ALMA Liaison Group Issues

The possibility of a contribution of Japan to the ALMA project has received strong and positive support from the ASAC. Such a contribution will make ALMA the largest international collaboration in astronomy and enhance the project in a number of important ways. It will increase the sensitivity of the array and add new technical capabilities. If this collaboration is achieved, Japan will have an equal partnership in the ALMA project with America and Europe and share the infrastructure and running costs. At this point, it seems that the basic contribution of Japan to the ALMA project will be to add 12-meter antennas to the 64 x 12-meter antennas agreed to by the current collaboration. This greater collecting area will result in a better sensitivity (or observing speed), close to the original goal of a $\rm 10,000 \, m^2$ array. This improved sensitivity will compensate the need to share the observing time with a greater number of users. Further contributions of Japan to an enhanced ALMA project are related to specific technical developments, including the participation in the future correlator, construction of the highest frequency receivers, or the photonic LO system. It is too early for the ASAC to prioritize the importance of these possible contributions; further discussion is needed. It is clear that the contribution of Japan to the ALMA project could also open new perspectives for the project. In particular, the possibility to add to the project a compact array of smaller, high accuracy dishes would be a most interesting addition. It would improve the image quality for extended sources and the performance at the highest frequencies. This possibility should therefore be discussed again when the Japanese participation is confirmed.