Conference Date: April 12-2001 (Thurssday)
Here's the dial-in information for the telecon:
Conference Date: 12 Apr 2001
Conference Time: 10:15 AM EASTERN TIME=14:15 UT
Conference Duration: 1 hr
Service Level: STANDARD
Call Type: MEET ME/DIALOUT
USA Toll Free Number: 888-791-2132
Non-USA Number: +1-415-228-4574
PASSCODE: ALMA
Conference Leader: Mr Al Wootten
Agenda items so far include:
Old Business
(1) Please approve the minutes of the March Meeting.
New Business
(1) - ACC Meeting in Tokyo; Formation of Expanded ACC
(Guilloteau)
A resolution was signed by
Dr. Cesarsky, Chair of the ACC, Dr. Eisenstein, Vice Chair of the ACC and
Dr. Kaifu, Director-General of NAO-J, concerning the Partnership for planning
the Atacama Large Millimeter/Submillimeter Array (ALMA). One aspect
of this resolution was that a Japanese Delegation will, with immediate
effect, participate in the work of the ACC through an expanded ALMA Coordinating
Committee. Members of this expanded ACC for Japan were announced
as M. Shibata (MEXT), T. Godai (Director, Japanese Space Commission), H.
Okuda (ISAS), Y. Tanaka (Board of Councilors, NAO-J), N. Kaifu (Director-General
of NAO-J), S. Ikeuchi (Science Council of Japan) and Kodaira (President,
General Research University). Please see the
press release.
(2) - Next Face-toFace Meeting ( L. Bronfman)
The next face-to-face ASAC meeting will take place
in Chile in September. The final dates have not yet been set. Exams
in Japan suggest that the meeting occur in the second week, so this would
in turn suggest a plan as follows: day –1 (9 September): San Pedro; day
0 (10 September): Chajnantor site; days 1,2 (11, 12 September): ASAC meeting
in Santiago; day 3 (13 September): ALMA science day. A day –2 (8 September)
may be added to allow more time in San Pedro for acclimatization and rest.
(3) - Data Manipulating Software with ALMA (Glendenning)
Please read the
background material submitted by Glendenning
and Raffi.
(5) - Calibration Meeting.
One versio of a draft agenda may be found at:
te plan.
(4) - Tuning Range Question.
The AEC asks:
The AEC asks the ASAC to comment on the following issue:
If it is not feasible to achieve adequate receiver performance over the
full RF bandwidth for the initial receivers what is the tuning range that
*necessarily* must be covered. This applies to all four initial ALMA bands,
not just band 7.
There are three important points here: (1) The firm plan
is to achieve the full RF bandwidth in the Project Book for all receiver
bands, and do so by the end of construction; (2) But the first few (~10?,
20?) frequency cartridges delivered for each band may have more limited
performance. It is for these cartridges that it would be helpful to have
the ASAC comment on the more restricted frequency range. (3) If it is necessary
that the initial cartridges have somewhat limited performance, those cartridges
will be retrofited with cartridges that do achieve the specs as soon as
the retrofits can be made available.
Details: Dear Wolfgang and John,
During yesterday's telecon, the subject of the frequency
coverage in band 7 was discussed.
As we understand it, it appears that in at least one combination,
i.e. single-ended mixers with a 4-8GHz IF, it would not be possible to
provide enough LO power on a band wide enough to cover the RF range 275-370GHz.
If we understand well, John Webber stated that he felt
it might be possible to provide adequate LO power for balanced mixers over
a LO range equal to RF-2*8GHz.
Maybe he could supply enough LO power for single-ended
mixers over a range equal to RF-2*12GHz (to be confirmed).
>From the mixer side, this means either balanced mixers
that _may_ have a 4-8GHz IF, or single-ended mixers with a 8-12 (or 4-12)
GHz IF. Of course, the combination balanced mixers, plus IF extending to
12GHz would be even better. However, either of these (balanced, higher
IF) increases the technical difficulty of mixer design and prototyping,
in a context where the technical ambition conflicts with the schedule.
>From the LO side, and if we remember well, John Webber
stated that the projected performance was at the limit of the simulation
results, i.e., it will be hard to reach.
This being said, we may, within the FE subsystem, discuss
the way to meet the specs with least technical risk, but we know that is
a difficult goal to reach. So, we propose to re-examine the scientific
rationale behind the specs (a point raised by the PDR reviewers).
As a first step, we have performed a simple exercise,
trying to estimate the relative priority in various parts of band 7. Using
the data in: http://physics.nist.gov/cgi-bin/micro/table5/start.pl we plotted
the line intensities versus frequency, overlaying the atmospheric transmission
curve for 1mm PWV. Two plots are attached, with the second one having an
expanded vertical scale. As far as we can see, there are only rather weak
lines (most intensities are recorded in Orion) between the 275GHz lower
edge of band 7 and at least 290GHz, and, to a lesser degree, up to 300GHz.
The absence of lines on our plot between 363 and 370 GHz is probably due
to lack of coverage of the observations, so we won't discuss it.
Given that the coverage of the specified RF band is at
best difficult, and may be uncertain, should not the technical efforts
be targeted at regions of maximum scientific interest. In other words,
should we not propose to the Science group to define a "first priority"
coverage of band 7, not excluding full coverage as development progress
might allow. Please note that even the more modest option of dropping 275-290
GHz from first priority yields a reduction of LO range (all other things
equal) of 15 GHz, almost twice the reduction provided by raising the upper
edge of the IF band from 8 to 12GHz (2*4=8GHz).
We provide the enclosed arguments and data so that you
may use them as you see fit to approach the ASAC and maybe obtain a reasonable
compromise between requirements and technical difficulty. You might also
consider to distribute the present message to the JRDG for consideration
at the next telecon.
With our best regards,
S.Claude & B.Lazareff
(5) Next Teleconference -
The AEC/ALG and IPT leaders will meet in Paris on 10-11 April to incorporate
Japan into the Project planning. The results of this meeting may
be discussed at the next teleconference, nominally 14 May at 1415UT.
According to one calculation, the time zones relevant
are now (1415 UT):