Teleconference, 17 May 2001
 
 

Draft Minutes

Participants: G. Blake, L. Bronfman, R. Brown, P. Cox, R. Crutcher, D. Emerson, N. Evans, Y. Fukui, S. Guilloteau, M. Gurwell, T. Hasegawa, R. Kawabe, R. Kurz, J. Payne, M. Rafal, J. Richer, S. Sakamoto, P. Shaver, k. Tatematsu, E. van Dishoeck, M. Walmsley, W. Welch, W. Wild, C. Wilson, A. Wootten, S. Yamamoto, M. Yun
 
 
 
 

The proposed agenda was adopted, with one addition: a report by T. Hasegawa on the situation in Japan, following agenda item (1). Operations will be discussed at a later date.

The minutes of the last teleconference were accepted after one minor change, and will be posted on the WWW.
 
 

1. Summary of the Paris Meeting

S. Guilloteau summarized the important results from the Paris meeting of 10-11 May:

1. There was unanimous agreement on how to proceed with the antennas. Following comparison of the three prototypes, a common design will be selected and fabricated, and the antenna groups agreed on a vertical division for the construction work. This means a single, commonly accepted, design, to be produced according to blueprints by whichever contractor any of the 3 partners may select. Each partner will thus provide as "in-kind" contribution 21 antennas. One will provide an extra antenna to match the total number of 64.
2. All agreed to the IPT (Integrated Product Team) structure. It was also supplemented by a "client/vendor" (or "customer/supplier") approach in which components required by some packages are provided by a unique "supplier" to "customers" for integration. The "customers" are ultimately responsible for the definition of the deliverables.
3. There was good progress in defining the division of tasks in the 3-way project.
4. There are significant cost increases, which may total as much as $40M, arising from better definition of several areas of the project (in particular software, receivers, and possibly antennas), and as a result it was felt that it would be difficult to accommodate the ACA within the budget.

The ASAC concluded that there is at the moment no basis to change the scientific priorities that were established at the Florence meeting, and strongly supports continued studies of the ACA. S. Guilloteau said that the studies will take six months. The ASAC would like to have an intermediate

(progress) report on the ACA at its face-to-face meeting in September.

2. Report from Japan

T. Hasegawa reported that discussions have already started with MEXT. In view of the competition for funding, the ALMA case must be strong and consistent. An immediate requirement, needed by the end of the week, is information giving a clear definition of the project; this is essential for Japanese funding for 2002. It is also very important for Japan that its participation is seen to provide major enhancements, and the proposal being prepared includes Band 10, the enhanced/future correlator, and one more frequency band.

R. Crutcher asked whether the ACA could not be considered such an enhancement. T. Hasegawa replied that it could be, but the recent cost increases have made it very difficult financially. He also commented that the correlator cost had been much reduced. J. Welch pointed out that, if Moore’s law continues to apply, a correlator would be far less expensive ten years from now, so it may be sensible to stick with the baseline correlator at present. T. Hasegawa replied that the current schedule to build the Enhanced/Future correlator takes into account the benefit of such a reduction in the production cost. It was suggested that savings could possibly be made in some other areas of the project to make the ACA possible, and R. Brown pointed out that the presently estimated costs are not final, and could conceivably become smaller.

To conclude, the ASAC agreed that the components proposed by the Japanese delegation to their ministry MEXT -- including the enhanced/future correlator, Band 10 and one additional receiver band -- are among the scientifically interesting enhancements to the baseline two-way project.
 
 

3. Front End Specifications

W. Wild mentioned some points in the "Specifications for the ALMA Front End Assembly" that need to be finalized or clarified. One is the TBD maximum phase change resulting from the reselection of a particular frequency band at a given antenna (Sec. 3.8). S. Guilloteau will formulate a proposed specification with an explanation by 1 June. This will be distributed to the ASAC for comment before being sent on to the Receiver Group. E. van Dishoeck will forward other suggestions on the document received from the ASAC within one week to the Receiver Group. W. Wild noted that some of the numbers given as "goals" in Sec. 3.4 may not be feasible, and S. Guilloteau commented that the quoted performance should be based on specifications rather than goals.
 
 

4. Science Cases for Bands 1, 4, and 8

The science cases for these bands were briefly reviewed, to prepare for prioritization if and when required.

J. Richer outlined the case for Band 1, and stressed the several unique scientific aspects of this band. The numbers are being finalized, in particular the comparisons with the EVLA. M. Yun suggested that the phase stability statement be removed, and S. Guilloteau suggested that the cost statements also be left out – both were agreed.

M. Yun presented the case for Band 4, and highlighted the advantage of the atmospheric transparency of this band. Astrochemistry and redshifts are major drivers. This band will also be important for continuum measurements and photometric redshifts (although the latter may superseded by spectroscopic redshifts by the time ALMA is operational). CO redshifts in the range 0.4-0.8 and astrochemistry are major drivers.

The case for Band 8 was summarized by S. Yamamoto. Of greatest importance will be the ground state fine structure [C I] line, probing the transition between the atomic and molecular gas. The CO (J = 4-3) line is also an important tracer. M. Yun and C. Wilson noted that Band 8 will also be important for the redshifted [C II] line. J. Richer commented that the case should explain the importance of high angular resolution here, and A. Wootten noted that the ACA may be important in this case to recover the flux and aid in interpretation.

Updates of the science cases are to be sent to E. van Dishoeck by Tuesday 22 May, taking into account the comments from the ASAC. The material will then be collated into a single document to be distributed before the May 31 telecon.
 
 

5. Future Correlator Science

Referring to the case prepared by A. Baudry and others, S. Guilloteau noted the potential imact of a large future correlator. The large bandwidth, higher sensitivity and larger number of channels will be particularly important for high redshift galaxies surveys. Other projects requiring simultaneous observations of several lines to provide homogeneous data sets and planetary studies will also greatly benefit. M. Yun commented on the high data rates required.

6. Discussion

The above topics were briefly discussed together in the context of the overall project. It was agreed that no further prioritization of the receiver bands and correlator would be made at present, but that the ASAC should be consulted if and when the project decides that choices have to be made. The project is urged to continue the study of the feasibility of the ACA. It was also stressed that an adequate upgrade plan and budget is needed in the operational phase.
 
 

7. Recommendations

As a result of the teleconference, the following statement and recommendations were prepared, to be passed on to the EAEC and the EACC:
 
 

ASAC RECOMMENDATIONS

====================
 
 

The ASAC, at its May 17 2001 telecon, was informed of the results from the Paris three-way meeting May 10-11 2001 and the increased cost estimates. In addition, the Japanese delegation outlined a proposal for components to be included in their proposal to the MEXT ministry on May 18 2001.
 
 

The ASAC has the following recommendations:

1. The ASAC re-affirms the importance of the Atacama Compact Array and its high scientific priority. It urges the project to continue to study its feasibility, present an interim report at the face-to-face ASAC meeting in Chile in September, and investigate ways to accommodate the ACA financially in the project.

2. The ASAC re-emphasizes the unique scientific importance of Bands 1, 4 and 8, and requests continued consultation should further prioritization be needed.

3. The ASAC concurs that the components proposed by the Japanese delegation to their ministry MEXT -- including the enhanced/future correlator, Band 10 and one additional receiver band -- are among the enhancements of considerable scientific importance to the baseline two-way project.

4. The ASAC urges the agencies to make sufficient funds available to allow or substantial R&D and instrumentation investments in the operational period of ALMA such that the full complement of receivers can be implemented within a reasonable timescale and that upgrades to the receivers can be maintained on a consistent schedule.
 
 

8. Next ASAC teleconferences

A special teleconference of the ASAC will take place on Thursday 31 May at 14:15 UT, to provide input for the EACC meeting in early June.

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