The VLBA: A Telescope Moving Forward
Abstract
The NSF Senior Review recommended that operational funding partners be found for the Very Long Baseline Array (VLBA), but also commented favorably on scientific prospects for the VLBA. NRAO is realizing those prospects through a substantial increase in sensitivity of the VLBA, the only full-time milliarcsecond imaging telescope. With partnerships in hand, and recent exciting results such as determination of a higher Milky Way mass (Reid et al. 2009, ApJ, 700, 137), and images of flaring gamma-ray sources detected by Fermi, the VLBA is poised to offer new science capabilities by 2011. Examples of programs enabled by the VLBA Sensitivity Upgrade include three-dimensional maps of star-forming regions, probes of gamma-ray emission mechanisms in pulsars, and census of supernova-remnant populations in starburst galaxies.
The near-term focus is on a fourfold increase in continuum sensitivity, achieved by bandwidth expansion from 32 MHz to 512 MHz per polarization; a longer-term goal is to approach 8 GHz per polarization, the same as EVLA and ALMA. The first required element, adaptation of the DiFX software correlator developed at Swinburne University (Deller, et al. 2007, PASP, 119, 318), is in place; procurement of additional processors will permit the expanded bandwidth to be processed. DiFX offers much improved spectral and temporal resolution and adds new pulsar-processing capabilities; further functionality nearing deployment includes the ability to image hundreds of fields within the antenna primary beam simultaneously, with minimal processing overhead. By early 2011, a new digital backend (DBE) will replace the original analog baseband hardware, sampling intermediate-frequency signals directly, and providing both a polyphase filterbank and a digital downconverter. DBE output samples will be formatted in industry-standard 10-Gigabit Ethernet packets. The new Mark 5C recording system will record the packet payloads, and is optimized for direct access by a software correlator.- Publication:
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American Astronomical Society Meeting Abstracts #215
- Pub Date:
- January 2010
- Bibcode:
- 2010AAS...21544207U