One of the most difficult tasks will be the IF processing and phase tracking system, which defines interfaces for receivers and correlators, and hence requires excellent coordination. If the site is in South America, it may be useful to get help during the study phase from the European Southern Observatory, and some sharing of existing ESO infrastructure, transport, etc., in the initial period. The dishes should be simple and robust, and able to keep their mm-quality surface without any active corrections. The goal should be to have strong antennas which can survive in the outdoors, without astrodomes, and without active optics. Because of the small beamwidths at mm wavelengths, strong efforts should be made to improve pointing and focussing accuracy.
Thermal effects dominate the precision of pointing and focussing.
The study should be aimed at keeping pointing precision and focus stability even when part of the antenna structure is in sunlight, and part in shadow. The telescope pointing deserves strong engineering efforts . It may be desireable, in the late 1990's, to try out one or more prototypes of improved antennas with the IRAM array before starting a production run for a next-generation mm array. These prototypes might then be re-integrated into the new instrument when it is built. Receivers should be designed to be tunerless, maintainence-free, have a minimum of moving parts, and require no helium filling.