Dear colleague,
On June 25 and 26, representatives of the U.S. and European millimeter communities met to discuss the possibility of joining together to build a larger millimeter and submillimeter array than either group could by themselves. The discussions went well and a decision was made to conduct detailed discussions about what form such a project would take. The goal is to agree as rapidly as possible on the project so we build the joint array as quickly as possible and not slow down the momentum which the U.S. has built up behind the MMA project.

The general outline which made sense in the initial meeting was a single project on the 5000 meter Llano de Chajnantor site which previously had been chosen for the MMA. Baselines up to 10km and a frequency range including the submillimeter were part of the discussion. The project would a 50/50 even split in construction costs and operation and would be about twice the size of the MMA project by itself. The major unresolved issue in the description of the project is the number, properties and size or sizes of the the antennas. The European emphasis has been on collecting area, the U.S. project has emphasized imaging.

Two options for resolving this issue came out of the meeting. In broad outline, the options can be summarized below,

Option 1)

M antennas of 8 m diameter,

- pointing accuracy adequate up to 800 GHz (i.e. 1")

- surface accuracy 25 microns

N antennas of 15 m diameter,

- pointing accuracy adequate up to 350 GHz (i.e. 1.5")

- surface accuracy 25 to 30 microns where M is about 40, an N is between 25 and 35, depending on the final cost equations.

Option 2)

L antennas of 12 m diameter,

- pointing accuracy adequate up to 650 GHz (i.e. 1")

- surface accuracy 25 microns L of order 50 to 60, depending in the final cost equations.

All of these numbers are subject to revision as the cost equations improve. Option 1) is a combination of the antenna sizes favored by the current U.S. and European concepts before the meeting. The European design draws strongly on the IRAM experience with antennas of this size. The 12 meter design from option 2) would supposedly come from scaling down the European antenna or scaling up the U.S design. We would like, at this time, feedback from the community on their initial thoughts on the joint project and the two options in particular. Science is the number one consideration here. However, both groups may need a fallback position if the funding from the other side does not materialize. Also time is of the essense. We cannot afford to study this question for very long. We need a strategy which will allow us to proceed quickly with the project. Also the options described above are not set in stone, so we would also like to hear other ideas as well as what the boundaries should be on an acceptable option. Please try to relate the comments to your scientific interests and give examples of how you would make use of the instrument.

So please send your comments to me at mmalsa@nrao.edu

We will keep you up-to-date as the situation develops.

---Frazer Owen MMA Project Scientist