Cooled by a gentle breeze and shaded by the native algorrobo trees overhanging the terrace of the La Casona restaurant in San Pedro de Atacama, Chile, scientists from around the world listened, rapt, to presentations on the construction challenges, technical details and promise of scientific discovery of the innovative Fred Young Submillimeter Telescope (FYST). Many of them had been working on the telescope for more than a decade and the information shared at this workshop mattered: tomorrow they would visit the assembled telescope at its mountain top home for the first time, as part of FYST’s formal inauguration April 9.
“This is the end of the beginning and the beginning of the time that we're going to utilize it, so it's kind of an intersection in life. It's a marvelous time,” said Fred Young ’64, M.Eng ’66, MBA ’66, after whom the telescope is named.
Workshop speakers emphasized the collaborative nature of the project along with FYST’s technical innovations and breakthrough science. FYST is a project of the CCAT Observatory partnership, led by Cornell University and including Germany’s University of Cologne, University of Bonn, Max Planck Institute for Astrophysics, a Canadian consortium of universities led by the University of Waterloo, and Duke University, in conjunction with Chilean astronomers through the University of Chile.
“Astronomy is one of the truly international and global fields of scientific endeavor. I don't know that there's another field that crosses so many borders and so many boundaries intellectually and politically,” said Peter Loewen, the Harold Tanner Dean of Arts and Sciences, during a break in the inauguration events. “The important thing about FYST is that it takes a broader view, a bigger picture view of the universe in the relatively unexplored submillimeter window. And that's only possible because Fred Young shares this big vision and I'm just deeply, deeply grateful and inspired.”
FYST surveys promise a leap forward in our understanding of galaxy, star and planetary formation processes, said workshop presenters. Such processes take place in environments heavy with interstellar dust, which absorbs visible light and re-emits it in the infrared and submillimeter wavelengths, as explained by Frank Bertoldi of the University of Bonn.
But Earth’s atmosphere obscures the submillimeter signal because water vapor both absorbs cosmic radiation and emits its own. Thus, FYST’s extreme elevation – at 18,400 feet, it’s “the highest site you can drive a truck to,” the late Cornell professor Riccardo Giovanelli, who originally conceived of the telescope project and pushed for its development for 20 years, used to say – matters, because water vapor is generally confined to the lower levels of the atmosphere. And the Atacama Desert, one of the driest places on Earth, is “Mother Earth’s gift to astronomers,” said Martha Haynes, Distinguished Professor of Arts and Sciences in Astronomy emerita in the College of Arts and Sciences and CCAT board chair.
FYST scientists have taken full advantage of this ideal location, as they explained during the presentations.
Michael Niemack, professor of physics and astronomy (A&S) presented on Prime-Cam, the massive FYST instrument whose design he led. “I believe it to be the largest submillimeter instrument that’s ever been built, both in physical size and most importantly in the number of detectors,” he said, thousands of which can fit on a single silicon wafer. Prime-Cam’s tens of thousands of detectors will be increased over the next couple of years “by roughly an order of magnitude, a factor of ten, compared to previous instruments. That allows us to map and measure the submillimeter sky ten times faster than anyone has been able to in the past. There’s a whole wide range of astrophysical and cosmological questions we can pursue with that advanced capability,” Niemack said.
The Prime-Cam receiver is designed to hold seven instrument modules with three detector arrays per module.
Dominik Riechers of the University of Cologne explained in his presentation on the CCAT Heterodyne Array Instrument (CHAI) that the high-resolution spectrometer will be able to scan wide areas of the sky, targeting especially the key spectral lines of carbon and carbon monoxide, looking at when and how the process of star formation begins. Amelia Stutz of the University of Concepción explained how CHAI will also allow scientists to better understand the total amount of molecular gas, and thus to estimate the amount of gas available for new star formation in different environments within the Milky Way and Magellanic Clouds.
Eve Vavagiakis ’14, Ph.D. ’21, who leads an instrument team at Duke University, presented a broad overview of how FYST will contribute to important new studies of the Cosmic Microwave Background (CMB), the oldest light in the universe, emitted only 400,000 years after the Big Bang. Offering entirely new capability to map the CMB at submillimeter wavelengths, FYST will allow astronomers to dissect the CMB in new ways and to remove contamination of the CMB light by dust in the Milky Way. As the CMB travels through space, it interacts with matter. FYST will be able to perceive some of those interactions, giving insight to what happened even before galaxies formed, including the long-hypothesized epoch of inflation.
“It may even see signals of CMB scattering that have been theorized but never before measured,” said Vavagiakis.
During the lunch break, as waiters delivered plates laden with local cuisine, CCAT Project Director Gordon Stacey, M.S. ’82, Ph.D. ’85, chatted about one way Prime-Cam will be used to study the CMB by examining how the CMB photons are deflected as they pass through the hot gas that fills galaxy clusters – the most massive, gravitationally bound entities in the universe. While the thermal effects of those interactions, which indicate the amount of matter in the cluster, have been studied extensively, “the kinetic effect hasn't been well explored because it's very challenging,” said Stacey, the David C. Duncan Professor in the Physical Sciences (A&S). “That's one of the things I think FYST's really going to hammer. We’ll learn about the underlying structure of the universe, how the biggest things in the universe formed, really cool information about fundamental physics.”
A novel technique called line intensity mapping that will be used by FYST also has scientists excited. It’s used to map ionized carbon and other elements caught in the “cosmic web” at different cosmic epochs. FYST’s wide angle capability enables scientists to make line intensity measurements much more quickly than previously.
Stacey leads the development of a module for PrimeCam dubbed EOR-Spec (Epoch-of-Reionization Spectrometer) that will attempt to measure emission from the first galaxies at “Cosmic Dawn.” “It will map out a history of galaxy formation over cosmic time, and the growth of structure over cosmic time in a region that's very important because it’s where this dark energy weird stuff starts to happen,” said Stacey.
“We haven’t been able to use line intensity maps in this way previously because it is far too challenging to use observations of galaxies one at a time,” explained Nicholas Battaglia, project scientist and associate professor of astronomy (A&S). The FYST line intensity mapping survey will focus on detecting emissions from aggregates of galaxies (groups and clusters) over bigger volumes so that the weak signals from the individual galaxies are added together.
One of the most pressing questions of contemporary cosmology, said speaker Renée Hložek from the University of Toronto, is understanding the epoch of reionization, when neutral hydrogen was heated by the first stars, ionizing it (removing electrons from an atom turns it into an ion, a charged particle). By tracing how the filamentary distribution of galaxies and galaxy clusters develops over cosmic time through line intensity mapping, astronomers will be able to measure the expansion history and the growth of structure across vast cosmic volumes, thereby revealing how much dark matter there is in the universe.
Additionally, FYST’s observations will help define whether dark energy varies with time or is some kind of cosmological constant, said Norman Murray, CCAT board member and professor at the University of Toronto, during a break. “That's one of the really exciting things that I think will come out of the CCAT Observatory.”
Speakers encouraged the audience to go outside and look up at the Atacama Desert’s night sky to know why astronomers have come to this remote spot. Here, the disk of the Milky Way, impossible to miss, stretches as a band across the darkness. The brightest spot marks the heart of the Milky Way and its supermassive black hole, itself obscured to our eyes by the very dust that FYST will study.
“The sky overhead here in the southern hemisphere is glorious,” said Haynes. “We see our nearest neighbor galaxies, the Large and Small Magellanic Clouds, and we see millions of points of light. The culture of this area, which has been inhabited for 5,000 years, has always revered the skies and you can understand why.”
The Chilean government created the Parque Astronómico Atacama (Atacama Astronomical Park) to protect the Atacama Large Millimeter/submillimeter Array’s plateau and the mountains around it, said Leonardo Bronfman, of the University of Chile and CCAT Board member, in his talk on the history of astronomy in Chile. In return for the welcome Chile has extended to the international telescope projects, Chilean astronomers participate in the FYST survey teams. For example, Manuel Aravena of the University Diego Portales leads the key project to trace the star formation history of dusty galaxies from early times through “Cosmic Noon,” the era when the Sun was formed about five billion years ago, as he explained in his talk.
One of the important benefits of FYST, said workshop speakers, is that, because the telescope is readily accessible, scientists can upgrade the instrumentation as new technologies are developed, a flexibility that suborbital or space instruments don’t allow.
It’s clear that there’s much we don’t understand about early galaxy evolution, Niemack said; “There's tremendous potential to make great progress in identifying some of the youngest galaxies with initial Prime-Cam measurements. And then in the future, with new technologies that we're pursuing now, we’ll be able to potentially expand our sample by another order of magnitude within the completed instrument.”
Abigail Crites, assistant professor of astronomy and physics and Fred Young Faculty Fellow (A&S), is hard at work on one such instrument, a next generation spectrometer to go on Prime-Cam. It will focus on measuring frequencies that are complementary to Stacey’s EOR spectrometer, with the goal of increased sensitivity in detecting carbon monoxide and carbon during the epoch of reionization, providing critical information about the early structure of the universe and the way it evolved.
“To me, building a telescope and observing the early universe is the same as making art, or writing a book; it's creating something, and it's also discovering some new depth to our world,” said Crites.
Studying cosmic dawn – watching the star-forming galaxies light up the universe – “excites me tremendously,” said Haynes during a break. “We're going to contribute to the time frame of cosmic dawn in a completely unique way – something that, until this telescope, we could only dream of doing. It's exciting to know that something people have been talking about for decades will now actually be done.”
A new focus for researchers called time domain astronomy – how things vary in time and how they evolve – will be one of FYST’s great strengths. As Doug Johnstone, of Canada’s NRC Herzberg Astronomy and Astrophysics Research Centre outlined in his talk, FYST will provide relatively long-term monitoring, from days to years, of dust production in supernovae; matter shooting out of black holes; how comets change; and the variability of protostars. FYST’s unique design makes this unprecedented monitoring possible; it has access to a large fraction of the sky at any given time and its large dynamic range allows it to precisely monitor both bright and faint sources.
For example, FYST will enable study of protostars, the birth places of stars and planetary systems. These can only be monitored in the submillimeter and infrared wavelengths, and infrared requires space and expensive telescopes that don't last very long, said Johnstone. Protostars must be observed for five to ten years to determine how they’re building up their mass, something possible with FYST, he said.
The telescope’s agility – including fast triggering and its ability to turn quickly to focus on targets, as well as its timing accuracy and fast time-sampling – will enable it to provide monitoring over seconds to days, Johnstone said. FYST will be able to look for submillimeter counterparts to compact or explosive sources observed at other wavelengths, electromagnetic radiation associated with gravitational waves, and flaring from stars, he said. The combination of clues provided by observations with different telescopes at different wavelengths will allow astronomers to develop a complete history of such explosive events.
Stephen Parshley ’98, M.Eng. ’09, the project engineer, gave a wide-ranging presentation that traced the evolution of the telescope from its first conception to its final stage. He emphasized the telescope’s “next-generation science” capabilities in scale, speed, sensitivity and capacity. As one of the largest submillimeter survey telescopes ever built, it maps “orders of magnitude faster” than its predecessors, he said, and carries a “generous” payload for current and future instrumentation, with Prime-Cam’s ability to hold up to seven different instruments at once giving it a unique versatility.
Unlike many other telescopes, FYST can observe “past zenith” and can stow itself “below the horizon” for weather protection, because of the novel design of its mounting structure. The rigid main structure, combined with powerful motors and advanced control system enable FYST to go from full speed in one direction, stop and turn in the other direction in a mere 2.5 seconds, an engineering feat for a 230 ton telescope.
The most critical part of the telescope, the mirrors, features an innovative Crossed-Dragone design first proposed by Niemack. It has as a two-part system: as it arrives from the sky, light bypasses the secondary mirror which is set off-center and hits the primary mirror, which reflects it up to the secondary mirror, which then directs it into the detecting instrument.
Because the path of the light is off-center, the mirror doesn’t block the incoming signal, reducing distortions in the image. The design allows for the wide field of view essential to FYST’s science goals, allowing it to see a very large area of the sky at once. It also retains the polarization – the angle that light waves oscillate – critical for studying the first inflationary moments after the Big Bang.
Aligning the “crossed” part of the design for the 146 separate sections of the mirrors with their 438 locators and 730 microadjustors, though, could have derailed the project, if not for the late University of Cambridge mathematician and physicist Richard Hills. He became intrigued by the mathematical challenges that the multiple angles presented and took it on as a side project, gratis. As leader of the team, he worked out the math that made the mirrors possible – and, said Haynes, he did all his math by hand.
The mirrors are mounted on a carbon fiber reinforced plastic subframe of a special material “made in only one factory on the planet Earth and that factory had a fire. It put us two years behind very early because we couldn't get the carbon fiber threads that we need,” said Peter Fasel, managing director of CPI Vertex, the company that constructed FYST. But that special carbon was essential because of its excellent stiffness-to-weight ratio, a necessity for mirror assemblies that would each weigh about two tons when completed.
As audience member Achim Tieftrunk of the DFG (German Research Foundation) said later, “if it was fast, predictable and risk-free it wouldn’t be frontier science.”
The Atacama Desert sits in a subduction zone, where the South American Plate converges with the Nazca Plate, creating the more than 2,000 volcanoes in Chile, including the lava dome that is Cerro Chajnantor, on whose summit FYST rests. Earthquakes in such zones are common, and FYST was built with this in mind, said Parshley, with the telescope easily able to withstand the magnitudes typically recorded in the region.
Wind, too, poses a threat to structures at FYST’s elevation, with multiple wind events recorded at the CCAT summit exceeding 110 miles per hour. The telescope can observe in winds up to 34 mph; higher than that and it goes into protective mode, turning upside down and sliding on special protective shutters to guard the instruments.
Thanks to the Invar used in the structure, a nickel-iron alloy which minimizes sensitivity to temperature changes, FYST can operate in sub-zero temperatures as well, down to -6 Fahrenheit, and does just fine waiting out cold down to -22 Fahrenheit.
The instruments themselves, though, need to be kept “colder than outer space” to operate, according to project manager Jim Blair. Cooling the instruments down to 4 degrees Kelvin and colder can take up to two weeks. The cryogenic system that does this draws the biggest power of any part of the telescope, and since keeping the instruments cold is crucial to observing, CCAT installed an 80,000-liter (21,000 gallon) fuel tank in the power plant at the base of the mountain. This way, said Blair, it can be reached easily even during winter storms when the road to the summit is impassable; it can take three weeks to dig out the road to the summit when it snows hard. The final ascent to the FYST site climbs steeply, zigzagging amidst giant boulder-filled slopes and scree, switchback turns and heart-stopping close edges, though berms have been raised for greater safety.
Most of the roads in the Atacama Desert remain unpaved – they’re just packed, rutted dirt with the odd rocks scattered across. The hour-long journey from San Pedro de Atacama, the nearest town, to Cerro Chajnantor moves through a landscape eerily reminiscent of Mars. The rough rocks and mineral-rich surface, formed by volcanic action, has proved invaluable to NASA for testing Mars rovers and instruments.
In this dry desert, even the sun proved a hurdle for the FYST project team, its ultraviolet light at 18,400 feet almost double the “extreme” rating at lower levels. The high, thin clouds prevalent in the Atacama Desert can magnify the UV rays as well, quickly degrading exposed plastic at the summit. Plastic-coated wires for FYST therefore had to be buried, and a special paint was used on the telescope to protect it from the UV rays.
By the time Dr. Thomas Küpper from the University Hospital RWTH Aachen, Germany, stepped onto the stage for the final workshop presentation, the audience could be forgiven if their attention had strayed occasionally to their virgin pisco sours (no alcohol before going to extreme altitude to visit FYST) and mint-ginger lemonade. But Küpper’s first words caught their attention with a laser focus.
Küpper had advised the CCAT team on safety measures for extreme altitude, and his depiction of what happens to the body at that altitude was sobering. He explained that while oxygen at the summit is in the same concentration as at lower elevations, the atmospheric pressure is lower, so less oxygen reaches the cells. In addition, the pulse rate increases 20-50% at altitude, while you lose 10-15% of exercise capacity for every 1,000 meters of altitude. Balance and coordination are reduced; he advised FYST visitors to pay careful attention to where they stepped.
As the ancient Incas knew, he said, permanent acclimation is only possible up to 5,300 meters (17,338 feet). Even the FYST construction workers require continuous oxygen and had to be rotated out on a seven days on, seven days off schedule to protect their health.
The next day, when nearly 100 people visited the telescope, a safety crew following Küpper’s guidelines moved among the visitors throughout the afternoon, checking their pulse oxygen and ensuring that the heavy oxygen tanks each person carried were still comfortably full – and to remind people to breathe deeply and move slowly, as even the slightest exertion could set hearts racing.
That first sight of the telescope set hearts racing as well.
"As I caught a first glimpse of the telescope from the beginning of the access road, still far away high up on the mountaintop, I thought: it looks so white, and we really can drive a truck there!” Haynes said later. “After so many years of dreaming, planning, writing proposals, seeking more funding, drafting agreements, evaluating options, justifying choices, monitoring progress, finding work-arounds, reacting to setbacks, and just plain a lot of hard work, I could hardly believe my eyes.
“But there FYST was, the mirrors reflecting light from the sky, just about ready to begin to scan the cosmos from this truly remarkable place. It seems that this dream has come true. We’ve done it."
Thankfully all the visits to the summit went smoothly, and no one had to miss the final event of the inauguration, a celebratory dinner April 9 at the Puribeter Elemental Reserve. The dinner began with a traditional blessing ceremony led by an Indigenous Lickanantay woman that included scattering popcorn on the tables to represent abundance and pouring a drop of wine onto the earth as an expression of thanksgiving.
At the end of the dinner, Blair officially turned over the reins of management to Parshley, to mark the transition from a construction project to an operating observatory. “Steve Parshley is the right leader for the next phase,” Blair said in a tongue-in-cheek presentation that included a white horse, a Napoleon hat, and multiple packages of red pens for editing proposals. “He knows the science and knows what the instruments need.”
After tributes to Hill and Giovanelli and thanks to Young for his support and Haynes for her leadership, the official inauguration of FYST formally concluded, with participants already focused on the next phase of the FYST journey: installing the instruments, Prime-Cam and CHAI, and anticipating First Light later in the year.
