Dr. Paul Vanden Bout, the 58th Jansky Lectureship recipient, never planned to become an astronomer. He explained this in his lecture held at the Green Bank Observatory last Thursday.
Vanden Bout, of Charlottesville, Virginia, entered into astronomy after receiving a degree in physics. He was a postdoc at Columbia University where he studied x-ray astronomy. From there, he went on to University of Texas in Austin where he continued to learn about astronomy.
He soon became a pioneer in millimeter-wavelength astronomy at McDonald Observatory in Texas.
During this time, the National Radio Astronomy Observatory was proposing construction of an interferometer, which is an array of smaller telescopes, instead of building one large telescope. Vanden Bout explained that an array provides better angular resolution than you can get with a single dish.
“An angular resolution, by that we mean the finest detail you can see in a picture of the sky,” he said. “It depends on the wavelength that you use to make the observation, divided by the diameter of the telescope. For an interferometer, it’s the wavelength divided by the largest separation of antennas.”
At the same time of that proposal, there was another proposal in 1982 for a national millimeter array. the proposal didn’t get much traction at first, but 38 years later, that proposed array was dedicated – the ALMA –Atacama Large Millimeter Array, in northern Chile.
“So what took so long?” Vanden Bout said. “Indeed we were asked this question more than once by our colleagues. Well, there were big distractions. There was the Very Long Baseline Array. Then there was the Green Bank Telescope, and we all wanted to expand the VLA [Very Large Array], it needed upgraded. It was falling apart. All of these things took a great deal of time.”
In 1985, Vanden Bout became director of the NRAO, which at the time included the Green Bank facility.
One of the big distractions he mentioned – the Green Bank Telescope – came to fruition due to the loss of the 300-foot telescope which collapsed November 16, 1988.
“We come to the 300-foot telescope, which had a long, glorious history, but did not do well in a review that NSF [National Science Foundation] commissioned of all its radio facilities,” Vanden Bout said. “It got a pretty low mark. In a sort of fit of embarrassment, it collapsed.
“Later on, we discovered that it was really metal fatigue,” he continued. “There were incipient cracks in some of the supporting plates that Jim Condon drove to completion by exercising the antenna in an all sky survey.”
On the night the telescope collapsed, Vanden Bout was confronted with thoughts of an unknown future.
“George Seislstad called me up at eleven o’clock at night and said guess what?” he recalled. “And I didn’t believe it at first. It was amazing. I saw it the next day. You kind of got over the initial shock. There was an investigation and so forth. And then, I started thinking about it. I thought this could be the end of Green Bank.
“I mean, the telescope’s gone,” he continued. “The 140-foot didn’t have a lot of demand at that point. In fact, it was closed a few years later, and I thought it doesn’t look good for Green Bank at all.”
George Seielstad had the same feelings and reached out to a member of Senator Robert C. Byrd’s staff and set up a meeting with Byrd and Senator Jay Rockefeller.
“So we found ourselves, very quickly, in Senator Byrd’s office,” Vanden Bout said. “He was majority leader in the senate with Jay Rockefeller. So there’s me and George and Eric Block from NSF, and Bob Hughes from AUI [Associated Universities, Inc.]. Jay Rockefeller’s on the other side of the table, he did all the talking.
“He stood up and he sort of loomed over Block and he said, ‘we want to help you.’”
Vanden Bout said Block told Rockefeller that NSF didn’t know what its plans for Green Bank were at this time and they needed to set priorities and so forth.
“Rockefeller interrupted him and he said, ‘leader here’ – referring to Byrd – ‘is going to be chairman of appropriations next year and he will have his thumb on every dime in the federal budget,’” Vanden Bout said. “He said, ‘now do you understand what I mean when I say we want to help?’ That was pretty clear that we were going to get a telescope – whether we wanted one or not – we were going to get a telescope.”
Work went into designing the Green Bank Telescope, which was also named for Byrd. The telescope looked like no other at Green Bank and was taller than the Statue of Liberty. It also was more versatile than any telescope that came before it.
“It had to be very versatile,” Vanden Bout said. “It had to go to higher frequencies, so the surface of this thing, all these panels were supported by motorized actuators that would correct the surface as you tipped it up and down. We said, with luck, it’s going to work at millimeter wavelengths – which was taken with some skepticism – I think, by the community.
“But, in fact, the thing does work at millimeter wavelengths,” he continued. “It’s unbelievable.”
Getting the world’s largest fully steerable telescope built wasn’t as smooth sailing as they had hoped, however. The contractor, Radia- tion Systems, was contracted to build the telescope for $55 million. They spent $120 million in the end.
“By our interpretation of the specs, the mechanical parts were to be guaranteed for twenty years,” Vanden Bout explained. “By that they meant the motors and we meant the whole thing. And insisted on that which meant they had to beef up the structure and it weighed more, and it cost more to produce because it weighed more and needed more members and everything else.”
The contractor filed claims against NRAO and asked for $30 million from the observatory. Vanden Bout counteroffered with $4 million which they rejected with outrage.
The matter was taken to court and the judge decided the NRAO owed Radiation Systems $7 million and Radiation Systems owed the NRAO $3 million.
“The difference being exactly what they were offered before we hired lawyers,” Vanden Bout said.
The other distractions from ALMA were the Very Long Baseline Array – VLBA in Socorro, New Mexico and repairs to the VLA, also in New Mexico.
The VLBA began construction in February 1986 and was completed in May 1993. The repairs to the VLA went on to be upgraded and renamed to the Karl G. Jansky Very Large Array in 2011-2012.
Finally, focus went back to the ALMA and it was dedicated in 2013.
“It cost over a billion dollars and was it worth it?” Vanden Bout said of ALMA. “Well, here’s HL Tauri, a young star and it has a protostellar disk. People looked at it with infrared telescopes and had infrared access. There’s some heated dust around it.”
After showing that image, Vanden Bout showed another image of the same star that was taken with ALMA.
“It’s much bigger,” he said. “In fact, there is a heated disk around it, but when you look with ALMA, this is what you get. You resolve the disk and all these rings. It’s fantastic. You see the heated dust, but you see these dark lanes in between where the dust is agglomerated.
“You’re looking at a solar system in formation here,” he continued. “When people saw this image, they were just blown away. They thought it was fantastic. It was worth it.”
The HL Tauri is just one of dozens of stars being mapped by ALMA. Many of those stars have solar systems.
“Hundreds have been imaged,” Vanden Bout said. “They’re not all that far away in the galaxy. When you think about how many there must be in the galaxy and how many galaxies there are, what are the odds we’re alone?”
During his tenure with NRAO, Vanden Bout experienced a multitude of new projects and discoveries with the new machinery, including the GBT.
“What I want to say is that NRAO is the premier radio observatory on the planet,” he said. “The reason the facilities are so great has everything to do with the people that make up the staff and, for me, it was a pleasure and an honor and a real privilege to be part of that team.”