[asac] ASAC Meeting

[Stephane Guilloteau]

Following Dr.Nakai E-Mail, I would like to raise the following points

- Number of antennas:  78 is 64xsqrt(3/2), which means that by sharing with
3 equal partners, each partner
    get the same sensitivity than sharing 64 antennas with 2 partners only.
Each scientist thus sees no reduction,
   but we do more science

- Number of small antennas; It is yet unclear that 7 antennas would be
sufficient. I have been (slowly) working
    on that and consider that they make an appropriate match  IF AND ONLY IF
        1) the large antennas make mosaicing 25 % of the time
        2) the small antennas observe in a compact array mode all the time
        3) calibration is not considered as a limitation
    The two statements are somewhat contradictory since 3) would require a
tied array mode for calibration
    while because of 1) and 2) the large and small antennas would be mostly
doing different things (75 %
    of the time).
        Imaging issues are unclear also (is 7 antennas sufficient ?)

    If not, a number like 15 antennas preserve a better imaging capability,
perhaps enough calibration accuracy
    even in stand-alone mode (no hybrid baselines). This is a "Safe Fall
Back"

    Question:
        Does ASAC recommand to "sacrifice" a few large antennas (8) in order
to be able to have more smaller ones.
        Final numbers could be        Large antennas 70,  Small antennas 15.

 - Receivers and LO
    I consider both for scientific and calibration reasons the 2-mm band to
be essential (high redshift objects, see
    my contribution to the Washington meeting). Any comment from ASAC ?

 - Backend
    Does the correlator cost includes the cost of the required computing
system to process the 125 kChannels per
    baseline ?
    If not, what would you estimate this cost to be ?


        Stephane