The range of angular scales that the array must be sensitive to cannot be accessed with any practical homogeneous array, thus a heterogeneous array is required. The present concept of the ngVLA includes three fundamental subarrays:
- A Main Interferometric Array of 214 x 18 m reflector antennas
- A Short Baseline Array (SBA) of 19 x 6 m reflector antennas
- A Long Baseline Array (LBA) of 30 x 18 m reflector antennas
The main array is distributed to sample a wide range of scales from 10s of meters to 1000 km. A dense core and spiral arms provide high surface brightness sensitivity, with mid-baseline stations enhancing angular resolution.
A short baseline array (SBA) will be sensitive to a portion of the larger angular scales undetected by the main array. The SBA may be combined with 4 18m (main-array) antennas used in a total power mode to completely fill in the central hole in the (u,v)-plane left by the 6m dishes.
A long baseline array (LBA) will add an additional 30 reflector antennas in 10 clusters providing continental scale baselines (BMAX ~ 8860 km). The LBA is designed to sample a broad range of scales for stand-alone sub-array use, as well as for integrated operation with the main array.
The main array will include stations in other locations throughout the state of New Mexico, west Texas, eastern Arizona, and northern Mexico. Long baseline stations are located in Hawaii, Washington, California, Iowa, Massachusetts, New Hampshire, Puerto Rico, the US. Virgin Islands, and Canada.
The ngVLA will have approximately ten times the sensitivity of the VLA and ALMA, continental-scale baselines providing sub-milliarcsecond-resolution, and a dense core on km-scales for high surface brightness sensitivity. Such an array bridges the gap between ALMA, a superb sub-mm array, and the future SKA1, optimized for longer wavelengths.