MMA Imaging and Calibration Group

Date: 25 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

Configurations - All

Meetings Past and Future - Wootten

• AMAC Meeting --
   
• Agenda for ASAC telecon for 3 July. The Charges from the Alma Board are of special interest, here shown with Cox's plan for addressing them.
• Pierre's Proposed ASAC Text:
   ASAC Recommendation on the Long Baselines Array geometries
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   At its June 5 2002 teleconf, the ASAC was requested to `summarize the scientific and technical issues associated with the long baseline array geometries currently under consideration and to advise the ACC/ad hoc ALMA Board as to possible cost, land use, and land access impacts of which it should be aware'.
   In the current discussions on the Exclusive Use area on Chajnantor two options are under consideration regarding the long baseline (14 km) geometry: the `14-km Ring Configuration' and the `Y+ Configuration'.
   The major argument in favor of the Y+ Configuration is that it offers more continous reconfiguration, providing higher flexibility and less time lost in non-optimal hybrid configurations, which translates directly into operational advantages. Other arguments are: shorter fibers, so better phase stability; better expandability towards even longer baselines; more flexibility in re-weighting (tapering and/or uniform) data to adjust angular resolution; possibly less pads, because no complex hybrid between the 5 km Gaussian and the 14 km array is needed.
   The main argument in favor of the 14-km Ring Configuration is that this configuration would reach slightly better angular resolution than the Y+ Configuration. However, this argument is not decisive since a proper choice of the Y+ Configuration can result in similar angular resolutions than those obtained with the 14-km Ring Configuration. In addition, the possibility to expand the Y+ Configuration towards even longer baselines opens up the possibility to achieve even better angular resolution in the future. Theoretically, the 14-km Ring Configuration would provide a slightly better astrometry than the Y+-Configuration, though further studies have shown that this improvement would only be marginal under realistic observing conditions.
   Based on the above arguments, the ASAC recommend to abandon the project of the 14-km Ring Configuration, and to work on optimizing an Y+ configuration with similar angular resolution.
   
• You will find below a summary of the point of view of the Japanese radio community regarding the enhancements to the ALMA baseline project, which was sent to Pierre Cox by Satoshi Yamamoto. Although, it is not yet the final plan officially approved by NAOJ, the differences are likely to be small. In any case, the current summary will be useful to address the ACC Charge number 4 and discuss the possible enhancements at the ASAC.
    The enhancements which are considered by the Japanese radio community are as follows:
    (1) ACA: Twelve 7-meter antennae and four 12-meter antennae including cryo systems, baseline-receiver cartridges, IF and backend systems for them. The four 12-meter antennae are used for calibrating the ACA and also for accurate single-dish measurements. This will enhance the imaging capability of ALMA.
    (2) New receiver bands: Bands 8, 10 and 4. Receiver cartridges for 64 baseline antennae and 16 ACA antennae. This particularly enhances the submillimeter-wave capability of ALMA.
    (3) Second generation correlator: High resolution correlators for the 64+16 antennae. This enhances the spectroscopic capability of ALMA.
    (4) Contribution to infrastructure
    It should also be noted that NAOJ is making its best efforts to obtain a budget to achieve a value very close to the level of 1/3 of a trilateral ALMA project, so as to cover all the enhancements listed as (1) - (4). Finally, it is worth mentioning that the production of antennae of the ACA, i.e. four 12-meter and twelve 7-meter antennae, together with the enhancement of submillimeter-wave capability are considered as being strategically important items in the Japanese budget request.
    Ewine has asked IRAM to evaluate the Japanese proposal for four (or is it more?) total power antennas. Ewine also talked with Lee Mundy about strengthening the science case for the ACA, to help the Japanese defend their proposal. He was still surprised that the debris disk image did not provide a more convincing example, to the extent that we even had to leave it out of our science case. He would like to look into this in more detail in the coming months. Ewine asked me to get in contact with Lee about the science analysis of the debris images you and Brian did last year. We need to address this.
   
• Site assessment/stringency
   
• Early Science?
   
• The 3mm Receiver Design review was held earlier in the month. 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.

Calibration--Butler, Mangum

• 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).

Star Wars -- Others?

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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