Issue 7 • January, 2007
Thirty Meter Telescope

Project Manager's Corner: The Next Steps
  Gary Sanders

The figure shows four copies of TMT on a mountain summit. This arrangement evokes the placement and setting of the two Keck telescopes in the Keck Interferometer on Mauna Kea, or the striking array of four unit telescopes that the European Southern Observatory operates on Cerro Paranal as the VLTI. These are powerful interferometric tools for astronomy. The figure suggests a TMTI, a stupendous combination of four TMT telescopes providing amazing resolution capability. Alas, while visually exciting, a TMTI would be prohibitively expensive.

The figure, courtesy of M3 Engineering, actually represents something more mundane but still very important. It is a trade study comparing four arrangements of summit buildings with varying facility arrangements and roof heights, placed next to our enclosure with its ventilation openings. It is input to aerodynamic modeling of the flow across these structures. What is notable about this is that it marks a kickoff of the next, and more detailed, phase of TMT design.

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TMT Science Workshop

Planning has begun for a 3-day workshop on "Science in the Era of TMT" to be held this summer. The workshop will bring together scientists from the TMT partner countries and around the world to share and develop concepts and ideas for science programs enabled by extremely large telescopes. The workshop will be held at the Beckman Center on the campus of the University of California at Irvine, July 23-25. Further details will be posted on the TMT website.

Science Nugget—Unveiling a Supermassive Black Hole at the Center of Our Galaxy

Astronomers are presently closing in on proof that one of the most enigmatic objects in our Universe - a supermassive black hole - lurks at the heart of our own galaxy, the Milky Way. Over the last decade, near-infrared diffraction-limited imaging with 10 meter class telescopes has revealed that several of the stars near the Galactic center (GC) are moving on elliptical trajectories with velocities as large as 12,000 km/sec, a few percent the speed of light (see Figure 1). These motions can only be explained if the stars are orbiting a central dark mass 4 x 106 times more massive than the Sun, confined within a volume only 45 AU on a side. These measurements provide the most definitive evidence for the existence of a supermassive black hole (BH), not only at the center of our galaxy, but more broadly of any galaxy in our Universe (Ghez et al. 2003, 2005; Schodel et al. 2002, 2003). Because the center of the Milky Way is 100 times closer than the next closest galaxy, the GC presents a unique opportunity to study a supermassive BH and its environs in much more detail than is possible in any other galaxy.

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Technology Nugget—Controlling all those Segments, Part 2: Sensors

In the previous edition of Technology Nugget we introduced the complex system responsible for maintaining the overall shape of the TMT primary mirror which consists of 492 segments. We call segment assembly with three actuators (illustration)this system the M1 Control System (M1CS) and it consists of 1,476 actuators, 2,772 sensors, thousands of electronic assemblies, and many sophisticated control algorithms (software). The system that is used to determine the proper "set-points" for the M1CS using starlight is known as the Alignment and Phasing System (APS). We can think of the M1CS as a system that "stabilizes" the 492 mirror segments and the APS as the system that "aligns" the 492 segments by determining the set-points for use by the M1CS. In particular, last month we described the actuators that are responsible for moving the segments. In this edition of Technology Nugget we will discuss the M1CS edge sensors. The edge sensors provide very precise measurements of the height differences between adjacent segments.

Recall from our discussion on actuators that motions within the plane of each segment are minimized passively by a complex structure called a Segment Support Assembly (SSA). The remaining out-of-plane motions of each segment are controlled by three actuators symmetrically positioned so as to enable motion of piston, tip, and tilt. The sensor height measurements and the "set-points" determined by the APS are utilized by a software control algorithm to generate actuator commands. The actuator commands are calculated to position the 492 individual segments so as to imitate a nearly perfect monolithic mirror.

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Q & A with Chuck Steidel

Chuck Steidel is the DuBridge Professor of Astronomy at Caltech, and has been involved in thinking about science and instruments for 30m telescopes since 1998; he has served as one of the co-chairs of the Science Advisory Committee for TMT since the beginning of the project.

Chuck sat down for an interview with Doug Isbell recently to discuss the TMT's exciting potential breakthroughs in the understanding of galaxy formation and evolution.

Download Chuck Steidel Interview [11:09 min. 10.2 MB MP3]

Focus On - Europe Moves Forward

Our European colleagues are not idle. Indeed, they have just taken a major stride towards their own extremely large telescope (ELT). We pointed to news coverage of the start of their project design (Europe plans giant eye on the sky) and (Extremely Large Telescope could reveal secrets of life, the universe and everything) in our August Newscast. We were particularly pleased to see many potential design features that were similar to features of TMT, and we have looked forward to cooperative development and communication. Now Europe has moved farther and completed several steps leading to a design concept that will guide their next steps in development. See The Rise of a Giant; ESO Council Gives Green Light to Detailed Study of the European Extremely Large Telescope.

Partner News
  TMT Partner, AURA, Steps Back from TMT and Takes on a New Role in our Program

The original TMT partnership was formed between University of California, Caltech, the Canadian ACURA consortium, and AURA. AURA provided access to TMT for the US publicly funded astronomy community. With the release of the NSF Division of Astronomy Senior Review in October, NSF has asked AURA to take on a new role. NSF has asked that AURA/NOAO act as NSF's "Program Manager" for the GSMT Technology development effort at a national level in a manner similar to the role played by NASA's major Centers for the development and operations of various space missions. For those of you who do not follow the acronyms in this field, GSMT stands for Giant Segmented Mirror Telescope, a generic label used for any very large telescope being designed to fulfill the goals of the 2001 decadal survey of astronomy. There are two such programs in the US, the Carnegie Observatories GMT project, and our own TMT. AURA has been a partner in TMT, but has supported NSF in managing the parallel and balanced funding by NSF of both projects. Under the new arrangement, AURA will take a more management oriented role, coordinating the continuing support by NSF of both projects. TMT looks forward to continuing to work closely with AURA and NSF to define the TMT technology base and design and we appreciate the continued support of NSF in fulfilling important national needs.

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TMT is supported in the United States by the Gordon and Betty Moore Foundation and the US National Science Foundation. Canadian funding is provided by the Canada Foundation for Innovation, the Ontario Ministry of Research and Innovation, the National Research Council of Canada, the Natural Sciences and Engineering Research Council, and the British Columbia Knowledge Development Fund.

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