Teleconference, 31 May 2001

Draft Minutes

Participants: R. Bachiller, G. Blake, R. Booth, R. Brown, Y. Chikada, P. Cox, N. Evans, Y. Fukui, B. Glendenning, S. Guilloteau, M. Gurwell, T. Hasagawa, M. Ishiguro, R. Kawabe, R. Kurz, R. Lucas, H. Matsuo, N. Nakai, M. Rafal, J. Richer, S. Sakamoto, K. Tatematsu, E. van Dishoeck, M. Walmsley, W. Welch, W. Wild, C. Wilson, A. Wootten, S. Yamamoto, M. Yun

The proposed agenda was adopted.

The minutes of the 17 May meeting were adopted and will be posted on the WWW.

1. Issues from the E-AEC

Kurz stated that actual priorities among the enhancements must await further analysis of the ACA. However, with the ‘-10%’ option defined in the charge from the ACC in its Tokyo meeting many enhancements, including the ACA, the enhanced correlator, and bands 1,4,8 and 10 can be included in the construction plan. This will be discussed at the ACC meeting. Also discussed will be models for representation of the project in Chile. An operations planning document has been prepared more as a kickoff of project wide discussion than a final plan. The ASAC will discuss this in Chile. Crutcher asked how can the ASAC get NSF to produce the extra 10%. Brown agreed that this is the crux of the problem. ACC members need to try to get NSF to come on board. They should stress the additional science that could be done. Ishiguro summarized the situation in Japan: The Director General of NAO-J has explained the Japanese guideline of 33 billion yen, or about $280M. There is no phase 1 in the plan, only budget for phase 2, but this is equivalent to $248M phase 2 plus $32M phase 1. The formal budget request will need to be in before the end of June. Competition for funds is fierce, however, and the explanation of the 3 way ALMA needs to be definite, in particular the Japanese contribution.

Hasegawa thanked the ASAC for the discussions on 17 May, after which a table with 10 rows showing draft breakdown of Japan’s contributions was delivered to MEXT, who were pleased. New questions and explanations ensued between astronomers and MEXT officials. A more detailed breakdown must be produced. Understanding and enthusiasm are spreading within MEXT.

2. Bands 1, 4 and 8 Science Cases

Ewine summarized the science cases. For the correlator cases, Guilloteau noted that the masses of ‘galaxies’ at high z might be smaller, suggesting narrower linewidths might be seen. Hasegawa noted that he had sent several suggestions for strengthening the science case. He also noted that the correlator should be called ‘future/enhanced’ and not ‘next generation’.

As for the figures for the cases for the bands, several suggestions were noted. Ewine will assemble these on the weekend for distribution.

3. DSB-SSB-2SB

There was considerable discussion on the memos from the project scientists on this topic. Some discussion ensued on the fractional time spent on continuum observations. Guilloteau produced new receiver temperature estimates across the bands and arrived at sensitivity ratios based on these and assumptions on the fractional time on continuum. Wootten used existing receiver temperature estimates and calculated the DSB/SSB breakeven point for the fraction of continuum time. Guilloteau noted that there was a break point between ‘high’ and ‘low’ frequency performance and suggested that the advantages of SSB performance for the lower frequencies were more pronounced. Rafal asked whether if for cost, reliability or other technical issues the project would likde to go with DSB even at low frequencies -- what would be the science impact. Stability might also enter into the equation. This has not been studied. Guilloteau noted that bands 6 and 7 would benefit most from SSB designs. Discussion of 2SB vs. SSB ensued. 2SB offers certain technical advantages but has never been demonstrated on a telescope and results in a more complex receiver. One current band 6 design employs SSB performance with sideband change via a bias swap.

The receiver liaisons will draft an ASAC recommendation based on the discussion.

4. Software

Chris Wilson introduced the Canadian proposal for a real-time imager, a more ambitious proposal than the baseline aimed at ALMA users who are not sophisticated radio astronomers. Richer pointed out the relevance of the SSR documents. Guilloteau and Glendenning noted that the level of effort was perhaps twice what was in the baseline plan. It was noted that communication needed to be improved. Ewine called for input from the SSR by the July ASAC telecon, in particular a summary of the top-level science requirements on this aspect within the current WBS.

5. Next ASAC teleconference

The next ASAC teleconference will take place on Thursday 14 June at 14:15 UT.