TMT Is A-OK

Above: From left, the five-meter Hale, ten-meter Keck, and Thirty Meter Telescope mirrors to scale.

The Thirty Meter Telescope, or TMT, has passed its conceptual design review by an independent panel of experts. Now in detailed design, the TMT will be the world’s largest telescope. It consists of a primary mirror with 738 individual 1.2-meter segments that span 30 meters in total, three times the effective diameter of the current largest telescopes. All of the segments will be under exquisite computer control so that they work together as a single mirror. 

The review panel evaluated all aspects of the project, including optical design, telescope structure, control systems, science instrumentation, site testing, and management and cost-estimation procedures. The panel praised in particular the adaptive optics technology that will allow the TMT to reach the “diffraction limit,” seeing things the way a telescope in outer space would see them. Much of the TMT’s scientific work will be done in the infrared, where the diffraction limit is easier to attain, young stars and galaxies are to be found, and the opportunities for new discoveries are abundant.

TMT’s eight scientific instruments, also in the detailed-design phase, are huge in comparison to current astronomical instruments, and equivalently more complex. Each one is the size of a school bus or larger, and they rest on two basketball-court-sized platforms on either side of the telescope. The biggest technical challenges are posed by the Planetary Formation Instrument, which employs “extreme” adaptive optics in an effort to see other planets directly, rather than infer their presence by their effects on their stars, as is currently done.

Says Richard Ellis, Caltech’s Steele Family Professor of Astronomy, “We’ll decide in mid-2008 where to build the telescope and then plan to start construction in early 2009.” Science operations are slated to begin in 2016. The TMT project is studying five sites in Chile, Hawaii, and Mexico, and the project’s offices are located at CIT², formerly St. Luke’s Hospital, in Pasadena, where the design review was carried out.

The TMT is a collaboration between Caltech, the University of California, the Association of Universities for Research in Astronomy, Inc. (AURA), and the Association of Canadian Universities for Research in Astronomy (ACURA), with significant instrument-design work being done by industry and by university teams.  TMT’s design and development phase has a budget of $64 million, including $35 million in private-sector contributions from the Gordon and Betty Moore Foundation. —RT