100m Robert C. Byrd Green Bank Telescope
The Robert C. Byrd Green Bank Telescope, or GBT, is the world’s premiere single-dish radio telescope operating at meter to millimeter wavelengths. Its enormous 100-meter diameter collecting area, its unblocked aperture, and its excellent surface accuracy provide unprecedented sensitivity across the telescope’s full 0.1 – 116 GHz (3.0m – 2.6mm) operating range.
The single focal plane is ideal for rapid, wide-field imaging systems – cameras. Because the GBT has access to 85% of the celestial sphere, it serves as the wide-field imaging complement to ALMA and the EVLA. Its operation is highly efficient, and it is used for observations about 6500 hours every year, with 2000-3000 hours per year available 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 Observatory are also used for other scientific research, for many programs in education and public outreach, and for training students and teachers.
Quick Facts about the GBT:
- The GBT is running observations roughly 6,500 hours each year, more than any other observatory
- For each hour of time available for science on the GBT, roughly 3-4 hours are requested
- More than 600 individual scientists and students proposed to use the GBT within the past year
- More than $25,000,000 has been invested in the GBT in the past five years by colleges, universities, the NSF, and the state of West Virginia
- The surface of the GBT is perfectly smooth to a noise level of 260 microns (5 human hairs)
- The pointing accuracy of the GBT is 2 arc seconds, able to resolve a quarter at 3 miles
- The GBT weighs almost 17 million pounds and stands over 485 feet above ground level
- The GBT’s collecting area is 2.34 acres and its diameter is 300 feet
- The GBT operates 24 hours/day, 362 days/year
- The operational funding provided by the NSF is approximately 0.1% of the NSF astronomy budget
- Coordinates: Latitude: 38°25’59.236″ North (NAD83); Longitude: 79°50’23.406″ West (NAD83); Track Elevation: 807.43 m (NAVD88)
- Optics: 110 m x 100 m unblocked section of a 208 m parent paraboloid; Offaxis feed arm
- Telescope Diameter: 100 m (effective)
- Available Foci: Prime and Gregorian; f/D (prime) = 0.29 (referred to 208 m parent parabola); f/D (prime) = 0.6 (referred to 100 m effective parabola); f/D (Gregorian) = 1.9 (referred to 100 m effective aperture)
- Receiver mounts: Prime: Retractable boom with Focus-Rotation Mount; Gregorian: Rotating turret with 8 receiver bays
- Subreflector: 8-m reflector with Stewart Platform (6 degrees of freedom)
- Main Reflector: 2004 actuated panels (2209 actuators); Average intra-panel RMS 68 μm
- FWHM Beamwidth: Gregorian Feed: ~ 12.60/fGHz arcmin; Prime Focus: ~ 13.01/fGHz arcmin (see Section 4.1.1 of the Observer’s Handbook)
- Elevation Limits: Lower limit: 5 degrees; Upper limit: ~ 90 degrees
- Declination Range: Lower limit: ~−46 degrees; Upper limit: 90 degrees
- Slew Rates: Azimuth: 35.2 degrees/min; Elevation: 17.6 degrees/min
- Surface RMS: Passive surface: 450μm at 45° elevation, worse elsewhere;
- Active surface: ~250μm, under benign night-time conditions
- Pointing accuracy: 1σ values from 2-D data; 5″ blind; 2.2″ offset
Click any image for a larger view.
Green Bank Interferometer
In the 1960s, we wanted to build an array of radio telescopes called an interferometer that simulates a larger telescope from the combined observations of strategically-aligned smaller ones. When the waves of these separated telescopes are combined, the signals get stronger and the noise flattens out, creating sharper views of radio objects.
However, before such a large-scale project could be funded, we needed to prove our design’s hardiness and our ability to operate it.
From 1959 in Green Bank, we had been running a successful and busy 85-foot telescope, called the Tatel Telescope, that we bought as a kit from Blaw-Knox Corporation. Blaw-Knox was still making these kits in 1963 when we ordered another 85-footer from them to create a two-telescope observing system.
By February of 1964, we had assembled this near-twin 85-foot radio telescope that we named the 85-2. The 85-2 differed slightly from the Tatel in that it had 80 14-ply truck tires permanently mounted to its frame. Using a D-7 Caterpillar and an Army surplus aircraft towing tractor, we could haul the 85-2 closer or farther away from the static Tatel to change the pair’s combined resolution and sensitivity.
In anticipation of our new movable arrival, we built a mile and a half-long track leading away from the Tatel. We placed the 85-2 at the end of the new track for maximum distance and mounted six staging stations at 1000-ft intervals along the track. Each station had three piers for stability and sockets for data and power lines that ran the length of the track, some buried, some suspended above on trays.
Cabling between the 85-2 and the 85-foot Tatel took several months, and, with the first digital autocorrelator to combine their observations, the two finally became a working interferometer on June 1, 1964. The interference patterns of the telescopes’ combined radio wave observations told astronomers about position, size, and strength of objects in space.
Renamed the Green Bank Interferometer, this pair’s interference (fringe) patterns were very good, showing astronomers the periodic changes in radio signals from objects that dimmed and brightened over time. Within the first year of GBI observations, the major astronomy report from the National Academy of Sciences recommended the immediate funding and building of a large-scale radio telescope array as a national science facility. We began experiments and discussing designs for what would become that national facility, the Very Large Array in New Mexico.
We built for the GBI a new control room and added a third 85-foot Blaw-Knox telescope to the middle of the interferometer track in spring of 1967, greatly increasing the sensitivity of the Green Bank Interferometer. The 85-3, too, had truck tires mounted on either side, and we used it to test multiple baselines – but still only in one, short direction, running roughly northeast to southwest. For a true test of a high-resolution array, we needed a telescope located far outside of that track.
Therefore, that year, a fourth portable telescope was added to the Green Bank Interferometer. The dish of this portable kit telescope was half the size of the others, 42 feet. This unique telescope could be dismantled and hauled away on the truck that also ran its control desk and motorized mount.
The 42-foot telescope was hauled first to a location 8 miles from its larger siblings. It later was relocated to a site 11 miles north-northeast, a mountaintop called Spencer Ridge. (The distance is the same as an arm of the Y-shaped VLA, still under design at the time.) Finally, it was sited on a ridge in Huntersville, West Virginia, 26 miles from Green Bank, the same distance of the longest baseline of the VLA.
Its observations were wirelessly transmitted as a microwave data link down the mountains to a receiver that sent the signal into the autocorrelator, still in the little building along the GBI track.
By 1972, the aging surface of the 42-foot portable was too inaccurate for our increasing research needs, and the unique telescope package was given to Cornell for interferometer work at its Arecibo observatory in Puerto Rico.
A new, 45-foot portable replaced the outgoing 42-foot in 1973 and served through 1983 on the Huntersville mountaintop. It was brought back to the Green Bank site as a stand-alone telescope, still in use, but now as a solar radio telescope.
A new 46-foot portable dish telescope was placed on Point Mountain to complete the VLA test work. In 1988, with the VLA nearly a decade into its reign as the best interferometer on Earth, the 46-foot was given to the NOAA, moved to Fortaleza, Brazil in 1991, and served as an element in their Earth-mapping VLBI project.
The GBI continued doing important scientific observations into the 21st century.
The Green Bank Interferometer was not solely a VLA testbed. It was a fully-functioning, state-of-the-art interferometer on its own. Most notably, in mid-February of 1974, the GBI discovered an intense and point-like source of radio waves coming from the heart of our Milky Way Galaxy. Named Sagittarius A*, this incredibly compact object was soon determined to be a supermassive black hole. Until 1978, the GBI’s detailed views were used for studying fine structure in known radio objects. The GBI completed the first radio measurement that confirmed, to high accuracy, Einstein’s prediction of the bending of light (i.e. any electromagnetic radiation) near a massive body, commonly called Einstein rings or gravitational lensing.
From 1978 to 1996 the GBI was operated by the US Naval Observatory for its studies of Earth rotation (for accurate timekeeping) and monitoring of variable sources, such as pulsars. From 1996 until 2000 the GBI was in continuous use, funded partly by NASA, for studies of X-ray and Gamma-ray sources.
From 1995 until 2000, the GBI carried out a survey focused on the binary star systems Beta Persei and V711 Tauri — both are about 95 light-years from Earth. These stars orbit each other, but are pairs of different types of stars. Beta Persei is the prototype of the “Algol” class of interacting binary stars. An Algol system contains a hot, blue, main sequence star, along with a cool, orange/red star that is more active than our Sun. V711 Tauri is an “RS Canum Venaticorum” binary, which contains two cool stars that behave like our Sun. The continuous monitoring program, the longest ever completed, also demonstrated that Beta Persei and V711 Tauri have short- and long-term cycles, and active and inactive cycles. These data will help us to better understand our Sun’s activity.
The Green Bank Interferometer ceased operations on October 6, 2000, but the newer 85-foot telescopes had contract jobs for some years after, observing pulsars and other transient radio objects. They are still in working order and ready to take on new contract jobs.
- Reflector: 85-foot diameter paraboloid; Surface is 0.125 inch thick aluminum panels; Surface area is 5700 square feet with better than 0.125 inch RMS tolerance.
- Focus: 36 feet above reflector surface and 115 feet above ground; Carries 600 pounds of receiving equipment; position relative to paraboloid stable to 0.25 inch.
- Mount: Equatorial (polar and declination axis, mutually perpendicular)
- Declination Axis: Shaft is 40 feet long, 16 inches diameter; gear is 40 feet diameter; Travel is 132 degrees total, 48 degrees north of stow and 84 degrees south of stow.
- Polar Axis: Shaft is 23 feet long, 28 inches diameter; Gear is 48 feet diameter; Travel is about 90 degrees either way from stow.
- Drive Rates, Both axes: Slew is 20 degrees per minute; Scan is up to 4 degrees per minute.
- Material: Painted steel superstructure.
- Total Weight: 210 tons.
- Pointing Precision: About 30 arc seconds (about a quarter at 600 feet).
- Baseline: 2400 meters at an azimuth of 62 degrees (E of N).
- Bands: 8.3 GHz (X-band) and 2.25 GHz (S-band) with 35 MHz bandwidth.
- Receivers: Cryogenically cooled, dual frequency, dual polarization. Both X and S bands simultaneously observed in both right and left circular polarizations.
- System temperature: About 35 K in Sband and 45 K in Xband.
- Sensitivity: RMS noise in a 5-minute scan is about 6 mJy in S-band and 10 mJy in X-band for point sources.
- Minimum integration time: 30 seconds.
STEM research opportunities for students of most ages – from grade three to graduate school!
Some require your presence onsite, but we also have online opportunities.
Pocahontas County Science Fair
The Green Bank Science Center hosts the annual county-wide science fair for students in grade 3 and up. We’ll visit your school and help students design science and engineering experiments. On Fair Day, students spend the whole school day at the Observatory and participate in hands-on activities and demos, as well as having their projects judged of course! Watch this space for dates and more information.
What sets a scientist apart is that they tackle questions that don’t yet have answers. You can’t just “google it” when you are doing science. School groups and youth groups of all kinds and ages may visit the Observatory for an overnight stay or participate virtually! Conduct observations with a working radio telescope!
For in-person visits, we supplement the program with tours and hands-on activities as well. This program meets NGSS Nature of Science standards.
Program cost: Free!
Room & board: Costs vary, contact gro.y1708594937rotav1708594937resbo1708594937bg@sn1708594937oitav1708594937reser1708594937
For more information visit our field trips page.
Sharing the Universe with youth. That’s what Skynet Junior Scholars is all about. Youth Leaders and Educators sign up for Skynet Junior Scholars (SJS) and can then enroll students in an SJS Club. That’s when the fun begins!
Leaders and youth gain access to research grade telescopes around the world including a 20 Meter Radio Telescope here in Green Bank! Through a series of fun observational astronomy activities, you can take images and radio data, do experiments, earn online badges, and participate in research projects like tracking asteroids. Collaborate with others via our online forum and team projects. All the learning and observing is online, so what are you waiting for?
Visit the website to learn more. Skynet Junior Scholars is funded by the National Science Foundation.
The Pulsar Science Collaboratory (PSC) is a joint project between the Green Bank Observatory and West Virginia University (WVU), funded by the National Science Foundation (NSF). The goal of the PSC is to give high school students, and their teachers experience doing real research. With this experience they gain the confidence they need to succeed in STEM majors in college!
In 2007, the Green Bank Telescope was in need of repairs. Specifically, it needed a new track. While this track was being replaced, the telescope was unable to move and could only point at a fixed position in the sky. During this time, two astronomers from WVU, Dr. Maura McLaughlin and Dr. Duncan Lorimer used the Green Bank Telescope to observe the sky as it drifted overhead.
And as the sky drifted by, they took data. And more data. And more data! And they want to use this data to search for new pulsars. In 2008, we teamed up to form the PSC, and students have analyzed more than 2,500,000 pieces of data, and made some discoveries along the way!
In 2015, we expanded the program to include more than 10 colleges and universities around the country. Would you like to join the team? Twice each academic year we hold a six-week online course to prepare you to be diligent researchers. High school teachers and students can sign up. Once you pass muster you will be granted access to “raw” data, and the research begins. Active teachers and students may apply to summer camp and attend annual capstone events as well. We have a dedicated website for the project. Learn more and apply to become a PSC member!
We have held a summer student research program since the beginning of the Observatory in 1959! Undergraduate students spend 10-12 weeks on site participating in an astronomy, engineering or computer science research project. The project may involve any aspect of astronomy, including original research, instrumentation, telescope design, astronomical site evaluation or astronomical software development. The program runs from 10-12 weeks over the summer, from late May to mid-August. At the end of the summer, participants present their research results as a short talk and submit a written report. Often, these projects result in publications in scientific journals. Financial support is available for students to present their summer research at a meeting of the American Astronomical Society, generally at the winter meeting following their appointment.
This program is a collaboration between the National Society of Black Physicists (NSBP), the Green Bank Observatory (GBO) and Associated Universities, Inc. (AUI) to expose traditionally underrepresented minorities to science and engineering with a focus on physics and radio-astronomy. Launched in 2014, the the PING program focuses on multiple levels of the physics and astronomy pipeline, and includes a two-week summer camp that engages middle school students in physics and astronomy.
PING Summer Camp. Rising 9th-graders will attend camp for 12 days in 2024, and will be immersed in the research activities of Green Bank Observatory. Students will work in small teams supported by an undergraduate student mentor and a staff scientist (astronomer, physicist, engineer, etc.) to conduct research by observing the universe with a 40-foot diameter radio telescope. Supplemental educational activities, including bench experiences building electronic circuits, and coding activities complement the primary research theme and enhance our engaging atmosphere. In addition, fun group activities like star gazing, games, hiking, and talent-share sessions (where mentors teach campers anything from a new language to origami) will take place to promote community building and the overall camp experience. Applications are due May 27th, 2024. For more information, including application instructions, check out the website below!
The program targets specifically two White House initiatives, My Brother’s Keeper which is working to address the education needs of young men of color, and a second effort to promote interest in science among girls. However, all current 8th-graders (rising 9th-graders) are welcome to apply!
Questions about the PING program? Please contact ude.o1708594937arn@t1708594937niase1708594937ds1708594937
Join Green Bank Observatory to conduct research to help us characterize RFI for a new instrument being built for the GBT! Learn more and apply here.
Physics Inspiring the Next Generation: Exploring the Cosmos with Green Bank Observatory
The Physics Inspiring the Next Generation (PING): Investigating the Cosmos with Green Bank Observatory program is a collaboration between the National Society of Black Physicists (NSBP), the Green Bank Observatory (GBO) and Associated Universities, Inc. (AUI) to expose traditionally underrepresented minorities to science and engineering with a focus on physics and radio-astronomy. Launched in 2014, the the PING program focuses on multiple levels of the physics and astronomy pipeline, and includes an eight-ten week internship program designed to cultivate interest in physics and (radio) astronomy research in undergraduate students.
Undergraduate Internships provide stipends to undergraduate students for an 8-10 week experience at the Green Bank Observatory. Selected students will conduct research with a scientist/mentor, and will, in turn, participate in education and public outreach by serving as mentors for rising 9th-graders at the PING Summer Camp. PING internships are designed to broaden students’ skill sets, opening the doors for future employment and academic opportunities. Applications for PING internships are accepted through the NRAO Summer Student Program portal. Mentor applications for Summer 2023 are closed.
The program targets specifically two White House initiatives, My Brother’s Keeper which is working to address the education needs of young men of color, and a second effort to promote interest in science among girls. However, ALL current 8th-graders (rising 9th-graders) are welcome to apply!
Questions about the PING program? Please contact ude.o1708594937arn@r1708594937ehtae1708594937hs1708594937.
Besides their research, students take part in other activities, including a number of social events and excursions, as well as an extensive summer lecture series which covers aspects of radio astronomy and astronomical research. Students, may in their application materials also indicate a willingness to participate in PING, an opportunity to mentor rising ninth grade students who will be onsite for 2 weeks.
Applications for Summer 2023 are closed. We accept and review applications in conjunction with the NRAO summer student program. You can find more information about the GBO site’s program here, and see this website for information on the overall NRAO program!
Welcome Teachers and Youth Leaders. The Green Bank Observatory has some exciting opportunities that engage you and your students in STEM research.
Chautauqua Short Course
May 27 – 29, 2020 in Green Bank, WV
Chautauqua Short Courses are a 2.5 day program for college teachers, high school teachers, and amateur astronomers. At the Green Bank Observatory, we offer a course called Radio Astronomy Update.
Note: This course is sponsored by and offered at the Green Bank Observatory in Green Bank, West Virginia. Applications should be sent to the GBO Center. This course has course fee of $195 (in addition to the $100 application fee), which covers course-related expenses. Limited reduced rate on‑site lodging at about $35 per night will be available to early applicants.
This course is designed to celebrate more than 50 years of contributions to the forefront of astronomy by the telescopes of the National Radio Astronomy Observatory/Green Bank Observatory at Green Bank. During this time researchers using these telescopes have made major advances in our understanding of topics as diverse as chemical processes in interstellar space, the early phases of star formation, the assembly of galaxies and galaxy clusters at high redshift, the properties of black holes, and SETI.
The Pulsar Search Collaboratory (PSC) is an out-of this-world opportunity for formal and informal teachers and their students to join an international team of astronomers in searching for new pulsars! Your work actually helps to advance the field of pulsar science. All STEM teachers in grades 9-12, and their students, 13 and up, are encouraged to apply! The PSC is a national program, funded by the National Science Foundation. Teachers and students participate in a free online workshop to prepare you to analyze data. Once you have your astronomer’s credential, you can analyze brand new data taken by the Green Bank Telescope! For active PSC members, Capstone Events are held around the country AND a summer PSC Camp at the Observatory will hone your skills to the next level! Join us!
Research Experience for Teachers Dates TBD for 2020!
West Virginia University leads a collaboration with the Observatory to offer a six-week summer research program to 10 high school teachers each summer, called Digital Signal Processing in Radio Astronomy (DSPIRA). DSPIRA is funded through a grant from the Engineering Division of the National Science Foundation. Teachers will learn how to use a cheap, versatile and rapidly developing technology called software defined radio, which can be developed for astronomy applications as well as receiving signals from satellites like NOAA weather satellites! Successful applicants will spend 4 weeks working with WVU Engineers in Morgantown, and 2 weeks at the Green Bank Observatory, designing and testing software defined radio systems and piloting classroom activities with students. We are very interested in teachers who are interested in engaging their students in engineering activities. Applications are being accepted! Find out more at http://wvurail.org/dspira-2018/ Questions? Email Sue Ann Heatherly at sheather-at-nrao.edu.
The Education and Public Outreach Team leads a variety of outreach programs. When and where we can, we would love to participate in your STEM event whether in person or virtually. If you are a K-12 teacher in West Virginia, we encourage you to take advantage of our Science Public Outreach Team, a group of enthusiastic undergraduate students who deliver interactive presentations and hands-on activities about science happening in the mountain state. We partner with the West Virginia Alliance for STEM and the Arts on STEAM Trek, a virtual STEAM festival celebrating West Virginia STEM and the arts.
Bring Science and Engineering to Your School with WV SPOT!
The Green Bank Observatory partners with NASA and the West Virginia Space Grant Consortium to bring standards-based science presentations to your West Virginia classrooms! Trained college ambassadors visit K-12 classrooms with interactive presentations and hands-on activities through the West Virginia Science Public Outreach Team (WV SPOT).
WV SPOT increases K-12 student and teacher awareness of and interest in STEM research, programs, and careers in West Virginia, and students gain valuable exposure to college role models.
We train our college ambassadors at Green Bank Observatory in the immersive environment of the Quiet Zone. They learn in-depth science content knowledge, and they gain important “21st century skills,” such as science communication, public speaking, autonomy, and ability to adapt.
Visit the WV SPOT website to learn more! WV Educators – formal and informal – can submit a request for a WV SPOT Ambassador to visit their school or organization, and college students can sign up to become Ambassadors.
Not a WV resident and want to become involved? Read our publication about how to start SPOT in your own region!
We provide virtual field trips, and real-time demos using a robotic telescope to all educational organizations including classrooms , clubs and amateur astronomy groups. All educational activities are free.
If you have any questions not answered here or would like to request a virtual learning experience, contact our education team using the form at the bottom of this page. If you have any questions before requesting a visit, please contact us at gro.y1708594937rotav1708594937resbo1708594937bg@sn1708594937oitav1708594937reser1708594937.
General members of the public can sign up for virtual tours through the events calendar. Virtual visits are offered to educational groups of five or more participants only.