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GBT: The Robert C. Byrd Green Bank Telescope

Link to GBT Web site

I. General project/facility description

  1. Overview of the facility/project
    The Robert C. Byrd Green Bank Telescope is a 100 meter diameter telescope with offset optics and active surface compensation. It is designed to cover three decades of frequency from approximately 100 MHz to 115 GHz. It is the largest fully-steerable telescope in the world, with access to 85% of the celestial sphere. Its offset optics provide a very clean main diffraction beam with low sidelobes. It is an extremely versatile facility, capable of unique science from meter to millimeter wavelengths.

    Green Bank was the initial site of the National Radio Astronomy Observatory, with construction commencing in the late 1950s. Principal telescopes at the facility have included the 300 Foot (91 m) Telescope, the 140 Foot (43 m) Telescope, the Green Bank Interferometer, and now the GBT. Telescopes presently in operation on the site include the GBT, the 85-3 pulsar monitoring telescope, the 45-Foot telescope now in use for the Solar Radio Burst Spectrometer project, and the 40 Foot Educational Telescope. The Observatory is presently considering a project to recommission the 140 Foot Telescope for contract use by an external group. The Green Bank Interferometer and the 20 Meter Telescope (formerly operated for the US Naval Observatory) are currently dormant but could be reactivated if needed. The site also operates the Green Bank Science Center, a new facility housing classrooms, an auditorium, and exhibits on the science and history of radio astronomy. An active Education and Public Outreach program is run by the staff of the Science Center, including site tours, educational programs for K-12 and undergraduate students, and summer training workshops.

  2. Managing institution and organization
    The Green Bank Telescope and Green Bank Operations are a part of the National Radio Astronomy Observatory, a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

  3. Funding source(s)
    Major funding for Green Bank Operations derives from AUI's cooperative agreement with the NSF. Occasionally, additional funding has been obtained through NSF and NASA grants, or through contracts with other entities to perform a service or operate a telescope. These external grants and contracts are typically small in comparison with cooperative agreement funds.

  4. Construction history and cost
    The GBT replaces the 300-foot telescope which collapsed in 1988. In less than a year, AUI submitted a proposal to NSF for the replacement telescope. GBT construction was included in the Emergency Supplemental Appropriations bill passed in 1989 (this item in the NSF budget became known as the MREFC line). A construction contract for $55M was let to RSI in 1990. "First Light" observation of the pulsar PSR 1140+223 occurred in Aug 2000 about the time of the formal dedication. Commissioning tests began in Feb 2001 with the first early science observations demonstrating the first bistatic (Arecibo-GBT) radar of Venus a month later. Final acceptance of the GBT from the contractor (by this time Lockheed-Martin) occurred in Sept 2001. Full scientific operations were achieved (>50% time scheduled for astronomy) in Oct 2003.

    Total construction cost of the project (1990 dollars): $79M (includes $75M for original construction + $4M for the arbitration award)

  5. Operational history and cost
    The GBT began early scientific operation in the spring of 2001 while commissioning was still underway. For the following two years, science and commissioning activities were interspersed. Routine scientific operation using over 50% of total telescope time was achieved by the Fall of 2003.

    The total budget for Green Bank Operations (including the Science Center) was $10.3M in FY2004.

II. Technical details

  1. Specifics of telescope/instrument
    GBT Antenna Specifications and Performance as of end 2004
    Telescope Diameter100 m (effective)
    Optics110 m x 100 m section of a 208 m parent parabola
    Offaxis feed; Prime and Gregorian foci
    Elevation Limits5 - 95
    Slew rates40/min azimuth, 20/min elevation
    Main reflectorActive surface of 2004 panels, 2209 actuators
    Surface RMS350-400 m ;   avg of individual panels: 68 m
    FWHM beamwidth740/ν(GHz) arcsec

    A suite of low noise receivers provide almost complete frequency coverage from 290 MHz to 50 GHz. A W-band receiver covering 68-92 GHz is under development. The 64-pixel Penn Array Bolometer camera operating in the 80-100 GHz range will be commissioned in Fall 2005.

    A set of spectrometers provide spectroscopic and pulsar capabilities.

  2. New capabilities anticipated/planned in next 5-10 years
    Near-term capabilities (i.e., within next ~3 years):

    Longer term system improvements:
    Continuing investments of a small fraction of the total capital and operational investment in the GBT promise to deliver increases in effective data throughput on the GBT by factors of 100 to 1000. The most promising developments include:

III. User profile

  1. % of "open skies" time
    100% of science time on the GBT is "open skies." All observing proposals are reviewed by independent and anonymous referees and are selected on scientific merit, without regard to the affiliation of the proposers.

  2. Institutional affiliations of users
    See the NRAO Observing Summary document for 2003, p. 13ff.

  3. Student access, involvement, usage
    Students are encouraged to use the GBT through the GBT Student Support Program. This program provides students with one-year stipends of up to $32,000, with an additional $3000 available for computer equipment and travel expenses. The intent of the program is to foster students interested in radio astronomy, in general, and the GBT, in particular. To be eligible for the awards, students must first obtain observing time through the regular proposal process, then they may compete for stipends.

    For several years, the NRAO has supported a University-built Instrumentation program which funds unique instrumentation built at university labs for use on the GBT. An explicit motivation of this program is to support and invigorate university instrumentation laboratories and to foster the training of graduate students in instrument development. Current projects in this program include the Penn Array camera and the Caltech Continuum Backend.

    Green Bank Operations has for many years supported co-op and predoctoral student programs. Together with NAIC, Green Bank Operations holds a biannual summer school for single dish radio astronomy which also trains students and postdocs in the technical aspects of radio astronomy.

    In 2003, 3% of total observing time on the GBT was used by students.

IV. Science Overview

  1. Current forefront scientific programs

V. Education/Outreach activities

  1. Visitor facility
    The NRAO operates the new Green Bank Science Center, a 25,000 sq ft facility, opened in May 2003. The facility has a large exhibit hall containing instructional displays and hands-on demonstrations of the science and history of radio astronomy. The exhibits were professionally designed and were funded by an NSF informal education grant. The Science Center also contains three classrooms, a computer lab, a 150-seat auditorium, a gift shop, and a caf.

    The facility is open seven days a week from the end of May through October, and five days a week (Wednesday through Sunday) for the remainder of the year. It serves walk-in tourists and the general public as well as arranged school field trips. Tourists may view a 10 minute, professionally-made film on the GBT and the science of radio astronomy in the auditorium. Guided tours of the site on diesel tour buses are also offered throughout the day. Visitors are also welcomed to walk or bicycle about the site. Special programs (e.g., star parties, movies) are also scheduled regularly.

    To support overnight visits by student groups, a new bunkhouse-style dormitory was built as part of the Science Center project. The facility has bed and bath accommodations for 32 girls and 32 boys, with private rooms for supervisors.

  2. Student programs
    The EPO staff at Green Bank offer programs to K-12 students and undergraduates that include overnight stays and hands-on research activities using the 40 Foot Educational Telescope. The students are given projects to measure continuum or HI line fluxes, and are encouraged to devise their observing techniques, control the telescope, make the measurements, and interpret the results. Shorter activities are also available for school groups visiting on day trips.

    Most of the K-12 groups come from West Virginia, Virginia, Pennsylvania, and other parts of Appalachia. The undergraduate groups typically come from colleges and universities in the region, although groups from as far away as Michigan are common.

    The EPO staff has the goal of having every West Virginia school student visit the Observatory at least once before they graduate from high school.

  3. Other (as apply)
    The Green Bank EPO staff in collaboration with West Virginia University, has for many years conducted a intensive teacher training course known as RARECATS. The course is held over a two-week period in the summer, with a follow-up session the next summer. The teachers attend lectures from staff astronomers and conduct experiments on the 40 Foot Telescope. The objective of the school is to give the teachers a real research experience in which they must go through the scientific process of experiment design, data acquisition, and data interpretation. Continuation of this program is subject to funding.

    The EPO staff also host two Chautauqua courses each summer in Green Bank, a Hands-On Universe workshop, and co-host the NASA/NRAO Astronomy Institute. The EPO program at Green Bank has a long collaboration with the National Youth Science Camp (NYSC), which includes an annual program component conducted at the Observatory. In the summer of 2005, the Observatory is hosting the West Virginia Governor's Academy for Math and Science in collaboration with the NYSC.

VI. Documentation/website URLs

  1. URL of facility website
  2. URL of EPO website

  3. URL(s) of any brief overviews of project/facility
    See facility page.
  4. URL(s) of miscellaneous documentation
    See facility page.

This page created and maintained for the RMSPG by Martha Haynes Last modified: Thurs Feb 10 2005 by Phil Jewell.