This document summarizes the current observational capabilities of NRAO's
Very Long Baseline Array (VLBA) instrument. 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 
-
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 or from receiver pairs at 13/4 cm or 90/50 cm. The VLBA is
operated remotely from the Pete V. Domenici Science Operations Center
(DSOC, formerly known the Array Operations Center) in Socorro, New Mexico.
Broad overviews of the kinds of astronomical research possible with the VLBA are presented in the conference proceedings edited by Zensus, Taylor, & Wrobel (1998), and the VLBA 10th anniversary proceedings (Romney & Reid 2005). Recommended reading for users new to the VLBA includes a short VLBI overview (Walker 1999b) and a short guide for novice users of the VLBA (Ulvestad 2004).
This document's primary intent is to provide, in concise form, the minimal information needed to formulate technically sound proposals requesting VLBA resources. Secondary aims are to describe some of the subtleties of data reduction and telescope scheduling, and to list relevant software and documentation. It is updated synchronously with the NRAO calls for proposals, or more often when required by major changes, and is available through http://www.vlba.nrao.edu/astro/obstatus/current/.
Requests for information beyond the scope of this document should be directed to the NRAO Helpdesk, at http://help.nrao.edu/.