The Giant Magellan Telescope will be three times the size of any ground-based optical telescope built to date.

The GMT and the Thirty Meter Telescope (TMT) are a part of the US Extremely Large Telescope Program (US-ELTP).

The Giant Magellan Telescope is designed to have a resolving power ten times greater than the Hubble Space Telescope.

The Giant Magellan Telescope's primary mirror comprises seven 8.4 meter mirror segments. They will push to the diffraction-limit of imaging which is a limitation based on physics. They will phase these primary mirror segments so that they behave as a monolithic mirror. Once phased, we must then correct for Earth's turbulent atmospheric distortion. This will get close to the image resolution of placing a large telescope in phase.

The NSF grant enables the GMT to build two phasing testbeds that will allow engineers to demonstrate, in a controlled laboratory setting, that its core designs will work to align and phase the telescope's seven mirror segments with the required precision to achieve diffraction-limited imaging at first light in 2029. It also enables the partial build and testing of a next-generation Adaptive Secondary Mirror (ASM), which is used to perform the primary mirror phasing and atmospheric distortion correction.

One of the main goals will be to look for faint signs of life on distant exoplanets.