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 subarray is distributed to sample a wide range of scales from tens of meters to ~1068 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 subarray. The SBA may be combined with 4 18 m antennas (from the Main subarray) used in a total power mode to completely fill in the central hole in the (u,v)-plane left by the 6 m dishes.
A long baseline array (LBA) will add an additional 30 reflector antennas located in 10 stations providing continental scale baselines (BMAX ~ 8860 km). The LBA is designed to sample a broad range of scales for stand-alone subarray use, as well as for integrated operation with the Main subarray.
The Main subarray will include stations in locations throughout New Mexico, west Texas, eastern Arizona, and northern Mexico. LBA stations are located in Hawaii, Washington, California, Iowa, West Virginia, 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.