ngVLA Antenna Configuration Reference Design

The next generation Very Large Array (ngVLA) antenna locations have been chosen to accommodate a wide variety of scientific observations, aiming to deliver high sensitivity over ~4 orders of magnitude in resolution with a non-reconfigurable array. The reference design is composed of three subsets distributed over a range of physical scales: a Main Interferometric Array, a Short Baseline Array (SBA) and a Long Baseline Array (LBA). Furthermore, the Main array is composed of 214 x 18 m antennas distributed in three subarrays: a dense Core of diameter 1.3 km for high surface brightness sensitivity, a multi-arm spiral providing up to 36 km baselines called the Plains subarray and a Mid-baseline subarray with baselines up to 1000 km. The SBA is composed of 19 x 6 m closely packed antennas that provide even shorter baselines than are possible in the Core (i.e., shorter than 38 m). Additionally, four of the 18 m antennas from the Main subset will measure total power to fill in the shortest spacings not well-sampled by the 6 m interferometer. The LBA has 30 x 18 m antennas that contribute the intercontinental-scale baselines (~9000 km) needed to achieve resolutions of ~ 0.1 mas. The ngVLA can in principle operate with combinations of different subsets and/or subarrays to optimized the performance depending on the scientific requirements. We use taperability curves, or the change in sensitivity versus resolution, to compare arrays and to understand how efficiently an array can perform at both high and low resolution. Also, we present updated sensitivity calculations based on new performance simulations. The ngVLA is a design and development project of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.