20-meter Telescope

The 20-meter telescope is used for a combination of educational and research projects.

Run remotely by members of the SKYNET program, an astronomy education project based at the University of North Carolina in Chapel Hill, it is in regular use for educational activities around the U.S. and around the world. Via Internet remote control, students use the 20-meter to observe the invisible Universe from their classrooms.

Anyone may apply to use it through the UNC Skynet program.

A project with Virginia Tech and West Virginia University has used the 20-meter to search for the mysterious “fast radio bursts”, flashes of radio energy that happen seemingly at random spots in the sky at random times. Many observatories, as well as Green Bank, are trying to gather more information to understand what is making these signals.

Learn more about the 20-meter telescope.


The 20-meter telescope arrived as a guest at our site in Green Bank, West Virginia in 1994.  The telescope was built by RSI, funded by the US Naval Observatory (USNO) as part of their Earth orientation observing programs.

Engineers in Green Bank built its receiver and installed it on January 11, 1995. The 20-meter observed with other telescopes to test its systems during the next few months, but had to give up some of its parts to help a twin 20-meter in Hawaii. By October 1995, the 20-meter was in regular operation by the USNO.

The USNO uses antennas around the world to measure small wobbling motions of the Earth’s polar axis and irregularities in the Earth’s rate of rotation with reference to positions of quasars (distant bright explosions in nuclei of galaxies). Quasars are the most distant point-like radio sources known, and therefore form a good set of stable reference points. This telescope network is part of the the International Earth Rotation Service (IERS) and supplies data needed for high accuracy world-wide navigation systems.

The data are also used for studies of continental drift and of atmospheric and oceanic currents, in collaboration with the NASA Geodetic VLBI program. Prior to the completion of the 20-meter, these geodetic VLBI experiments had been using telescope 85-3, part of the Green Bank Interferometer.

The USNO shut down their use of the 20-meter in June 2000 due to funding cutbacks. Although the Green Bank 20-meter is no longer used for the USNO project, USNO monitoring  of Earth rotation and motions continues using the NRAO VLBA antenna array as well as telescopes in Hawaii and Germany.

In 2008, an L-band frequency array receiver feed, destined for use on the Robert C. Byrd Green Bank Telescope, was installed and tested on the 20-meter. It successfully observed the radio emissions around the famous Cygnus X-1 black hole complex.

The 20-meter was refurbished in 2012 as the first radio telescope in the SkyNet robotic telescope network project run out of the University of North Carolina, Chapel Hill.

Old receivers formerly used on the 140-foot telescope were revived and adapted for use on the 20-meter, providing receivers sensitive to 1.3-1.8 GHz, and 8-10 GHz.

Stats for the 20-meter Telescope

Height: 85 feet
Weight: 150 tons
Receivers: 1.3 to 1.8 GHz and 8 to 10 GHz at the prime focus
Slew Speed: 2 degrees per second, each axis.
Surface Accuracy: 0.8 mm rms.
Focal Ratio (F/D): 0.43
Geodetic Position: 38 26 12.661 N.Lat, 79 49 31.865 W.Long.