The Secret History of BU’s PRB Observatory and the Telescope It Was Built to House
The Secret History of BU’s PRB Observatory and the Telescope It Was Built to House
How a discovery at a Hawaii volcano sparked a project with a history unlike anything else on campus
Every day, hundreds of BU students walk down Cummington Mall, unaware that they are passing by a fascinating and unique campus relic, with a story full of drama, mystery, near-disaster, and earth-shattering scientific intrigue.
The unassuming observatory dome on the roof of the Physics and Biology Research Building (PRB) has a storied past: it was built to house a telescope that was eventually used at the South Pole.
The story of this observatory began in 1990 when astronomers at Mauna Kea, a mostly underwater volcano on the island of Hawaii, detected carbon in interstellar clouds that was 10 times brighter than anyone had expected. Interstellar clouds are accumulations of gas, dust, and plasma between star systems in a galaxy. Astronomers can determine the chemical compositions of these clouds by studying the radiation they emanate. The unexpected abundance of carbon detected on Mauna Kea was exciting—it could point to something new in the field of astronomy.
“The notion was that there may be a lot of atomic carbon that we’ve never properly mapped,” says Thomas Bania, a College of Arts & Sciences professor of astronomy. “Carbon is a very important atomic element, and if there’s a whole lot of carbon in atomic form that we don’t know about, it completely changes the way we study the chemistry of the interstellar medium and the chemistry of molecular clouds, things like that.” Detecting that much more carbon would radically change our understanding of the composition of significant portions of the Milky Way Galaxy, transforming our understanding of galactic evolution, the formation of stars and planets, and perhaps even the origin of life in the universe.
Eager to follow this lead, Anthony Stark, an astrophysicist at the Harvard Smithsonian Center for Astrophysics, teamed up with Bania and a team of astronomers from BU and Harvard to create the Antarctic Submillimeter Telescope and Remote Observatory (AST/RO) project. Their group included BU astronomy doctoral students Maohai Huang (GRS’00), Alberto Bolatto (GRS’01), James Ingalls (GRS’98), and undergraduate Edgar Castro (ENG’95). Together, they set out to design and build a telescope from scratch—one that they would eventually send all the way down to the South Pole for carbon observations.
Observational astronomers run into all sorts of issues when trying to operate a telescope in warmer environments: high wind speeds can shake the instruments, rapid temperature fluctuations cause metal and glass in the telescope to expand and contract, wet weather can damage the sensitive instrumentation, and nosy animals or errant birds can interfere with the telescope.
But these aren’t issues at the South Pole. It may not be a livable environment, but for over a century, astronomers have been conducting science in this inhospitable place, because with all the inconveniences of moderate climates, scientists have decided the benefits of what they might learn there make getting a bit cold worthwhile.
From 1990 to 1992, the AST/RO telescope was built from scratch at Bell Laboratories in New Jersey and BU’s Scientific Instrument Facility in the PRB basement. Its design is called offset Gregorian: once light enters the telescope, it bounces off four mirrors that direct it into a room below, called a Coudé room, where it is focused into an image.
As the telescope was being built, a team of BU Facilities Management & Planning workers constructed the test dome on the PRB roof. This was an ideal place to test the telescope since the rooftop had a clear view of the southern horizon (the Life Science & Engineering Building wasn’t there yet). One challenge, though, would be getting the telescope up there. The elevator goes only as high as the fifth floor—from there you have to climb another flight of stairs and then a ladder to get to the porthole that opens onto the roof. The AST/RO researchers made this climb every time they had to get to the observatory. That ladder is still the only way to get to the roof.
There was no way they could bring the telescope in pieces, one by one, up the ladder and through the two-foot-by-two-foot porthole. So the team installed a small crane inside the dome and used it to lift several of the telescope pieces from the fifth floor, through a series of hatchways—and through a biology lab—to the observatory. The biggest telescope pieces had to be hoisted onto the roof from a crane outside the building.
Once everything was assembled on the roof, the team spent 18 months testing the instrumentation. Huang remembers spending many long nights at the test site, even taking naps in the control room below the telescope. But every so often, he would wander up to the rooftop dome and enjoy a few quiet moments in the Boston morning. “There is nobody there, of course,” he says, as the sun is just beginning to crest over the city skyline in the east, “and you can see very far—you can see the Charles River, and everything.”
A long, dangerous journey, a telescope’s legacy
In 1995, the AST/RO telescope was finally ready for the South Pole. The team packed it up in a green-painted wooden crate (nicknamed the “Green Monster”). Its journey to the South Pole took three weeks and multiple modes of transportation: Boston to Los Angeles via truck, Los Angeles to McMurdo Station in Antarctica by ship, then McMurdo to the Amundsen-Scott South Pole Station aboard a C130 military plane.
But it did not go gentle: on the first leg of the trip, the truck carrying it crashed on a highway near Little Rock, Ark. Bania recalls going down to assess the damage with James Jackson, a CAS adjunct professor of astronomy. “We had the telescope, all of its computers, all of its electronics, all of the spares, all of the tools that it was going to take to put it back together, all of the documentation for an entire state-of-the-art high-frequency radio observatory in one truck,” says Bania. He and Jackson had to decide if it was worth the risk to send the telescope down to the South Pole, or if they should just bring it back to Boston and take stock of the damage there, losing a year in the process.
They decided to send it down to Antarctica. Fortunately, their gamble paid off—the telescope arrived in working condition.
The AST/RO telescope operated at the South Pole from 1995 to 2001. Bania and his students went down every year during the Antarctic summer (winter in the Northern Hemisphere) to perform maintenance and keep it operational.
In the end, though, the project was deemed a flop. “After 10 years of work, it turned out that, no, carbon was brighter for a different reason…and so there wasn’t this vast reservoir of atomic carbon,” Bania says. “And proving a negative never leads to a sexy press release.”
With that, AST/RO was unceremoniously boxed back up and left in a graveyard of other abandoned scientific instruments at the South Pole. It’s now probably buried under ice.
For those who spent hours, days, weeks, and years of their lives on the project, however, it was hardly a flop; all four BU grad students who worked on it got their doctorates and are still doing astronomy research. Huang, for example, is a research professor at the National Astronomical Observatory of China, where he works on the science operation and data processing system for astronomical systems, including the Herschel Space Observatory. “What I learned from AST/RO really directly goes into what I’m working on now,” Huang says. Controlling AST/RO was as difficult as controlling a telescope in space, he says: both are hard to access, so you’d better make sure things work the first time. If something breaks, it’s going to take a very long time to fix.
And, almost 30 years later, the AST/RO test dome remains atop the southwest corner of PRB, a monument to the team’s decade of work.
For those researchers like Bania, it stirs up mixed memories. “On bad days, I think I wasted 10 years of my life,” he says. “On good days, I think, well, you know, I had the opportunity to build an observatory from the ground up and operate it. Not many people can say that.”
AST/RO was sited at the geographic South Pole on the Antarctic Plateau. The Antarctic Plateau is the highest, driest desert on Earth. This makes the sky above almost as transparent as the vacuum of space. We needed this transparency in order to observe atomic carbon. For AST/RO to function in such a harsh environment it had to be designed and built as if it were a space mission, for 1/100 the cost of an actual space mission.