MMA Imaging and Calibration Group

Minutes for meeting Mon, 9 November 1998 at 11am ET.

Date: Monday, 9 November, 1998

Time: 11:00 am EST (9:00 am Socorro, 9:00 am Tucson)

Phone: (804)296-7082 (CV SoundStation Premier Conference phone).

Past minutes, etc on MMA Imaging and Calibration Division Page

Minutes

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In attendance: CV: Wootten; AOC: Glendenning, Rupen, Butler, Yun TUC: Mangum, Helfer, Radford.

Report from antenna meeting in California -- Butler



On 4 Nov, Butler, Brown, Woody, Churchwell, Carlstron, Welch and Blitz met at Berkeley to discuss antenna diameters. The deliberations concentrated on science drivers in the morning, and technical issues in the afternoon.

Conclusions from the science discussion were:

  • A class of interesting single-pointing observations exists--distant galaxies, some stars, Kuiper Belt Objects and asteroids, and similar small objects. For these observations, nD2 should be optimized.
  • In spite of the above, most observations with the LAMA will be mosaiced--notably, star formation regions will need to be mosaiced, to understand how the protostellar envelope ties in with the inner region. Interpretation of a single pointed image made of the central star formation region cannot proceed on sound footing without knowledge of the surrounding region. For these observations, nD should be optimized.
  • Any diameter can provide these mosaiced images if the antennas meet specifications, including total power capability.
  • Sensitivity increases with diameter.
  • A minimum sensitivity exists with which the array will be capable of addressing high z problems, as well as gaps caused by forming planets in protoplanetary disks. This drives nD2 upward.
  • Similar quantitative arguments for characterizing a minimum value for nD for the LAMA need to be made, and are currently being formulated.

    On the technical side, one can "push" in one of three areas during development--antennas, electronics, or correlator. It was thought (given later argument) that the correlator wouldn't necessarily need to be agressively pushed. If it is decided to push antenna design, there is necessarily a large risk involved. The antenna is a major expenditure, and possibilities for upgrades to the antennas are limited. The antennas should therefore be built with the most advanced technology which poses a minimum of risk. The electronics offer an opportunity for major technological advances. However, if these advances are not realized, we will have missed the opportunity to have pushed on antenna design. An example where antenna design was pushed is the GBT. An example where electronics design is being pushed is the 1 Hectare Telescope.

    The cost equation was revisited, including scaling with D, receiver number, maintenance and operations (scales as ~0.5n) and risk analysis. A study by Napier indicated 30% contingency for 10m antennas and 35% for 12m was prudent. Then antennas plus receivers for an LMA which total the $200M expected budget (for antenna + receiver costs only) include:

  • 93 x   8m   =>   nD ~ 744;   nD2 ~ 5952;   A ~ 4675 m2
  • 67 x 10m   =>   nD ~ 670;   nD2 ~ 6700;   A ~ 5260 m2
  • 48 x 12m   =>   nD ~ 576;   nD2 ~ 6912;   A ~ 5430 m2
  • 31 x 15m   =>   nD ~ 465;   nD2 ~ 6975;   A ~ 5480 m2

    These numbers should not be taken as real estimates of the number of antennas in the final LAMA, but rather as illustrative of the tradeoffs between number of antennas, and the two products nD and nD2. This analysis will be done more carefully by Brown. It seems apparent from the above table that in order to optimize both nD and nD2, either the 10m or 12m diameter is preferred. 8m pays a large penalty in nD2. 15m pays a large penalty in nD. There is only about a 15% difference in nD, and about a 3% difference in nD2 between the 10m and 12m designs. However, the risk is much greater with the 12m diameter. The NRAO 10m design scaled to 12m would be unable to meet the current specifications. The OVRO 10m design (with its many clever features) scaled to 12m is just barely able to meet the specifications for pointing and surface accuracy. The 10m (or 8m) design could meet the specifications. However, the total number of antennas (and hence receiving systems, cryogenics systems, etc...) is about 50% greater than for the 12m antenna. This material will be written up by the members present, and submitted to the MAC for consideration.

    Butler visited the lab at Berkeley and reported that the three load cal system is working well in the lab, whizzing along with a 50ms integration at each load, with little apparent vibration. It is hoped that this will soon be mounted on an antenna.

    Butler reported that OVRO plans to use 3 WVR channels this winter, and that the BIMA/U. Md. backend might arrive at the site sometime in January. Radiometer feedback problems in the VLA WVR have been repaired and tests on antennas should begin within several weeks.

    MAC meeting -- Wootten

    Wootten will report on the Frequency White Paper, and fast switching. Butler will report on 22 GHz water vapor radiometer plans and operations. Yun will report on 183 GHz water vapor radiometer plans and operations. Mangum will report on calibration issues. Wootten will also lead a discussion of the Scientific Meeting planned for next year.

    Project Book -- Wootten

    Wootten is updating Chapters 3 and 13; Helfer is working on Chapter 15, and Brown is working on Chapter 2. Drafts are due 11/16/98 with final copy by 11/30/98.

    Standard Talk -- Wootten

    Wootten and Smiley are developing a standard presentation based upon a suggestion of Brown's. This is developing on the MMA Imaging and Calibration Division Page for the moment. Note that copies of most of these viewgraphs were distributed to Weatherall in Socorro, Webb in Tucson, and Smiley has sets in Charlottesville. Uson also has Spanish language versions of some of these. A Spanish version of the description book is also available (ask C. White for the August 1998 version).

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    Notes from Division Heads Meeting Minutes:

    The WBS is complete, and in "published" format. The complete Gantt chart (a listing of all tasks with an attached graphical timeline) is available at http://www.cv.nrao.edu/~rsimon/mmagantt.pdf. An index is included, so you can easily find your favorite section.

    The WBS Dictionary is also now available, also with an index page, at http://www.cv.nrao.edu/~rsimon/wbsdict.pdf.

    Finally, the list of milestones is on line at http://www.cv.nrao.edu/~rsimon/mmamlstn.pdf.

    Frequency Bands for Evaluation Receiver and First Production Receiver

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    The question is what bands will be used for the evaluation receivers at the VLA test site and for the first receiver that is placed in Chile. This was discussed in the receiver meetings. The official decision is that the final system band edges will conform to Table 3 of MMA Memo 213.

    The Evaluation Receiver at the VLA site will have 30 GHz, low end 90 GHz, and 230 GHz. The evaluation receivers are not constrained to stick to following Table 3.

    The first receivers in Chile (arriving in early 2004) will cover the low end 90 GHz and 230 GHz. In late 2004 we will add the 650 GHz.

    To make the WBS, Project Book and other documentation consistent, Simon will change all references of 170-245 GHz to 230 GHz. But the Project Book and other documentation will state that we are doing development work on other bands.

    Japanese Meeting ----------------

    The Japanese are trying to gain more support by staging this high profile meeting in government plaza. They are hoping to get more input from government bureaucrats. There is much competition for the monies from the high-energy physics and gravity wave sciences.

    Europe Meeting --------------

    ESO and the UK initialed the MOU on Friday, 06Nov. The initialization of the MOU means that the European Coordination Committee (ECC) has been set up. The ECC will consist of mainly bureaucrats not necessarily astronomical people. This will allow them to assign a Project Manager and Project Scientist within 31 days. The Dutch, Germans, and French also initialed, which means they are giving money outside their usual ESO contribution. This will enable them to have a stronger voice. The combined funding is $15 M. The Dutch contributed to the receiver development, the Germans to antenna development, and the French have not decided.

    -------- Action Items 9 Nov98

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    URSI Meeting (Radford) Schedule

    -------- Travel

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    T. Helfer: 26Nov-09Dec (Tenerife)

    A. Wootten: 18-19 Nov (Green Bank) 20-22 Nov (Chi) 12-17 Dec (AOC)

    J. Mangum: 20-22 Nov (Chi)

    M. Yun: 20-22 Nov (Chi)

    B. Butler: 3-5 Nov (UCB) 20-22 Nov (Chi)

    S. Radford: 20-22 Nov (Chi)