Hills
Hasegawa
Peck

Wootten
Emerson
Johnstone
Blain
Williams
Johnson
Bally

Testi
Laing
Cernicharo
Afonse
Hogeheijde
Aalto
Gueth

Morita
Khono
Onishi

Absent: Yamada

Cernicharo calls meeting to order.
Hills presents slide show Status update.
Some discussion of accidents, to antenna and on road.
Dummy load contains sand, has same mass, similar center of gravity and height as antenna.
There is a staggering amount of activity going on! Note in the schedule that things which were delayed are now coming along. Early science start is still late in 2010. We are investigating our ability to predict and how it might be improved.

Project Director now Thijs; Project Manager now Tetsuo. The search continues for the non-interim persons. Director search may be resolved fairly soon.

Response to ASAC Report.
Cernicharo. On points number 1 and 2 the Board is satisfied and has sought that we continue our review of software and of AIV/CSV. On Charge 3, the Board discussion led to a revision of our plan. The Board would like a streamlined approach, one team working on a reduced scale. Does the Board want outside members on the team?
RH: They would indeed like to see outside consultation; they would like to see a full range of astrophysical processes benefitting from ALMA scrutiny to be explored.
PC: To cover all of this, technical analysis and other attributes might make a large team.
RH: The Board has no numerical objective for the size of the team. Six is probably too small, twenty might be on the upper edge. With one full face to face meeting, perhaps two, this is the level I think we should address.
DJ: It seems to me that we want to feel out where the future is; that doesn't need a huge committee. A group of six or ten talking to a larger group could define the landscape as a tiger team. These 6-10 should have broad interests.
RH: The output should be a document which addresses two items:
1) AOP has substantial money planned for development. How is it justified? We must establish a solid basis for this. Some organizations are hard-nosed and demand a solid basis for expenditure of money and effort.
2) There is a shorter term issue--some technical research and development must be done in the near term. We need to identify those areas.
PC: How much?
RH: 2013-2023 this could be $100M.
PC: This is a constraint.
RH: But they don't want us to think this way; they want us to identify astronomical needs, then development to address those needs, then how to stage the development. Science is the driver. The technical folks should support the science.
PC: I agree we need a small team of the right people. Add 1 or 2 technical experts and perhaps 2 or 3 people with broad astronomical familiarity. I think that more than 12 people is unwieldy.
RH: When we set up panels we employed ASAC members, which may not be the plan now, but the ASAC would get a report from this panel.
AB: I agree that this seems a good plan so long as we get a good group.
RH: I think we should choose membership offline; the Chairs should pursue this and report back to us.
KJ: I propose Kohno join Blain and Cernicharo.
AB: We would like to receive names from ASAC members.
RH: I don't think we need discussion on the other two potential charges, but are there more items pertaining to this new charge 3?

Discussion items:
Band 10. This only arose at the beginning of the week. With tough requirements and present technology it may be difficult to meet the requirements over the whole band. A diagram is shown with the lines flagged by the ASAC in 2001. Are there reactions?
PC: The goal is 230 over 80% 344 over whole band. This is only the m ixer noise, specs apply to whole cartridge including beamsplitters and vacuum windows. So we are perhaps a factor of two away from the spec.
Tsys will probably be 1000 K. CO is important.
RH: Best HiFi mixers would not achieve this performance. So we should focus on 800-850 in Cernicharo's opinion.
PC: CO and CI will be most important given the Tsys. If there is a need to optimize, the lower part of the range is best.
RH: One could do better with lower bandwidths.
PC: For bright lines, one might consider this band; for extragalactic observations one would want to perhaps try at lower bands. I don't think one will gain a lot in narrowing bandwidth. The Board will want to review where we are at their Marseille meeting.
RH: I hear that good performance over a restricted portion of the band is the consensus favored. If we lost top third of the band that would be acceptable. The original specs come from brainstorming in the past about how many times quantum noise we could achieve. But the Niobium bandgap was not taken into account.
RH: What is the min noise performance that would be acceptable to make the effort and expense of building these receivers worthwhile? If we could do much better at B9, would B10 still be worth the bother?
AB: Perhaps this should tie to the development plan?
RL: I think these are the right questions. At the review we identified a milestone about ten months out when we would review the receiver technology. At the review we thought we should reassess at that point and decide a way forward. Some compromises would be needed; we thought more about continuum applications than lines. Resolution is higher which does give it an advantage over B9.
PC: But if we found a B10 sweet spot that would be fine.
TH: The production of B10 is funded by the JP government. It cannot be stopped to produce a savings, it would cost us.
PC: Right now it is important to have this window, even compressed in frequency range.
RH: The key item is the mixer; upgrades could be straightforward.
TH: This is the frontier. We need to start to move forward.
PC: We are certainly at the frontier, even for singledish work certainly for interferometry.
RH: We need to compare system noise temperatures.

Band 7 polarization. With changes proposed we expect at least 23 dB. This is good news. A solution for B9 seems somewhat less in hand.
The quarter wave plate now has a low level spec; science thinks it should be somewhat tougher. If there is expertise out here we would like to hear comments. They will be built experimentally at first so we need a spec for the prototype.
PC: For B9 you say there is no special polzn interest but I think I would disagree.
RH: I understand; practically speaking these receivers get -17dB but there is no easy fix. Improving this would mean an upgrade. If polzn arises in optical design it is stable and we should be able to calibrate.

On configurations I put a note out on where we are now. We have a new design and have sought to understand the effect of the decreased sidelobes provided by this design. In fact, the improvement is often not marked. Picture no 17 is an example; again the differences are at a low level. The formal specification which requires one part in 10^4 is not met; we get a little closer. Improvement costs money; say 8 pads costs $1M we would need to justify this strongly. The strong case is not yet written but we will consult the ASAC in short time.

Reports from regional centers.
ESAC: Nothing much to report. ESAC is going through a restructuring; we are more inclusive in the STC of which we are one subcommittee. Questions on membership are being considered but this will not affect our role vis a vis ALMA. Telecon next week in which we will decide some things on applying for EU funds for development of European astronomy.
ANASAC: Blain reports telecon coming Friday. F2F in late August.
EASAC: Kohno reports on workshop. Koreans attended. Two days and satellite meetings were held. Telecon will occur today.

PC: Next telecon 2 July; Blain is new Chair. This is my last telecon; thanks!
Gueth and all thank him.

-- AlWootten - 2012-05-01

This topic: ALMA > WebHome > AlmaSci > AlmaSac > ASAC7May08Minutes
Topic revision: 2012-05-01, AlWootten
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