Large MM and Sub-MM Array Project and International Collaboration

The Large Millimeter and Submillimeter Array(LMSA)is a high priority project for the future large-scale ground-based astronomical facility of Jpapn.The LMSA is an interferometer array consisting of fifty 10m antennas covering a frequency range from 80GHz to 890GHz.To achieve efficient operation at the highest frequencies, the array will be located on a high, dry, and flat site in the eastern Atacama Desert of northern Chile.With a 10-km maximum baseline at 350 GHz the LMSA will provide 10 milli-arcsecond resolution which has never been achieved with existing millimeter and submillimeter telescopes.The main scientific tragets of LMSA are to reveal the fundamental process of planet fo rmation, and the formation and evolution of galaxies.The LMSA is also expected to provide a very powerful tool in the researches of cosmology, active galactic nuclei, star formation, interstellar matter, and planetary science.It is being proposed to realize more powerful array and cost saving by merging the LMSA with European LSA, and U. S.MMA projects.The main motivation of the proposal is:all three projects identified the same area in Northern Chile as their potential site, and U.S.and European communit ies also recognize the importance of submillimeter performance which has been the main target of the LMSA.If a huge array of hundred 10-12 m antennas is realized, the collect ing area and number of baselines are 2.5 and 4.0 times larger than the original LMSA, respectively.