successfully executed with an absolute calibration accuracy of 5%. Stronger requirements are placed on the repeatability and the relative calibration accuracy (both within a single band and between bands), for which most projects require either 1-3% or 5%. The document discusses a number of key arguments that are offered in support of these requirements. Only a few projects in the Design Reference Science Plan include polarization measurements, and no conclusions can be based on their listed requirements of 10 degrees on the angle and 1% on the amplitude.


Comment from Bryan Butler 2004/08/26:

michiel,

nice work. a few comments.

i'm a bit confused by tables 1 & 2 in the writeup. why is there an included "1%" column, when, in fact, there was no such response option in the questionnaire (only "1-3%" was available)? if that were an available selection, there are several of the solar system projects that would have chosen "1%" instead of "1-3%". ditto the "NoRq" column. this wasn't an option, and it appears that you've used the comments rather than strict questionnaire answers to infer that (a similar problem exists in the solar system entries - if that option had been available, it would have been chosen for all of the astrometric projects, whereas it looks like you've only used it for 4.4.2, where the respondents noted in the comments that there was no requirement [this was also noted in my responses for 4.2.7 & 4.4.1]).

i'm also confused by the tabulated responses at http://www.strw.leidenuniv.nl/~alma/drsp_calib_responses.html where many of the solar system responses are repeated (seemingly unneccessarily, at least to me).

let's be a bit careful about this, since it will likely be used by the project to justify loosening the amplitude calibration spec. as you all probably know, i've argued for that for some time (perhaps to my own scientific detriment), but let's be sure it doesn't get loosened by too much. for instance, putting the amplitude calibration spec at 10% (which would, after all, satisfy more than half of the DRSP projects covered in this document, according to table 1) would be a disaster - that's no better (or at least not much better) than OVRO & BIMA do currently (i'm not sure about PdB).

-bryan


...and Michiel's response to Bryan's comments...

Hi Bryan,

I've included 1% because a few responses specifically included that. However, in the interpretation I did not make a distinction between 1% and 1-3%. Many reponses included N/A for various calibration attributes. I felt they should be counted in some way (and not grouped in the 10% box, because that distorts the statistics). Perhaps I shoudl go back and make sure that I have found all cases where 10% was used to mean NoRq.

I have indeed used the provided comments to tally the calibration requirements, trying to be consistent. If you see any inconsistencies, let me know! (That's why I've sent the document around).

As for the duplicated responses: I have counted each DRSP project individually, since they were designed to cover all science topics. If multiple projects have identical requirements, these should still be counted for each occurance (I think).

I agree that we need to be careful about this (hence the posting). I have tried to indicate which science arguments drive the requirements toward high accuracy - perhaps that should be given stronger wording so that - indeed - it is not decided to relax the requirements to 10%...

Michiel


...and Bryan's response to Michiel's response to Bryan's comments...

On 8/26/04 9:28 AM, Michiel Hogerheijde wrote:

'> Hi Bryan,
'>
'> I've included 1% because a few responses specifically included that.
'> However, in the interpretation I did not make a distinction between 1% and
'> 1-3%. Many reponses included N/A for various calibration attributes. I
'> felt they should be counted in some way (and not grouped in the 10% box,
'> because that distorts the statistics). Perhaps I shoudl go back and make
'> sure that I have found all cases where 10% was used to mean NoRq.

well, it still seems to me that we should limit the tabulated results to the answers that were available in the questionnaire. it certainly would have changed the results in the solar system theme - perhaps in others. if somebody replied with an answer that was not one of the provided possible answers, that reply gets rejected - otherwise you get a biased sample. or you can ask the person that sent in the reply to limit it to one of the supplied ones. otherwise we ask everybody if they would have chosen either "1%" or "NoRq" if it had been supplied, and retabulate the results.

'> As for the duplicated responses: I have counted each DRSP project
'> individually, since they were designed to cover all science topics. If
'> multiple projects have identical requirements, these should still be
'> counted for each occurance (I think).

yes, i agree that the accounting has to include them in this way (counting each separate entry), but in the full listing, they can be combined, i think.

-bryan

-- JeffMangum - 07 Sep 2004
Topic revision: r1 - 2004-09-07, JeffMangum
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