Giant Telescope Construction Viewed Through an Industrial Lens
EtherCAT and PC-based control are specified for automation of the Giant Magellan Telescope, including more than 3,000 motion axes and site-wide fieldbus infrastructure
Once installed at Las Campanas Observatory in the Chilean Andes, the Giant Magellan Telescope (GMT) will introduce incredible opportunities for the astrophysics and cosmology research communities. The telescope design boasts an angular resolution 10 times greater than that afforded by the Hubble Space Telescope by combining seven mirrors into a singular optical system with a total diameter of 25 meters. When the GMT goes online in 2029, it will represent the next evolution of the giant ground-based telescopes that became possible in the 1990s with the advent of new industrial control technologies. However, telescope technology has changed significantly since those days through advanced computer architectures, modern programming languages, real-time industrial protocols, web-based standards and specialized controllers.
These advances will enable the GMT to capture images of astronomical objects sharper than currently possible by reducing distortions introduced by the terrestrial atmosphere. It will also allow scientists to peer back into the first one billion years after the Big Bang, according to former GMTO Corporation Vice President Dr. Patrick McCarthy. As an astronomer, McCarthy researches this “first light” epoch when stars, galaxies and primordial black holes first formed. Although the GMT will depend on high-tech automation systems to accomplish complex feats, its purpose remains clear. “The GMT’s mission is to provide the tools that will enable future generations of astronomers to make great discoveries and push back the frontiers of our knowledge about the universe,” says McCarthy.
With these extreme capabilities and requirements, the GMT may seem to have little in common with general production machinery and factory automation. In fact, scientists and engineers working on similar telescope projects have traditionally built their own automation solutions using custom control components. However, the team building the GMT sees this differently, explains GMTO Senior Electronics Engineer José Soto: “We want to change the historical method of treating telescopes as special and totally unlike other automated systems. Future-facing industrial control solutions have the power to solve many problems we face today in astrophysics.”
The long road to Las Campanas
From GMTO headquarters in Pasadena, California, it takes about 24 hours of travel to reach the summit at Las Campanas Observatory. The site is optimal for astronomy due to its elevation and documented history of favorable weather, minimal light pollution and smooth airflow, which reduces image distortion due to inhomogeneities of heat and turbulence, McCarthy explains. “Very few places on Earth meet those requirements, but this area was designated as one back in the 1960s, when a group of astronomers with a few burros were traveling around the Andes to find good locations to build telescopes,” he says. “As a result, the Carnegie Institution for Science in Washington, D.C., purchased about 60 square miles of this mountainous area in the mid-1960s, and since then multiple telescopes have been built there. Eventually, Carnegie became one of the 12 founding partner institutions of GMTO.”
While the journey to the summit is long, the GMT journey from concept to completion has also required perseverance. Since the GMTO project started in the early 2000s, engineers, scientists and administrators have been working to design the physical structures and systems of the telescope, according to GMTO Project Manager Dr. James Fanson. Crews have been working to shape mirrors at the University of Arizona’s Richard F. Caris Mirror Laboratory since 2005, and GMTO broke ground on Las Campanas peak in 2015, says Fanson, who previously led telescope and astrophysics projects at NASA’s Jet Propulsion Laboratory. “Since 2015, we have built offices, construction infrastructure and residence, dining and recreation facilities to accommodate up to 200 construction workers and GMTO staff. These have been close to capacity during our recent activities,” Fanson says.
Specifying automation and controls components for the GMT also required careful consideration due to the real-time communication and control requirements, especially considering the system will possess more than 3,000 axes of motion. Beyond rotating the telescope’s 22-story-tall enclosure, the flexible mirrors must be moved with utmost precision to implement adaptive optics and achieve the highest possible image resolution. One example is the active optics system, which requires integration of 170 pneumatic actuators per primary mirror to support the mass of each mirror. The engineering team identified the need for automation and controls components that were powerful now, but would also support future advances in technology, explains Soto: “Since these projects take a long time we must account for obsolescence in every aspect. The most effective method of fighting obsolescence is standardizing on proven industrial technologies.” These factors led GMTO to standardize many specifications for the control system using industrial standards such as are found in solutions offered by Beckhoff Automation.
Looking to PC-based automation solutions
GMTO engineers began exploring industrial automation and controls including automation and control solutions offered by Beckhoff to satisfy the team’s desire to implement fieldbus technologies to a greater degree than other telescopes have previously achieved. The engineers examined multiple industrial Ethernet networks, but found EtherCAT to provide a flexible topology and scalability, along with the ability to incorporate up to 65,535 EtherCAT devices in one network, that matched the system specification of the GMT.
“EtherCAT will be embedded in nearly every GMT telescope system — from the primary mirrors to the atmospheric dispersion compensator, the enclosure, mount and even the building automation in the facilities,” Soto says. According to GMTO Engineer Hector Swett, Safety over EtherCAT (FSoE) also offered impressive functionality for the telescope’s interlock and safety systems. FSoE provides GMT with safety-rated, TÜV-certified communication over standard EtherCAT networks, numerous options for distributed TwinSAFE I/O modules and integration with the Beckhoff engineering environment and Industrial PCs (IPCs).
Certain current GMT specifications recommend multiple PC-based controllers that could be fulfilled by Beckhoff solutions. The interlock and safety system relies on many safety controllers, DIN-rail-mounted CX9020 Embedded PCs working in conjunction with EL6910 TwinSAFE Logic I/O modules. These interface with each other through FSoE via EtherCAT Automation Profile (EAP) to implement safety functions as required by the hazard analysis, Swett says. Beckhoff CX2020 Embedded PCs with single-core 1.4 GHz Intel® Celeron® processors are used in the GMT Hardware Development Kit, which was built for the project’s partners to develop instruments for the telescope. In addition to performance, the rugged design of these controllers remains key. “Observatories located in remote mountaintops experience harsh conditions that these IPCs can easily withstand,” Soto explains. “Also, the embedded PCs offered great scalability and small form factors, which saves valuable space in control cabinets.”
TwinCAT 3 automation software from Beckhoff has offered a key platform to test devices, and it is specified for control of the structures around the telescope. “The PC-based controller for the telescope’s enclosure will run TwinCAT directly,” Swett says. “It also provides the real-time capability to interface this massive application with the observatory control system via OPC UA.” Exemplifying system openness, TwinCAT supports programming of control logic in many languages, such as those included in IEC 61131-3, including object-oriented extensions, and the computer science languages offered in Microsoft Visual Studio®. The software can automatically scan and configure third-party devices over ADS and EtherCAT, providing an optimal platform for tasks from sensing to motion control.
Because the telescope will have thousands of axes of motion, dependable motors and drives will be crucial in the final configuration. Soto finds the capabilities of Beckhoff AM8000 Servomotors impressive and sees them as a serious contender for multiple areas throughout the telescope. “When our integrator teams begin to commission the telescope, they will very likely use AM8000 Servomotors, for example, in the atmospheric dispersion compensator or the GIR (Gregorian Instrument Rotator) that will move all instruments attached to the Cassegrain focus,” Soto explains. During rigorous testing, GMTO engineers have noted the extreme flexibility of the servomotors and other Beckhoff hardware and software and believe these solutions will aid in constructing one of the world’s most advanced telescopes with industrial, off-the-shelf components.
New technologies and creative ideas redefine our universe
After decades in the making, the end goal is coming into focus for GMTO, and the reliable automation and controls components specified for the telescope add clarity. EtherCAT first led the GMTO engineers to Beckhoff, and it remains foundational to the telescope’s control architecture design, Soto explains: “Using EtherCAT as the GMT fieldbus enables real-time communication down to the I/O-level. We have achieved cycle times of 2 kHz, which allows enough bandwidth to close the loop on a range of subsystems, expanding our control and networking abilities significantly.” Compact EtherCAT I/O modules and Embedded PCs save space in control cabinets, and because the PC-based controllers can be located at a distance from the I/Os, this reduces heat dissipation. “Reducing heat is a very big deal for the GMT,” Swett adds. “Heat makes the air more turbulent inside the enclosure, and turbulence distorts images as the light travels through the air. This distributed I/O architecture helps us prevent that.”
As GMTO works toward the goal to provide tools for future generations, the Beckhoff sales and support engineers have offered assistance and advice along the way, says Swett. This help, combined with rigorous testing and dedication to finding the right solutions, has made the implementation of industrial automation and controls components a reality. Apart from its size and complexity, Soto says, the GMT has one major difference between other machinery that uses similar off-the-shelf components: “This is a one-time project. It is not one of many machines coming down a production line. So the main challenges are to perfect the design and select the right products for the telescope the first time.”
In a decade, this process of observation and discovery will not belong to the engineers designing and building the GMT, but to the astrophysicists and cosmologists using it to explore the cosmos. Because of these new capabilities, McCarthy sees this as a very exciting time to be working in the field. “New tools enable voyages into the unknown — and the ‘unknown-unknown.’ This refers to the things we cannot anticipate at all and things that we think we know that ultimately turn out to be wrong,” he says. “With this in mind, we have designed the GMT with potential for future development. This will offer researchers the flexibility to bring their own creative ideas when using the telescope to make great discoveries that we have not yet imagined.”
A global vision
The Giant Magellan Telescope project is an international consortium of 12 founding institutions. These include Arizona State University, Astronomy Australia Limited, Australian National University, Carnegie Institution for Science, FAPESP — The São Paulo Research Foundation, Harvard University, Korea Astronomy and Space Science Institute, Smithsonian Institution, Texas A&M University, The University of Texas at Austin, University of Arizona and University of Chicago. By supplying funding for the construction and operation of the telescope, these organizations will receive access for their researchers to use the Giant Magellan Telescope after a peer review process to prioritize projects.
Are you interested in enhancing your research technology and machine designs with PC-based automation? Contact your local Beckhoff sales engineer today.
James Figy is the Senior Content Specialist for Beckhoff Automation LLC.
A version of this article previously appeared in Design World.