The National Science Foundation has awarded the GMTO Corporation — the organization overseeing construction and management of the $1bn Giant Magellan Telescope (GMT) – a grant of $17.5m over the next three years to accelerate the construction of the 25 m-wide telescope.
The GMT will be located at Las Campanas in Chile’s Atacama Desert and is on-track for first light in 2029. Hard rock excavation at the site is complete and in October 2019 the GMTO signed a $135m contract with German company MT Mechatronics and US-based Ingersoll Machine Tools in Illinois to design, build, and install the GMT’s telescope structure. This is set to be delivered to the Chilean site at the end of 2025.
[The NSF award] will enable us to accelerate our progress on critical components of the telescope
Robert Shelton
The GMT will have seven circular mirrors, each 8.4 m in diameter. When put together, they will create a telescope equivalent to one mirror 25.4 m wide. Two of the mirrors are complete and in storage in Arizona, while three are in various stages polishing. The final two haven’t been started yet, but the sixth mirror will be cast in early March 2021.
Acting as one
Each primary mirror is flexible, but they must remain in a precise shape for all seven to function together as one. “The mirror itself is supported, like on a bed of nails, where we have about 160 actuators behind each of these mirrors,” says GMTO project manager James Fanson. “We measure the shape of these mirrors and we adjust them every 30 seconds.” The NSF grant provides the funding to test a full-size primary mirror and actuator system, and adds Fanson, “to demonstrate we can control the primary mirrors the way we need to.” Giant Magellan Telescope Organization president resigns
Each GMT primary mirror reflects light to a corresponding 1 m-diameter secondary mirror with 675 actuators, which alter its shape every millisecond to counteract Earth’s atmospheric blurring effect. With the NSF grant, the GMTO will also build a portion of one of the secondary mirror systems. The grant also provides funding to build a laboratory-bench test to simulate the mirrors, actuators, disturbance sources, and that the seven primary mirrors can all phase together as one — technology not used before.
“One of the areas of great emphasis the team has had from the beginning is to tackle the riskiest, most difficult questions early on to make sure they can be surmounted,” says GMTO president Robert Shelton, who adds that the NSF award will “enable us to accelerate our progress on critical components of the telescope”.
