Minutes for meeting Wed, 19 January 2000 at 12pm EST (17:00 UT).
Past minutes and listings of relevant memos and publications are found at ALMA Configuration Working Group Page
--------
The ASAC wants a report from the configuration working group during their March 10-11 meeting in Leiden. Several of us will be present at the meeting, and we will make a report on ongoing progress to that point.
--------
Jennifer Neighbours (jneighbo@nrao.edu) is doing the administrative
stuff. Please let her know as soon as possible if you plan to attend. We
need a head count. Later, please let her know your detailed travel
plans. She can help with local arrangements.
Date: 2000 March 20 - 21 (Monday - Tuesday)
Location: Tucson, AZ (USA)
Varsity Suites Hotel
Speedway & Alvernon, 2 miles E of campus
rooms @ $80 /night plus tax
--------
Some of the configuration issues listed below can serve as fundamental tools for our future works, and a more rapid progress may be achieved by dedicated small subcommittees. Each subcommittee discussion leader/moderator will make a report at the face-to-face meeting and lead the subsequent discussions. Please let M. Yun know if you want to lead the discussion of one of these topics or if there are other issues that may be best addressed this way.
Topographic constraints and digital masks. B. Butler has already made several preliminary togographic masks based on existing digital elevation models. A. Webster has agreed to moderate the discussion, and S. Radford and J. Conway are also contributing to this effort. The 10+ km configuration is a special case, entirely limited by the topographical and political boundaries. A memo is being prepared by Yun and Radford.
Image library. B. Butler already has some images donated by the old MMA Advisory Committee. F. Villiafond favors using artificial images that may be better suited for evaluating imaging performance (e.g. greater spatial frequencies than available from existing data). We should query ASAC for more input on this matter as it was previously suggested that the test images should be science driven. We need the broadest participation possible in this discussion. Bryan and Francois will lead this discussion.
Quality metrics for judging imaging simulations. Developing detailed quality metrics may not be possible in the short time we are given, but we still need to develop a set of quantifiable working metrics for comparing different simulation results. Existing experiences such as by M. Holdaway, L. Mundy, T. Helfer, L. Kogan, J. Conway, E. Fomalont, and F. Villiafond are highly valuable. No discussion moderator has been chosen, and we need someone to volunteer soon.
Simulation details. We want various configurations to be directly comparable, and any apparent differences may be the result of using different algorithms. This was a late entry in the discussion, and thus we do not have a discussion leader. People who voiced interest on the topic includes T. Helfer, F. Villafond, and M. Holdaway.
Compact configuration. Several unresolved issues remain such as the need for variations in N-S elongation, packing/transporter restrictions, etc. Related issues are the general N-S elongation and hybrid configurations. Helfer, Holdaway, and Radford have contributed to this discussion previously. Yun will document the discussions on this topic. Zero spacing was also brought up as a relevant topic, but it is a problem independent of configuration design.
Full synthesis versus snapshots. Most configuration design efforts have focussed on the best snapshot imaging capability, with the assumption that it can be generalized into any full synthesis. Recent proto-memo by Conway addresses this point. Yun will document the discussions on this topic also.
Multi-configuration synthesis. S. Guilloteau noted that while the old MMA project requirement called for a complete imaging capability in each configuration independently, multi-configuration synthesis was given more weight in the LSA discussions. A unified approach is needed as it may have a major impact on the configuration design philosophy.
Dynamic Scheduling. Not discussed because we ran out of time, but this could severely impact the mode of array operation. M. Wright has written a relevant memo on this topic recently.
Configuration cost and Mosaic performance. Not discussed directly during the meeting, but they are identified as important factors for comparing different configuration designs by different individuals. Yun reminds the simulators to consider the robustness of their proposed configurations to random losses of antennas (e.g. 10%) from the array.
--------
Several implicit agreements on the basic configuration parameters such as the need for a compact configuration and a 10+ km configuration have already been reached at the Toronto workshop. The overall style and the mode of operation for the "intermediate" configurations is the key remaining issue. Several competing designs are considered by different workers, and evaluating their relative merits will require the specific rules and tools developed by the topical groups listed above. All workers are encouraged to continue developing their own software (pipeline?) for simulations in the meantime so that we can all start testing our designs once the library, metrics, etc., are agreed upon.
--------