Minutes of the Science IPT Telecon 9 March 2004 Hogerdeijde, Wootten, Bacmann, 長谷川哲夫 Hasegawa, Kawabe, Tatmetsu, Conway, Laing, DiFrancesco, C. Wilson, Mangum Lucas, Pety, Guilloteau, Holdaway, Hills Wootten gave a quick summary of action items from the last meeting, followed by a terse summary of milestones, updated for the AMAC meeting. For most Level 2 Milestones the Science IPT is doing well, but many of the Level 3 and below milestones have suffered delays. These are not critical path milestones, but they are significant secondary goals. Wootten briefly discussed the Calendar. The Operations Group draft has been passed to the Executives by the JAO. The Board is expected to receive a version to pass to the ASAC by the end of the month, when the Board meets in Socorro. A subgroup has been tasked with identifying 'modes' for Early Science. In conjunction with the Operations Plan, Robert Laing has drafted a commissioning and science verification plan. IPT members interested in participating in the evolution of this activity should contace Laing or Wootten. Plans for the ASAC meeting 10-11 May in Cambridge are firming up. The Science IPT will be asked to provide some support for them as they frame responses to the Charges which the Board has presented them. Wootten discussed the System Design Review conducted during ALMA Week. A report will be made available when the committee finishes its drafts. A table of modes for the correlator with the new tunable filter is attached to the agenda. There are clearly benefits for science, but studies continue on the design. To suppress aliasing, subchannel windows need to be overlapped. Science specifications should be set to determine the allowable errors in the overlap region. Baudry showed an example: Overlap of two spectral points of each subchannel resulted in 0.5% amplitude and 0.3 degree phase maximum errors, ending up with 93% usable Bandwidth. Additional overlap can suppress these errors further at the expense of usable bandwidth. At the ATF antenna characterization continues; radiometry continues on the VertexRSI antenna. This should start soon with the AEC antenna. Kawabe summarized discussions during miniminiALMA Week in Tokyo. Key issues included the antenna specifications and the ACA design. Japan proposed a modified LO system--a photonic hybrid option which replaces warm multiplier assembly. Also discussed was a power generator for whole system with presentation from Canio Dichirico on this. Hasegawa noted that the Japanese had considered how to optimize the OTF capability of the 12m antennas. A simulation result was presented. It was found that tuning antennas to efficiently do OTF results in somewhat different specs from those of the main array; a memo is being written describing the results of the study. Can this requirement be accommodated in parallel with requirement for fast switching on the main array. Another issue on first LO. A possible concern on photonic hybrid has been examined with no outstanding concern. Some higher risk thought to exist by the LO Group; this is still under study. In the Diet, the House of Representatives has passed the 2004 budget, sent to house of councilors. Passage expected by 4 April. Calibration was a major topic of miniALMA Week. The bandpass calibration memo has been submitted and is under review. A chapter on bandpass calibration was added to the Calibration Plan, a rough draft of which has been submitted. Holdaway produced a memo on 250 GHz source counts, based upon new data from MAMBO array; results are optimism about the availability of sources for in-band fast switching for B6 and B7. Chris Wilson asked about the utility of a calibration satellite at mm wavelengths. CA PS for Gemini has interest for putting a source on a satellite. This would serve as an absolute calibration device. It was suggested that this be discussed with Darrel Emerson. This would be useful for holography. It could also have some uses for flux calibration. Hogerheijde noted that a dedicated website will be made for DRSP. He needs to make sure that script will work. DiFrancesco asked how to modify the DRSP. Hogerheijde is the contact for this. Laing is developing some polarization projects for eventual inclusion. The ASAC is considering asking DRSP contributors to supply additional information on the level of calibration accuracy needed for their experiments. Robert reported on SSR activity--meeting tomorrow. Some tests of obs prep system and offline testing. These worked quite well, please examine the reports. Memo underway on data rates. Also under discussion is the amount of work required for the tests. Conway has submitted draft early science configurations on the web, jump frog triangles of configurations. This assumed 172 pads available by the end of 2007, whereas some will not be ready. Configuration 6 will not be possible, some changes on configuration 5. This will have some repercussions on the inner configurations also. Will submit it to almaedm at that point. Eventually plans needed to build this up. Conway also discussed the cycle time of whole array and constraints on the transporter. There is a strawman in the comments on the transporter spec document in the absence of a proposal from science. We will come up with a strawman now that we know the total number of pads. We think a 9 month cycle is good, which has an average of 4 moves every 2.5 days. This will be specified in the antenna movement document which awaits further comment in the almaedm DAR. Conway described the baseline calibration plan he began using monte carlo simulations and kolmogorov turbulence. Then he attacked it analytically in the case of one moved antenna and a single antenna with which its baseline is calibrated. Ocassionally the whole array is calibrated. The question is the balance between these. The biggest problem is getting the z component, as only one hemisphere is being sampled. One finds that the residual phase scales at a strong power of baseline length. Math is analogous to two antennas 1 km apart with a 36 km atmosphere. So one must use short baselines, <1km perhaps 500m. Once array is largest, the calibration needs to be done with the nearest unmoved antenna, probably in night, probably takes one hour. Just takes a few antennas from the larger array and does not cause a large loss of baseline hours. Errors increase as one goes further out. One builds in a guard against systematic error. Is the 65microns on each coordinate or the total. Can afford to have some antennas with larger than this error. Will run tests to show the effect of baseline accuracy on image quality. Also worried about dry path effects owing to altitude effects. ACTION: Wootten get with DTE on satellite. Wilson wrote an email introducing the topic to him. ACTION: CSV plan and canvass. Laing provided the plan to Japanese colleagues. ACTION: John will work on the antenna location plan Lucas--Date change to third Tuesday. 20 Apr Stay constant in local time, change in UT. Respectfully submitted, Al Wootten