ALMA Science Advisory Committee Teleconference 13 November 2000 Draft Minutes Participants: G. Blake, L. Bronfman, Y. Chikada, P. Cox, D. Emerson, S. Guilloteau, N. Nakai, M. Rafal, J. Richer, N. Scoville, P. Shaver, E. van Dishoeck, M. Walmsley, W. Welch, A. Wootten, S. Yamamoto 1. Minutes of last Teleconference The minutes of the last teleconference were accepted, subject to a few revisions. 2. Report on ACC Meeting S. Guilloteau gave a summary of the October meeting of the ACC. The most important development was a formal statement of interest from Japan in joining as a third equal partner. The goal is to complete the definition of a 3-way project by the fall of 2001. M. Rafal said that the ACC had given guidelines to the AEC in which savings of at least 10% per partner should be realized relative to the current two-way project. J. Welch asked about the implications for the ASAC. Full Japanese participation in the ASAC is now planned, and the Japanese members will be announced at the next ASAC teleconference. 3. Extension of Band 3 to Lower Frequencies L. D’Addario’s note on the proposed extension of band 3 to lower frequencies was discussed, although it was felt that comments from the receiver group were also needed before final conclusions were reached. There was general agreement that an extension to 86 GHz is important, particularly to access the J=1-0 SiO line and the J=1-0 lines of HCN, HCO+ and their isotopes, and extension to even lower frequencies is desirable. On the other hand, provision of band 2 becomes more likely with Japanese participation. It was agreed that, while there should be no compromise on the performance in the 89-116 GHz range, the possibility of extending to lower frequencies should be pursued. The ASAC would like to receive from the JDRG an estimate of the degradation in performance below 89 GHz if Band 3 were extended down to 86 GHz, 84 GHz and even as far down as 80 GHz. 4. Scientific Merit of the Enhanced Correlator Concerning the memo from T. Hasegawa, N. Nakai, and S. Yamamoto, N. Scoville and S. Guilloteau commented that the European and Japanese plans for an enhanced correlator are converging towards similar specs, although both are concerned about the implied data rate. It is important to pursue the technical development studies before making final decisions. S. Guilloteau said that the enhanced correlator, particularly 3-bit, could bring a major efficiency gain relative to the investment, provided it has no sensitivity loss for the “normal” science cases. It was agreed, in line with the proposal from Hasegawa, Nakai and Yamamoto, that the ASAC should discuss the scientific merit of the enhanced correlator regardless of its technical implementation, along with some science examples. This will be done at the Florence face-to-face meeting based on documents written by the correlator teams prior to the meeting. S. Guilloteau also commented that the compact array should work as a stand-alone array, and thus can be accommodated by the baseline correlator. Also, there should be no trade-off in which the number of 12m antennas is reduced below 64, as at least this number of antennas is required for good imaging quality. 5. Site A. Wootten reported on a meeting that took place on Monday 7 November in Charlottesville with A. Readhead and others to discuss the Caltech experience on the site. Overall the weather had been excellent, giving one hundred times more efficiency than at Owens Valley. However 10% of the time had been problematic, with snow and sometimes liquid water in the atmosphere. Wind was not a real problem, and appropriate site development and engineering can alleviate the problems due to snow. A. Readhead suggested that additional relevant specs be made for the antennas. There is a plan to correlate the CBI results with the 225 GHz tipper 'stare mode' results. The 183 GHz radiometer also 'stares' and data from either of these should result in a measurement in total power fluctuations which may be compared to CBI measurements, especially at times when liquid water appears to be present. A memo on this meeting has been prepared. A. Wootten also reported that comparative contemporaneous studies for corresponding time periods have now been made for Chajnantor vs. Pampa la Bola: Radford's preliminary result is that during 1999 June - December tranparency was 15-30% better over Chajnantor than over Pampa la Bola. Butler finds that the median phase fluctuations at Chajnantor are ~12% better than at Pampa la Bola, averaged over all times. During the lowest rms phase fluctuations, Pampa la Bola fluctuations are 43% worse than at Chajnantor. 6. AOB A. Wootten announced that both the NSF and the NRC have now signed the agreement for Canada’s participation in the project. Canada’s share will be 10% of the North American side of the project. 7. Next Meetings The next face-to-face meeting of the ASAC is now confirmed to take place in Florence on 23-24 February. About 35 participants are expected. All are asked to e-mail M. Walmsley indicating their likely participation as soon as possible. ----------------------------------------------------------- Dear Interested Participants in the ASAC Face-to-face meeting, This concerns those interested in attending the Florence face-to-face meeting of the ALMA ASAC on Feb 23-24. We have reserved for this meeting the "Sala Bargello" of the "Convitto della Calza" , Piazza della Calza 6, close to the Porta Romana on the south-western corner of the Florence city walls. This is within walking distance of the Florence city center and all the tourist attractions. We have had some problems organising hotel rooms for the meeting. We first thought that the rooms within the Convitto itself would be available and that turned out eventually not to be the case. We have therefore made a pre--reservation of blocks of rooms in two neighbouring hotels : the "Hotel Classic" on Viale Machiavelli and the Pensione Annalena on Via Romana. The charges per night are of the order US$ 100 for the Hotel Classic and $125 for the Pensione Annalena. We need to know fairly soon how many people intend to come and therefore request you to send us a statement of intent using the "form" attatched below. We want this preliminary information prior to Dec. 15 . Those who send us this information will be assigned a hotel and requested to contact the hotels directly by Fax sending credit card information etc. Those who do not reply are warned that they will be subject to the wild and wooly struggle with the Florence hotel booking system. This can be fun but we leave it to you. ------------------------------------------------------------------ Name : Affiliation : e-mail : Fax : Telephone : I intend to attend the Florence face-to-face meeting of the ALMA ASAC on February 23-24 2001. I would like a room reserved as follows: Single : Yes Double : Yes Other : Explain Date of Arrival : Date of Departure: Send to masini@arcetri.astro.it and walmsley@arcetri.astro.it ------------------------------------------------------------------- The next ASAC teleconference is scheduled for Monday 11th December at 1515 UT.