The NRAO Green Bank Telescope (GBT) is the largest fully-steerable radio telescope in the world that operates at wavelengths as short as a few mm. A large fraction of the observing time on the telescope is used for spectral line work, yet the output is severely limited by the current spectrometer because it does not enable the full capabilities of the front-end receivers. A new spectrometer planned by PI Dan Werthimer and collaborators at the University of California - Berkeley and NRAO will be based on modern Field Programmable Gate Array technology and standardized component hardware to allow simultaneous observation with all 7 dual-polarization feeds of the K-Band (~1-cm) Focal Plane Array (FPA), or all 16 single-polarization feeds of the 3-mm FPA. The 3-GHz instantaneous bandwidth and 32,768 spectral channels of the proposed spectrometer will provide new capabilities in high-resolution and multi-feed spectroscopy, supporting new science priorities for the GBT, including searching for organic molecules in the interstellar medium, measuring fundamental constants through the evolution of the universe, investigating the dynamics of star-forming regions, and surveying for pulsars near the Galactic center.
The new spectrometer is slated to become a key part of the facility instrumentation at the GBT, ensuring open access by astronomers nationwide, including postdoctoral astronomers and students. By providing much higher spectral resolution and mapping efficiency, the developments will also enable a broad array of scientific endeavors, and by utilizing standardized (Berkeley CASPER) hardware the architecture will be amenable to straightforward maintenance and upgrade. Finally, developments from this project will add to the growing library of open-source hardware, software, and gateware available for scientific signal processing applications available to the community. Funding for this work is being provided by NSF's Division of Astronomical Sciences through its Advanced Technologies and Instrumentation program.
The goal of this project is to develop and deploy the VEGAS spectrometer for the National Radio Observatory's 100 meter diameter Green Bank Telescope (GBT). The VEGAS spectrometer is a major new general purpose multibeam instrument, with unprecedented bandwidth and spectral resolution. This new instrument has impressive capabilities, analyzing up to 8 dual polarization beams, bandwidths up to 8 GHz, up to 64 simultaneous spectral windows, up to 4 million channels, and spectral resolutions as fine as 200 Hz. We completed development, deployment, and testing of the VEGAS spectrometer at the GBT telescope. We tested all 29 modes of the instrument, first in the lab, and then worked with the NRAO staff to integrate the instrument to the telescope hardware and software. We carried out the first science observations with the new VEGAS spectrometer. The spectrometer is working well and data quality is excellent.To test the instrument, we observed radio calibrators, pulsars, galactic HI and HII regions, super nova remnants, as well as the galactic center. The new VEGAS instrument, involving a heterogeneous archtecture, combining general purposeFPGA and ADC boards, GPU's and CPU's, is flexible, scalable, and upgradeable, so the archtecture, platform, libraries and software should prove useful for a wide range of real-time radio telescope signal processing applications at many observatories. Several instruments have already spun off of the VEGAS design, including pulsar and SETI instruments, spectral imaging correlators and several other spectrometers. All hardware, gateware and software is open source and available to the community.
