Plan for an Enhanced ALMA 12 June 2000 Japanese members of ASAC Japan will participate in an enhanced ALMA project as an equal partner as the US and European sides by bearing 1/3rd of the project. To realize the project, we will ask the budgets of its design for FY2001 (which starts from 2001 April) to the government in 2000 June and of its construction for FY2002 to FY2008 in 2001 June. Our plan is that construction of the Japanese portion finishs in FY2008, adjustments with the US and European portions are made in FY2009 and FY2010, and full operation for astronomical observations starts in FY2010. However the detailed schedule will be decided under nagotiation with the US and Europe and we keep in step with the other partners. Dr R.L.Brown asked ASAC prioritizing the plan of an enhanced ALMA on May 12 to send a report to AEC until June 23. According to this seeking, we have made the following plan for the enhanced ALMA on the basis of science return and construction cost and present it here to ASAC for discussion. Boundary conditions considered for the plan is .that the total cost or "value" of the enhanced ALMA is $552M/2 x 3 = $828M, .that the costs (values) of the parts follow the estimation and equations in "PLANNING FOR JAPANESE PARTICIPATION IN ALMA" (R.L.Brown, 12 May 2000) for simplicity, except the second generation correlator whose cost has been estimated by ourselves. Since the cost of antennas is the biggest, its unit price influences the total plan of the project largely. When the cost of an antenna is fixed, we would have to re-consider the plan. Plan for an Enhanced ALMA 1) Antennas A number of 12-m antennas is 78. Each antenna should have enough capability for submillimeter observations. Science merits: Sensitivity of the array is increased by increasing the number from 64. A compact array of seven 6 - 8m antennas is added. The value of a small antenna should be equal to that of a 12-m antenna. Science merits: Since the minimum anntena spacing becomes shorter to be 8 - 11m, capability of the array for extended sources is improved, especially for shorter wavelengths. Total cost of all antennas = $20M + $3.0M x (78 + 7) = $275M Japan will bear 1/3rd of the total number 85 of the antennas. 2) Receivers and LO Bands 3, 6, 7, 9 which have been given first priority in ASAC in March are important. In addition to these bands, bands 8 and 10 are also important and should be given high priority. Science merits: (see attached appendix) .Band 8 includes important lines of CO(J=4-3;460GHz), CI(J-1-0;492GHz), CS(J=10-9; 489GHz) et al. and thus is useful for study of interstellar matter and to see the cores of star forming clouds and inner 10 AU of protoplanetary disks. .Band 10 includes extremely high excited lines such as CO(J=7-6;807GHz), HCO+(J=9-8;802GHz,J=10-9;892GHz), HCN(J=9-8;797GHz,J=10-9;885GHz) which are good tracers of high temperature and high density gas, and CI(J=2-1;809GHz). The band could detect redshifted strong CII from galaxies at z = 1.1 - 1.4. In addition, the band is useful to observe strong thermal emission from heated dusts which is quite important and useful to observe galactic regions of star and planet formation and external galaxies. .By increasing the number of receiver bands to be six, many excited lines of same molecules are observable, contributing accurate determination of physical and chemical states of galactic and extragalactic molecular clouds. Total cost of receivers = [$700k + $200k x 6] x (78 + 7) = $161.5M Total cost of LO system = [$200k + $100k x 6] x (78 + 7) = $68.0M Japan will bear two of the six bands. Since band 10 needs technical development of THz SIS heterodyne reveivers, Japan may take charge of the band. 3) Correlator NRAO will construct the first correlator which can correlate signals from 32 antennas. In addition to the correlator, Japan and Europe, collaborating each other, will develope and construct the second generation correlator which can correlate 125 kch/IF of signals from all the antennas 85. Science merits: .The second generation correlator can treat all the antennas. .The correlator can improve the sensitivity by corresponding to multi- bits of the A/D converters. .Its high capability for spectroscopy can observe many spectral lines in the broad frequency band simultaneously. .Such high spectral capability may make serendipitous discoveries which open new world in astronomy. Cost of the first correlator (filter+XF,32 anntennas,2GHzx8IF,4kch/IF) = $7M (from correlator PDR) Cost of the second generation correlator (FX,85 antennas,4GHzx4IF,125kch/IF) = $44M (Cost of A/D converters will be included in the following Backend Subsystem) 4) Others According to the suggestion in "PLANNING FOR JAPANESE PARTICIPATION IN ALMA" (R.L.Brown, 12 May 2000), we bring to the enhanced ALMA .additional $30M for site development, .additional money for backend subsystem, corresponding to the increased number of antennas, .increasing contributions for management, system engineering & integration, and science support by Japan by 50%, .additional contribution of $10M for computing subsystem by Japan, as follows, ALMA E-ALMA Management $24.6M + 12.3 = $ 36.9M Site Development 77.9 + 30 = 107.9 Backend Subsystem(IF,A/D) 32.9 + 32.9*(85-64)/64 = 43.7 Computing Subsystem 30.7 + 10 = 40.7 System Engin & Integration 21.3 + 10.7 = 32.0 Science Support 7.0 + 3.5 = 10.5 total 271.7 { Total cost (value) of the enhanced ALMA Antennas $ 275 M Receivers 161.5 LO subsystem 68.0 Correlator 7 (first generation; NRAO) 44 (second generation; Japan & Europe) Others 271.7 Total 827.2M =======================================================================