[asac] development plan discussion

[KOHNO Kotaro]

Dear Andrew and ASAC members,

Thank you for the discussion in the afternoon session;
on the development plan, I was so stimulated by the discussion
(a f2f meeting is indeed a very good style to stimulate discussion,
as pointed out by Douglas!)
that I built a matrix for clarification.
Note that my basic question during the discussion was why the priority
of the new digital system(including 2nd generation correlator) is so low.

In this matrix, you can easily see what kind of the performance
will be improved by a proposed development item,
although it is very preliminary and incomplete one (so many ?s).

For instance, in order to improve the sensitivity,
you can find 3 development items
(add more antenna, build a new digital system,
and develop a lower noise receiver).
Note that building the new digital system
(including multi-bit digitizer) will immediately
result in a ~10% improvement of sensitivity, which is almost
equivalent to adding 5 more antennas in terms of the improvement of
sensitivity (as pointed out by Morita-san).

Developing a lower noise receiver is another important option
to improve the sensitivity, of course,
but the current ALMA receivers are already achieving extremely low noise.
Frederic kindly pointed out that the receiver development will
widen the band width,
but it may mean that more correlator power must be needed anyway
to process the whole spectral signal from such a wider band receiver.
It could be also true for the case of multi-frequency feed or
multi-beam receivers; they may inevitably need enhanced correlator
power
to process the whole data.

In summary, I agree with that "add a few antenna",
"receiver technology", "multi-beam", and "multi-frequency feeds"
will be indeed high-priority items, but I also feel that the priority of
the new digital system/enhanced correlator system could be
similar to that of these current high-priority items.



Anyway, please take a look of this matrix, and
please correct me if you find any incorrect descriptions.
Unfortunately, I can't attend the tomorrow's meeting, but
I do hope that this matrix could be helpful for the clarification
of this difficult discussion on the prioritization;
such a matrix could be a worth adding
to the final report to the board, I think.


with my best regards,

Kotaro at SCL
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