by Gustaaf Van Moorsel last modified Oct 18, 2013 by Amy Mioduszewski

This document summarizes the current observational capabilities of NRAO's Very Long Baseline Array (VLBA) instrument.  It is intended specifically to accompany the NRAO Call for Proposals for observing semester 2013B, with a submission deadline of 2013 February 1, but is also the best source for up-to-date information on VLBA instrumental developments.  This version, as well as the previous version (specific to observing semester 2013A) are available via .

The VLBA is an array of ten 25-m diameter antennas at stations distributed over United States territory (Napier et al. 1994; Napier 1995). It is the first astronomical array dedicated to observations using the technique of Very Long Baseline Interferometry (VLBI), which was pioneered in the 1960s. The VLBA offers (1) in absentia, year-round station and correlator operation; (2) station locations selected to optimize u-v plane coverage; (3) ten observing bands at wavelengths ranging from 90 cm to 3 mm (two stations are not equipped at 3 mm); (4) rapid, automated selection of receivers and of frequencies within a given receiver; and (5) integrated data flow from acquisition to correlation to post-processing. VLBA observations can acquire simultaneous dual circular polarizations from any single receiver, from widely separated frequencies within the 6-cm band, and from receiver pairs at 13/4 cm or 90/50 cm. The VLBA is operated remotely from the Pete V. Domenici Science Operations Center (SOC) in Socorro, New Mexico.

Broad overviews of the kinds of astronomical research possible with the VLBA are presented in the VLBA 10th anniversary proceedings (Romney & Reid 2005), and the conference proceedings edited by Zensus, Taylor, & Wrobel (1998).  Recommended reading for users new to the VLBA includes a "Guide to Using the VLBA", and a short VLBI overview (Walker 1999b).

This document's primary intent is to provide, in concise form, the minimal information needed to formulate technically sound proposals requesting VLBA resources. A secondary aim is to describe some of the subtleties of data reduction and telescope scheduling. It is updated synchronously with the NRAO calls for proposals, or more often when required by major changes.

Requests for information beyond the scope of this document should be directed to the NRAO Helpdesk.