[mmaimcal] Re: [Almasci] Two antennas

[John Richer]

Hi Debra,

Yes, the requirements you quote are the ones I was looking at.  I agree
that the intent is somewhat ambiguous as written.  I'm sure someone here
can elaborate.  I did look for the AIPS++ audit that ALMA did to see if
ths shed any light, but I couldn't locate it. 

However I think the intention here is surely to allow different primary
beam responses, given that we are trying to push these dishes up to very
high frequencies where the beam efficiency gets rather modest, and where
beams will necessarily vary from dish to dish no matter which vendor it
came from.

  OL 5.3-R2 Careful (polarized) primary beam correction and pointing 
  correction is critical for high fidelity mosaic imaging and must be 
  incorporated into the mosaicing algorithms.  Priority 1.

     OL-5.3-R2.2 A set of ALMA standard beam images will be made
     available by the project and distributed with the Package, with
     updates available for download when appropriate. Priority: 1

     OL-5.3-R2.3 The user shall be able to specify the primary beam in a
     number of forms, both analytic and tabular, in addition to the ALMA
     provided primary beam. Priority: 2

John


-- 
John Richer      
Astrophysics Group,   Cavendish Lab,   Madingley Road,  Cambridge CB3 0HE
http://www.mrao.cam.ac.uk/~jsr  Tel: +44-1223-337246 Fax: +44-1223-354599  

>>>>> "Debra" == Debra Shepherd <dshepher at aoc.nrao.edu> writes:

    > Hi John,

    > I'm looking through the offline requirements now - there are
    > several that relate to the need to handle the polarized beam
    > response in imaging but none (that I can find) specify that the
    > offline package should be able to handle polarized beam patterns
    > separately for each individual antenna.  The requirements relating
    > to this are:

    > Interferometric imaging section:

    > OL 4.5-R1 Determination of and correction for pointing offsets and
    > the polarized primary beam is critical to the ability to reliably
    > mosaic using ALMA, and this must be available in the Package,
    > preferable in several algorithmic forms.  Priority 1.

    > Mosaic imaging section:

    > OL 5.2-R1 High-fidelity imaging of the entire primary beam in all
    > Stokes parameters is the primary goal - therefore, incorporation
    > of the polarized primary beam response of the array is required.
    > Priority 1.

    > OL 5.3-R2 Careful (polarized) primary beam correction and pointing
    > correction is critical for high fidelity mosaic imaging and must
    > be incorporated intot eh mosaicing algorithms.  Priority 1.


    > I do not find any text that says the beam patterns must be handled
    > separately for each individual antenna.  Perhaps this was the
    > intent but I was not part of the SSR when the requirements were
    > written so I cannot say.  Thus, it appears that it is appropriate
    > to include the increased cost to develop the capability to handle
    > individual polarized beam patterns.

    > Debra


    > On Mon, 7 Nov 2005, John Richer wrote:

    >>  Dear Al,
    >> 
    >> Just a quick note on the article about impact of two antenna
    >> vendors on the Science IPT costs.  It is my understanding (and
    >> someone - maybe Robert Lucas or Christine Wilson - can correct me
    >> if I am wrong) that the software requirements we wrote down in
    >> the SSR several years ago already include the need to handle
    >> (polarised) beam patterns separately for each individual antenna.
    >> I think it is categorised in the offline data processing
    >> requirements at the highest priority.  So I think this work has
    >> already been costed, and cannot be put in here again as an extra
    >> cost.  Whether such capabilites do yet exists within the offline
    >> or pipeline packages, I cannot say.
    >> 
    >> In addition, if there is any extra cost here, it is surely mainly
    >> against software rather than science?
    >> 
    >> Regards
    >> 
    >> John
    >> 
    >> 
    >> 

    > -- 
    > ----
    > -------
    > -----------
    > Debra Shepherd e-mail: dshepher at aoc.nrao.edu National Radio
    > Astronomy Observatory phone: (505) 835-7398 P.O. Box O FAX: (505)
    > 835-7027 Socorro, NM 87801 http://www.nrao.edu/~dshepher