[mmaimcal]Re: Comment in ALMA memo 489

[MORITA, Koh-Ichiro]

Dear Mark,

> I suggest that you have an effective algorithm for dealing with the +ACA
> data case, and that you are dealing with the homogeneous array (ALMA+SD)
> case less effectively.  I am calling for a fair comparison.

Do you mean that ALMA+SD mosaic should use OTF scan same
as ACA?  However, the dump rate of the baseline correlator
for cross-correlation is different (much slower) from that
for auto-correlation.  So, I do not know how to realize
an interferometric observation and an OTF single dish scan
simultaneously with the ALMA 64-element array.
Can you give me your detailed idear?

> I suggest two different philosophies for these simulations:
> 
> A)  Make images with the ALMA+SD and ALMA+ACA+SD cases with the
>     exact same data (except for ACA, obviously).    (Presumably,
>     no extra guard band is provided for the ALMA+SD case in this
>     philosophy -- the discussion of the guard band in Memo 489
>     is intended mainly to point out that the extra SD data in
>     the ALMA+ACA+SD case would really have helped the ALMA+SD
>     case).

As I mentioned above, we need to know observing details for
homogeneous mosaics with the 64 element array.

> B)  Ask a different question:  what data is required to make a
>     really good image for the ALMA+SD case?  and for the 
>     ALMA+ACA+SD case?  If we need to spend significantly more
>     time to do one or the other (ie, to get a guard band),
>     we just state those facts.  We don't throw up our hands
>     in advance and say "We'll never get this" -- rather, we
>     look at what extra we might need to get and understand
>     that as a tradeoff -- for example, it might be more
>     efficient to use some extra time with the full ALMA
>     than to use more time with the ACA in some case.  But
>     we can't answer that tradeoff question if we never
>     ask the right questions in the first place.

I fully agreed with you.

Take care,
Koh-Ichiro