The Next Generation VLA (NGVLA) aims to provide excellent image fidelity for a broad spectrum of science cases. At the same time, in order to keep construction and operations cost as low as possible, the NGVLA antennas will not be reconfigurable. The NGVLA reference design calls for 214 18m diameter antennas distributed in a spiral pattern with baselines out to ~1,000 km. A 1-km diameter “core” contains 94 of the 214 antennas, with baselines as short as 38m (set by antenna clearance requirements). Roughly 30% of identified NGVLA science cases require measuring larger spatial structures than the NGVLA main array will measure, thus shorter spacings are needed.
To meet this need, an NGVLA Short Baseline Array (SBA) has been designed and incorporated into the NGVLA reference design. The SBA consists of 19 6m antennas with baselines as short as 11m. In order to provide information on yet larger spatial scales, the SBA also includes four 18m total power antennas.
This poster describes the SBA requirements and design, including recent modifications. It also presents an evaluation of the SBA in the context of a notional observing program, and the results of improved simulations quantifying the ability of the SBA to recover spatial scales much larger than the field of view of one pointing of the 18-m antennas in the ngVLA core.