In four years, an extraordinary new telescope on a mountaintop in Chile will begin the most powerful sky survey ever undertaken. When it does, it will depend on highly sophisticated optical assemblies designed at Lawrence Livermore National Laboratory.
The telescope — Large Synoptic Survey Telescope, or LSST — will include three lenses, one of them thought to be the largest high-performance optical lens ever fabricated, at 5.1 feet (1.57 meters) in diameter.
That lens, and its smaller companion at more than 3.9 feet (1.2 meters), are part of an assembly built during the past five years by Boulder, Colorado-based Ball Aerospace and its Tucson-based subcontractor Arizona Optical Systems.
Mounted together in a carbon fiber structure, the two lenses were shipped from Tucson. They arrived after a 17-hour truck journey intact at the SLAC National Accelerator Laboratory in Menlo Park.
SLAC is managing the overall design and fabrication, as well as the sub-component integration and final assembly of the $168 million, 3,200-megapixel digital camera. It’s now more than 90 percent complete and due to be finished by early 2021.
In addition to SLAC and LLNL, the team building the camera involves an international collaboration of universities and labs, including the Paris-based Centre National de la Recherche Scientifique and Brookhaven National Laboratory.
“The success of the fabrication of this unique optical assembly is a testament to LLNL’s world-leading expertise in large optics, built on decades of experience in the construction of the world’s largest and most powerful laser systems,” said physicist Scot Olivier, who helped manage Livermore’s involvement in the project for more than a decade.
He said without the dedicated and exceptional work of LLNL optical scientists Lynn Seppala and Brian Bauman, and engineers Vincent Riot, Scott Winters and Justin Wolfe, spanning nearly two decades, the LSST camera optics, including the world’s largest precision lens, would not be the reality they are today.
“Riot’s contributions to LSST also go far beyond the camera optics. As the current project manager for the LSST camera, Riot is a principal figure in the successful development of this major scientific instrument that is poised to revolutionize the field of astronomy,” Olivier said.
LSST Director Steven Kahn, a physicist at Stanford University and SLAC, said Livermore has played a significant technical role in the camera and a historically important role in the telescope design.
Livermore’s researchers made essential contributions not only to the optical design of LSST’s lenses and mirrors, but also to the way it will survey the sky and how it will compensate for atmospheric turbulence and gravity.
LLNL personnel led the procurement and delivery of the camera’s optical assemblies, which include the two big, completed lenses and a third still to be completed. That lens, at 2.3 feet (72 centimeters) in diameter, is expected to be delivered to SLAC within a month.
The assembly also includes a set of filters to cover six wavelength-bands, all in their final mechanical mount.
Livermore focused on the design, then delegated fabrication to industry vendors, although the filters will be placed into the interface mounts at the lab before being shipped to SLAC for final integration into the camera.
The 8.4-meter LSST is expected to make digital images of the entire visible southern sky every few nights, revealing unprecedented details of the universe and helping unravel some of its greatest mysteries.
During a decade, LSST will be able to detect about 20 billion galaxies — the first time a telescope will observe more galaxies than there are people on Earth. It will create a time-lapse “movie” of the sky.
Its data will be sent out to astronomers around the world in such an intense stream that new methods are being developed to manage the flow.
The information will help researchers study the formation of galaxies, track potentially hazardous asteroids, observe exploding stars, and better understand the elusive dark matter and dark energy that together make up 95 percent of the universe.
The telescope’s camera is the size of a small car and weighs more than three tons. It will capture full-sky images at such high resolution that it would take 1,500 high-definition television screens to display just one picture.
Research scientists aren’t the only ones who will have access to the LSST data. Anyone with a computer will be able to simulate flying through the universe, past objects 100 million times fainter than can be observed with the unaided eye. The project will provide a platform so students and the public can participate in scientific discovery.
Riot, who started on the LSST project in 2008, initially managed the camera optics fabrication planning. In 2013, he became the LSST deputy camera manager and was promoted to full camera project manager three years ago. Since 2017, he’s worked at LLNL and at SLAC on special assignment.
“There are important challenges getting everything together for the LSST camera,” Riot said. “We’re receiving all of these expensive parts that people have been working on for years and they all have to fit together.”
He and Wolfe, an LLNL optical engineer and the LSST camera optics subsystems manager, are pleased that the world’s largest optical lens has overcome hurdles.
“Any time you undertake an activity for the first time, there are bound to be challenges,” Wolfe said. “Every stage was crucial and carried great risk. You are working with a piece of glass more than five feet in diameter and only four inches thick. Any mishandling, shock or accident can result in damage to the lens. The lens is a work of craftsmanship and we are all rightly proud of it.”
“When I joined LLNL, I had no idea that it would lead to the opportunity to deliver first-of-a-kind optics to a first-of-a-kind telescope,” he added. “From production of the largest precision lens known, to coating of the largest precision bandpass filters, the LSST optics have set a new standard.”
Livermore’s involvement in LSST started around 2001. It was spurred by the scientific interest of LLNL astrophysicist Kem Cook, a member of the Lab team that previously led the search for galactic dark matter in the form of Massive Compact Halo Objects, MACHOs, the whimsically named counterpart to other dark matter candidates called WIMPs.
Participation in LSST quickly centered on the Lab’s expertise in large optics, built over decades of developing the world’s largest laser systems.
Starting in 2002, LLNL optical scientist Seppala, who helped design the National Ignition Facility, made a series of design improvements that led to the 2005 baseline design.
This consisted of three mirrors, the two largest in the same plane so they could be fabricated from the same piece of glass. The design includes three large lenses and a set of six filters that define the color of the images recorded by the 3.2-gigapixel camera detector.
Construction on LSST started in 2014 on El Peñon, a peak 8,800 feet high along the Cerro Pachón ridge in the Andes Mountains. It’s located 220 miles north of Santiago, Chile.
Financial support for LSST comes from the National Science Foundation, the U.S. Department of Energy’s Office of Science, and private funding raised by the LSST Corporation.
The National Science Foundation-funded LSST Project Office for construction was established as an operating center under the management of the Association of Universities for Research in Astronomy. The DOE-funded effort to build the LSST camera is managed by the SLAC National Accelerator Laboratory.
The camera system for LSST, including the three lenses and six filters designed by LLNL researchers and built by industrial partners, will be shipped to Chile in early 2021.