Two US-led groups are planning 30-meter-class optical-IR telescopes, each with a price tag approaching $1 billion. Neither project has yet raised enough private money to cover the full cost, and both hope for public funding. But before getting on board, NSF wants to see what priority the astronomy community places on extremely large telescopes in the next astronomy and astrophysics decadal survey, which will be completed over the next 18 months or so.
The Thirty Meter Telescope (TMT) design, an extension of the technology used in the Keck telescopes, consists of 492 1.4-meter hexagonal mirror tiles. The rival Giant Magellan Telescope’s (GMT’s) primary mirror would be made from seven 8.4-meter circular segments. It would have a diffraction aperture of 24.5 meters but, because of the gaps between the segments, a collecting area equivalent to a 22-meter telescope. “The two designs are sophisticated. It’s very likely that we will actually get...
