ALMA Science Advisory Committee
Draft Minutes for ASAC Telecon November 13, 2000
Conference Date: November 013-2000 (Monday)
Participants: G. Blake, L. Bronfman, Y. Chikada, P. Cox, D. Emerson, S.
Guilloteau, M. Gurwell, N. Nakai, M. Rafal, J. Richer, N. Scoville, P. Shaver,
E. van Dishoeck, M. Walmsley, W. Welch, A. Wootten, S. Yamamoto
1. Minutes of last Teleconference
The minutes of the last teleconference were accepted, subject to a few
revisions.
2. Report on ACC Meeting
S. Guilloteau gave a summary of the October meeting of the ACC. The most
important development was a formal statement of interest from Japan in
joining as a third equal partner. The goal is to complete the definition
of a 3-way project by the fall of 2001. M. Rafal said that the ACC had
given guidelines to the AEC in which savings of at least 10% per partner
should be realized relative to the current two-way project.
J. Welch asked about the implications for the ASAC. Full Japanese
participation in the ASAC is now planned, and the Japanese members will
be announced at the next ASAC teleconference.
3. Extension of Band 3 to Lower Frequencies
L. D’Addario’s note on the proposed extension of band 3 to lower
frequencies was discussed, although it was felt that comments from the
receiver group were also needed before final conclusions were reached.
There was general agreement that an extension to 86 GHz is important,
particularly to access the J=1-0 SiO line and the J=1-0 lines of
HCN, HCO+ and their isotopes, and extension to even lower
frequencies is desirable. On the other hand, provision of band 2 becomes
more likely with Japanese participation. It was agreed that, while there
should be no compromise on the performance in the 89-116 GHz range, the
possibility of extending to lower frequencies
should be pursued. The ASAC would like to receive from the
JDRG an estimate of the degradation in performance below 89 GHz if
Band 3 were extended down to 86 GHz, 84 GHz and even as far down as 80
GHz.
4. Scientific Merit of the Enhanced Correlator
Concerning the memo from T. Hasegawa, N. Nakai, and S. Yamamoto, N.
Scoville and S. Guilloteau commented that the European and Japanese
plans for an enhanced correlator are converging towards similar specs,
although both are concerned about the implied data rate. It is important
to pursue the technical development studies before making final
decisions. S. Guilloteau said that the enhanced correlator, particularly
3-bit, could bring a major efficiency gain relative to the investment,
provided it has no sensitivity loss for the “normal” science cases. It
was agreed, in line with the proposal from Hasegawa, Nakai and Yamamoto,
that the ASAC should discuss the scientific merit of the enhanced
correlator regardless of its technical implementation, along with some
science examples. This will be done at the Florence face-to-face
meeting based on documents written by the correlator
teams prior to the meeting.
S. Guilloteau also commented that the compact array should work as a
stand-alone array, and thus can be accommodated by the baseline
correlator. Also, there should be no trade-off in which the number of
12m antennas is reduced below 64, as at least this number of antennas is
required for good imaging quality.
5. Site
A. Wootten reported on a meeting that took place on Monday 7 November in
Charlottesville with A. Readhead and others to discuss the Caltech
experience on the site. Overall the weather had been excellent, giving
one hundred times more efficiency than at Owens Valley. However 10% of
the time had been problematic, with snow and sometimes liquid water in
the atmosphere. Wind was not a real problem, and appropriate site
development and engineering can alleviate the problems due to snow. A.
Readhead suggested that additional relevant specs be made for the
antennas. There is a plan to correlate the CBI results with the 225 GHz
tipper 'stare mode' results. The 183 GHz radiometer also 'stares' and
data from either of these should result in a measurement in total power
fluctuations which may be compared to CBI measurements, especially at
times when liquid water appears to be present.
A memo on this meeting has been prepared. A. Wootten also
reported that comparative contemporaneous
studies for corresponding time periods have
now been made for Chajnantor vs. Pampa la Bola: Radford's preliminary
result is that during 1999 June - December
tranparency was 15-30% better over Chajnantor than over Pampa la Bola.
Butler finds
that the median phase fluctuations at Chajnantor are ~12% better than
at Pampa la Bola, averaged over all times. During the lowest rms phase
fluctuations, Pampa la Bola fluctuations are 43% worse than at Chajnantor.
6. AOB
A. Wootten announced that both the NSF and the NRC have now signed the
agreement for Canada’s participation in the project. Canada’s share will
be 10% of the North American side of the project.
7. Next Meetings
The next face-to-face meeting of the ASAC is now confirmed to take place
in Florence on 23-24 February. About 35 participants are expected. All
are asked to e-mail M. Walmsley indicating their likely participation as
soon as possible.
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Dear Interested Participants in the ASAC Face-to-face meeting,
This concerns those interested in attending the Florence
face-to-face meeting of the ALMA ASAC on Feb 23-24. We have
reserved for this meeting the "Sala Bargello" of the "Convitto
della Calza" , Piazza della Calza 6, close to the Porta Romana
on the south-western corner of the Florence city walls. This
is within walking distance of the Florence city center and all
the tourist attractions.
We have had some problems organising hotel rooms for the meeting.
We first thought that the rooms within the Convitto itself would
be available and that turned out eventually not to be the case.
We have therefore made a pre--reservation of blocks of rooms in
two neighbouring hotels : the "Hotel Classic" on Viale Machiavelli
and the Pensione Annalena on Via Romana. The charges per night
are of the order US$ 100 for the Hotel Classic and $125 for the
Pensione Annalena. We need to know fairly soon how many people
intend to come and therefore request you to send us a statement of
intent using the "form" attatched below. We want this preliminary
information prior to Dec. 15 . Those who send us this information
will be assigned a hotel and requested to contact the hotels directly
by Fax sending credit card information etc. Those who do not reply
are warned that they will be subject to the wild and wooly struggle
with the Florence hotel booking system. This can be fun but we
leave it to you.
Please complete the ASAC response form and return it as
indicated.
The next ASAC teleconference is scheduled for Monday 11th December at 1515 UT.