[asac] comments on report

[Tetsuo Hasegawa]

Dear Christine,

At 1:09 PM -0500 01.3.14, Christine Wilson wrote:
> On page 8, maybe I'm just still confused about the correlators, but I have a
> question. Does the reprogramming of the baseline correlator give you the same
> total efficiency as the Future or Enhanced correlator, albeit with many fewer
> channels and some restriction on total bandwidth? If so, it would be nice to
> say so CLEARLY in our report.

My colleagues, i.e., Chikada, Okumura, and Iguchi here in Japan, tell me
that your understanding is correct.

If we sacrifice the number of IF lines by half, we would have a room to
reprogram the baseline correlator to improve the efficiency from 0.88 to
0.98.  In this case, we regain 10% of the sinsitivity PER CHANNEL, but we
lose 50% of the bandwidth.  We can enjoy this 10% gain in a limited case of
spectral line observations over a sacrifice of the continuum sensitivity
and/or opportunity of multiple line mapping.  This is the limit posed by the
absolute amount of the hardware of the baseline correlator, and a
substantial improvement is possible with the enhanced/future correlator.

In revising the corresponding part of the ASAC report, this reservation
should also be stated.

With best,

Tetsuo
_______________________________________________________________
!!! My e-mail address has changed !!!

Tetsuo HASEGAWA, D. Sc.   <tetsuo.hasegawa at nao.ac.jp>
ALMA-J Project Scientist
Professor, National Astronomical Observatory of Japan
2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
Phone +81-422-34-3843 / FAX +81-422-34-3764
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