MMA Imaging and Calibration Group

Minutes for meeting Tuesday, 18 June 2002 at 4:00pm EDT.

Date: 18 June 2002

Time: 4:00 pm EDT pm EDT (2:00 pm Socorro, 1:00 pm Tucson)

Phone: (434)296-7082 (CV SoundStation Premier Conference phone 3rd floor).

Past minutes, etc on MMA Imaging and Calibration Division Page

Agenda

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News. -Wootten

News from my point of view.

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Configurations - All

Last week Angel described the studies which should lead to a memo on or about the beginning of July. The new plan utilizes 6 antenna moves between 'configurations' for an increment factor of 32 per cent. The Boone software has optimized for 2 hr observations, declination -42 from Chajnantor. This results in two sets of configurations for the tight and loose masks, 42 pads from Conway's largest configuration to the largest in the Y+ array. Details depend on Conway's result, now under construction. Angel thinks that comparison to a strict VLA-style wye would be illuminating. Imaging qualities need to be assessed, a relatively easy task with the IRAM software. Cost differentials also need to be assessed and are being reviewed. General opinion is that although the Chascon necklace may offer some advantages in astrometry, they will not be overwhelming.
Please see contribution from Mel Wright.

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Meetings Past and Future - Wootten

ACC Teleconference 18 June 2002.
Minutes from ASAC telecon for 5 June. The Charges from the Alma Board are of special interest, here shown with Cox's plan for addressing them.
The 3mm Receiver Design review was held last week. Documents may be read at Sitescape. One question is what the sensitivity should be at the band edges, particularly near the CO 1-0 line. AW thinks that since in this region the atmosphere is the limiting factor, poorer receiver performance can be tolerated up to the point where sensitivity is no longer dominated by the atmosphere. We need to work this out. Best performance should be in the 90-95 region, where we expect workhorse use for phase correction. In the extension 84-90 GHz, the ASAC opined that poorer performance could be tolerated. Ideally, we should know what the receiver folks might supply. As SG stated in memo 393: There is significant sensitivity gain in Band 3 between receivers with Trec = 50 K SSB, and receivers with Trec = 6h*nu/k + 4 K. The later should be kept at least as a very serious goal for ALMA.
Change request for Band 7. John Webber checked with Eric Bryerton about reaching 373 GHz with Band 7. The LO is not a problem. It is now specified within the Front End LO group that the LO will reach the nominal band edges so that mixer designers can test performance beyond the nominal band--useful for evaluation. Thus, the actual LO frequency will go to 370 GHz for Band 7.
The JAO met last week in Charlottesville, Weds-Fri.

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Calibration--Butler, Mangum

Sideband gain ratio ALMA MEMO #393
Conclusion and Recommendations

1. Receivers for band 9 and 10 should be DSB, 4-12 GHz IF mixers.
I agree with this conclusion.
2. Receivers for band 3 to 7 should be 2SB, 4-8 GHz IF mixers. This offers the best compromise in performance and saturation level.
In discussions last week with SG, I told him that I disagree. I think we still disagree.
3. An upgrade path starting from DSB mixers with 4-8 GHz IF, and finishing with 2SB 4-8 GHz IF mixers is the only one providing full performance of all receivers at all time.
I agree with this conclusion.
4. The correlator must allow sideband separation (by Walsh functions) to be able to use DSB receivers.
I agree with this conclusion.
5. DSB receivers which will be upgraded to 2SB must provide a double output.
I agree with this conclusion.
6.
I agree with this conclusion.

Issues: Calibration Group Set Up
Because ALMA is going into the construction phase, the current way we have been handling ALMA science documents requires some modifications. While in the past we have been exploring a lot of ideas, ALMA now requires detailed implementation. It becomes important for the project to be able to distinguish properly between ideas, working documents, and specifications. It is currently difficult for an engineer to figure out whether a=20 a particular idea exposed in a document must be implemented or not.
We have been using in the past ALMA Memos and the Project Book for our purposes. The ALMA project has now installed the=20 "SiteScape" server which is intended to be an archived repository of all controlled ALMA documents. The Project Book will evolve towards a more simplified description of the ALMA project.
Because "SiteScape" is a restricted area, and because a more open approach is required for the Science aspects of ALMA, we propose a "reviewed memos" approach, which attempts to keep the open spirit of the Memos series, while implementing some control over the most important documents. The basic idea is to have "reviewed memos"=20 appearing both in the Memos series and in the SiteScape documentation system, with a clear "stamp": "Reviewed by the Science IPT".
The 'reviewed memos' process will be as follows:

1 - A memo is submitted to the normal ALMA memo series.
2 - If it is perceived that the memo is relevant to the=20 issues addressed by our group, and contains material=20 which might affect decisions made by the project in=20 some way, then it will enter into the review process. The decision will be made by the appropriate group heads (Bryan Butler for calibration issues, John Conway for configuration issues, the project scientists for other issues), in concert with the project scientists (Stephane Guilloteau and Al Wootten). The author(s) will be queried as to whether it is=20 acceptable for this memo to be reviewed. An author may also specifically request that a memo be reviewed, but this does not guarantee that it will be reviewed.
3 - The review process will consist of the following:
a - Formal reviewers will be asked to review the memo, these reviewers to be selected by the appropriate group head and/or project scientists;
b - Others may review the memo, on their own initiative;
c - Reviews will be collected by the appropriate group head and/or project scientists and forwarded to the author(s); Reviews submitted to the mailing lists are archived automatically.
d - The author(s) will prepare a reply to the reviews;
e - The author(s) will prepare a new version of the memo, which will then be reviewed by the appropriate group head and/or the project scientists;
f - If approved, the memo will be marked as such, and will be included in the sitescape collection of=20 documents, along with the associated review=20 documentation. Note that the author(s) may also submit a revised memo to the regular memo series if desired, and the revised memo may be marked as a 'fully reviewed' memo (wording TBD).

This is a significant departure from the way that we have been operating in the past, with a much more structured and formal mechanism for the memos (at least some of them). We note, however, that the computing division has been using a similar mechanism for *all* of its memos (with admittedly significantly fewer memos). Additionally, no author is *forced* to have a memo go through the new review process, it is rather a choice to be made, in combination with the appropriate people from the project itself. We feel that this added structure and formality is necessary, given the point that we are at in the project, and the fact that we feel that we can no longer operate in the freewheeling manner that has been characteristic for us in the past.
Stephane Guilloteau, Science IPT Leader and ALMA Interim Project Scientist (AIPS)
Al Wootten, Science IPT Deputy Leader and U.S. Project Scientist
Bryan Butler, Calibration Group Head
John Conway, Configuration Group Head
New Memo 422 (for review). New Memo 423 (for review).
Other Lucas' list of simulation requirements to be discussed in Granada

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Star Wars -- Others?

Any other reviews of the movie? How about all those exoplanets!!
I looked through the 90 odd exoplanets in the databases. Some interesting representative numbers emerge.
If we can measure 0.1 mas, about half the systems should have a wobble detectable by ALMA (I didn't screen for declination, however).
Three planets will be brighter than 1 microJy, assuming Jovian characteristics. 29 more will lie between 0.1 and 1 microJy, at 650 microns. These won't be detectable without heroic effort. Even processing 32GHz doesn't qualify for heroism.
All stars but ten will be brighter than 1 mJy at 1300 microns. Nearly all are brighter than 5 mJy at 650 microns. One (the only giant) should be 10 mJy at Qband (maybe we should check it out).
I'm working on the debris disk numbers but I think any debris worthy of the name will be detectable easily with ALMA.
ALMA's role in characterizing planets around known exoplanet systems is through astrometry, through detection of residue disks and through direct imaging of protoplanets.
Comments?

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Upcoming Meetings - Wootten

May 2 ASAC agenda.

MAY 6-9 Astrophysics of Life Space Telescope Science Institute Wootten attending

May 24 ESO Committee of Council

June 2 - 6 AAS Meeting Albuquerque

JUN 18-21 Scientific Frontiers in Research on Extrasolar Planets at Carnegie Institution See ALMA abstract. Program now online with two ALMA posters:
Session: Ground-based Planet Search Instruments: ALMA
Jean-Francois Lestrade, Observatoire de Paris/LERMA
"Astrometry at millimeter wavelengths with ALMA to search for extrasolar planets or to determine their orbits"
Henry Alwyn Wootten, National Radio Astronomy Observatory
"Extrasolar Planet Research with the Atacama Large Millimeter Array"

JUN 24 AMAC Meeting Munich

AUG 17/24 URSI General Assembly, Maastricht, the Netherlands Butler attending

AUG 22/28 SPIE Symposium on Astronomical Telescopes and Instrumentation, Waikoloa, Hawaii. Brown, Wootten attending

SEP 9-13 Winds, Bubbles and Explosions

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Travel

Oh, always

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