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Introduction to the GBT

The World's Premiere Filled-Aperture Radio Telescope



The GBT is the world’s premiere single-dish radio telescope operating at meter to millimeter wavelengths. Its enormous 100-meter diameter collecting area, unblocked aperture, and excellent surface accuracy provide unprecedented sensitivity across the telescope's full 0.1 - 116 GHz (3.0m – 2.6mm) operating range.

The GBT’s filled aperture has comparable collecting area and sensitivity to ALMA and the EVLA, but with the image brought to a single focal plane. This provides the GBT with extraordinary sensitivity to extended, low surface-brightness objects such as diffuse molecular clouds or Sunyaev-Zel’dovich distortions of the cosmic microwave background (CMB), as well as high sensitivity to point-source radiators such as pulsars.

The single focal plane is ideal for rapid, wide-field imaging systems – cameras. The GBT thus serves as the wide-field imaging complement to ALMA and the EVLA. The single focal plane also provides an accessible development platform and allows much of the advanced, instrumentation to be provided by university-based laboratory groups. The GBT’s high sensitivity imaging and point-source capabilities enable a large and varied program of key science projects. In addition, the GBT often joins the VLBA for interferometry observations to provide a critical threshold of sensitivity for a number of important projects, including, for example, the megamaser cosmology experiment.

A unique and powerful telescope that is used by hundreds of scientists each year, the GBT is fully steerable, and 85% of the entire celestial sphere is accessible to it. Its operation is highly efficient, and it is used for astronomy ~ 6500 hours per year, with 2000-3000 hours per year going to high frequency science. Part of the scientific strength of the GBT is its flexibility and ease of use, allowing for rapid response to new scientific ideas. It is scheduled dynamically to match project needs to the available weather. The GBT is also readily reconfigured with new and experimental hardware, adopting the best technology for any scientific pursuit. Facilities of the Green Bank site are also used for other scientific research, as well as for an extensive array of programs in education and public outreach, and for the training of science and engineering students and teachers. The complex is a large site with laboratories, utilities and support facilities that makes it an attractive location for staging a variety of research experiments. In addition, because of the National Radio Quiet Zone and the West Virginia Radio Astronomy Zone it is uniquely protected from many forms of man-made radio frequency interference.

The GBT was designed to allow ready upgrades and changes to all aspects of its hardware and software. A specialty (or principle investigator-driven) instrument can be installed on the telescope with relative ease, making it feasible for an individual or group of researchers to outfit the telescope to meet their particular science goals. The GBT also has a vigorous development program in collaboration with college and university groups to take advantage of the latest technology and provide our user community with a constantly improving facility. In concert with the community, development projects for the GBT will continue through the coming decade and have already led to important discoveries in a number of areas, from discovering the most massive neutron star yet known, which has had great impact on our understanding of physical equations of state in dense matter, through making the highest resolution, most sensitive images of the Sunyaev-Zel’dovich effect yet known, to provide insight into the formation of clusters of galaxies.

Over the next 10-20 years the GBT will contribute to our understanding in areas as diverse as the detection of gravity waves, the formation of stars, galaxies and galaxy clusters, the origin of life, the composition of the planets and their satellites, and the scientific principles that govern the Universe. The telescope’s strength is its flexibility, sensitivity, and sky coverage, allowing for rapid response to new and innovative scientific ideas over three decades of frequency. Although the most important science may come from projects not yet conceived, there are a number of key science areas in which the GBT will excel over the coming decade.