Massive Science: The Green Bank Telescope

Deep in the National Radio Quiet Zone, a behemoth of steel and aluminum quietly peers out into our Universe, looking for radio and microwaves coming from the farthest and faintest objects. The Robert C. Byrd Green Bank Telescope (GBT) is the largest, fully steerable radio telescope in the world. The ACEAP team had the opportunity to visit the Green Bank campus last week, and even to climb up on the GBT!

The Green Bank Telescope, about 2 miles off. Apologies for the fuzzy zoom. Image: Renae Kerrigan

Because the GBT is a very sensitive radio telescope, the radio waves that abound in modern daily life would create a huge amount of interference for its observations. As my friend and fellow ACEAP member Brian Koberlein explains very well here, many items we use every day produce radio waves. Your cell phone, bluetooth, digital camera, and even car engine (unless you drive a vehicle that uses diesel fuel) create radio waves that are very bright compared to the faint signals coming from distant objects in the Universe. Because of this, the National Radio Astronomy Observatory (NRAO) campus in West Virginia is protected by the National Radio Quiet Zone. There is no cell coverage and no wifi in the 13,000 square miles surrounding the NRAO campus. Life goes on - most people have cable or satellite television, and wired internet. The only difference was having periods of time (when we were away from our desk area) that we weren't connected to the wider world. I was not able to tweet while on the telescope, or update the Dome Facebook page on my phone. It was nice to get away from instant communication for a few days. 
 

Two workers walk across the 2.3 acre mirror of the GBT.

Because digital cameras are not allowed near the GBT, I brought my grandfather's old film camera. I also brought the film that was in the bag - not knowing much about film photography, I didn't realize that using film that was at least 10 years old is a really bad idea. My pictures didn't turn out well, but they are better than nothing at all. 

We were given a tour by Bob Anderson, who has worked at the GBT for 13 years. He is the Head of Operations, and so was great at answering all our questions. Mike Holstine is the Business Manager at Green Bank, and was touring a BBC film crew when we were there. These men, plus many other workers, keep the telescope working - not an easy task. They are very efficient with their maintenance. The GBT observes approximately 6,500 hours of the 8,760 hours in a year. They usually devote about 2 days (or in most cases, parts of days) per week to maintenance, and they try to arrange it at the least optimal time for observing. We got to go up on the scope because it was in the upright maintenance position. Workers were replacing a light bulb on the edge (see above photo) and greasing one of the wheels that allows the GBT to rotate.
 

Bob Anderson and Mike Holstine with the dish of the GBT in the background.

The computers that are on the GBT are shielded with copper to trap the radio waves inside. It has diesel generators as backups to the main power supply, shown below. 

 We used elevators to climb up the main shaft of the telescope, all the way up to the platform just below the secondary mirror! We were 120 stories up (485 feet) - higher than the Statue of Liberty. 

The secondary mirror of the GBT.

The secondary mirror of the GBT is 8 meters in diameter. That is the same size as the primary mirror of another telescope the ACEAP team visited, Gemini South! 

The ACEAP team at Gemini South - the main mirror of Gemini South is the same size as the secondary mirror at the GBT!

We were very high up. It was very windy, and beautiful.

At the top of the GBT. The 43 meter (140 foot) telescope is the large dish in the background.

We went to the top first because Bob was worried the rain threatening would force us off. On the way down we stopped at the platform parallel with the main dish. It was so huge I couldn't get the whole thing in my camera frame. It was hard to absorb how big it was just looking at it! 

The main dish of the GBT is 100 meters, or 328 feet, in diameter. You could sit the entire International Space Station on the dish. This enormous size, and the fact that it is an active surface (the shape of the dish can be changed to better observe in different conditions), allow astronomers to make very sensitive measurements using the GBT. The GBT is fully steerable - also enhancing it's versatility. It rests on wheels to allow it to turn 360 degrees. No easy feat since it weighs 16,720,000 pounds! 

This photographer did a better job capturing the size of the GBT mirror than I did. Image Credit: NRAO

 

The platform we were standing on it just below the secondary mirror, tilted over when the telescope is in use.

Besides getting a tour of the telescope, we were given training on radio astronomy, and even had our own research projects to carry out. My team was measuring the hydrogen in the Milky Way. We made two measurements, one at 7 PM, and the next at 4 AM - we had to wait for the Earth to rotate into the proper position, since the 40 foot telescope we were using was not fully steerable. 

Peter and I analyzing our data. Photo by Jim O' Leary.

Astronomy and wine, a delightful combination. Photo by Jim O'Leary

The lounge that we spent much of our evening time in is the room that Frank Drake announced his equation - the likelihood of finding other intelligent life in the Universe. Photo by Jim O'Leary

It was a real treat to spend time on the Green Bank campus. I love being in an environment of science. We had fascinating conversations with astronomers and astronomy educators. The sky was very clear the first night we were there, and we saw a Taurid fireball - it lit up the sky! 

Hmmm, there must be geeks here....

Besides being in a stimulating mental environment, it was just plain beautiful there. 

You can visit Green Bank too! They don't usually let visitors up on the scope, but they have daily public tours, and a very nice science center. If you are in West Virginia, it is definitely worth your time to visit.

In case you missed my post about it earlier, Peter and I did a little astrophotograpy at Green Bank. Peter helped me process a bunch of images taken over a two hour period into this startrail picture:

Image by Peter Detterline and Renae Kerrigan

I am grateful to have had this time of professional development and fun at Green Bank! You can read more about my astronomy explorations with the ACEAP program here. And don't forget, you can always learn about space and science at the Dome Planetarium!