US ELT Program: GMT Design and Development

The Giant Magellan Telescope (GMT) is a next-generation “extremely large telescope” that is to be built in Chile, with first observations of the southern skies anticipated in the mid-to-late 2030s. With this award, the National Science Foundation will support development of key technologies needed to ensure the telescope obtains the sharpest images possible. At the heart of the GMT are seven 8.4-meter diameter mirrors. These must be aligned with seven smaller mirrors, each 1-meter in diameter, mounted at the top of the telescope. This precise alignment, or “phasing”, requires very careful design and testing of a range of cutting-edge technologies. The award will support this crucial development work. The award will also support a workforce development program and research into an informal education program. GMT will plan a summer program of activities, based on the University of Texas at Austin’s existing Texas Astronomy Undergraduate Research Experience for Under-represented Students (TAURUS) Program, that will target underrepresented communities. Working with the San Francisco Exploratorium, GMT will also explore new ways of developing exhibits that are better suited to a diverse audience, ideas that could be used in a future travelling GMT exhibition. The project will focus on three specific technical risk-reduction activities. The primary mirror (M1) active optics system will be tested by installing one of the recently completed M1 segments in a Primary Mirror Test Cell, to demonstrate active optics control of the mirror surface wavefront error using the optical metrology tower at the University of Arizona’s Richard F. Caris Mirror Lab. The project will also build an Adaptive Secondary Mirror Phasing Testbed (ASM PTB) and will use this to demonstrate ASM segment position sensing and control. The PTB will include a metrology frame of reference for the ASM first article and will confirm position sensor performance. Finally, the team will also develop a Laser Tomography Adaptive Optics Wavefront Sensor (LTWS) prototype to address potential design risk features identified during the preliminary design phase, prototyping a single channel Shack-Hartmann Sensor, and testing the dynamic performance of the sensor motion stages and cable wrap design concepts. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.