Ever since Galileo first turned his telescope to Jupiter over 400 years ago and saw the orbiting Jovian moons, telescopes, the tools of observational astronomy, have transformed our understanding of the universe and our place in it. Within the last 100 years, successive generations of telescopes have revealed the enormity and complexity of the universe, and have provided the clues that inspire the quest to piece together its origin and history.
In 1654, Bishop Lightfoot concluded that "heaven and earth, center and circumference, were created together, in the same instant, and that this work took place on the twenty third of October 4004 BC, at nine o'clock in the morning." Although we may be startled by the confidence of this conclusion, Bishop Lightfoot was a man of great integrity, and there was then scant evidence to contradict such a declaration. It wasn't until the latter part of the nineteenth century that Charles Darwin postulated that evolution required much more than 40 million years to evolve complex organisms, only to be told by the physicist Lord Kelvin that he had definitively proved the Earth could be no older than between 20-40 million years old.
It was not until the twentieth century-with the development of modern telescopes, coupled with an evolving understanding of stellar evolution and the discovery of radioactive decay-that these first fiercely fought scientific contradictions began to be resolved as we glimpsed the first hints of the "unimaginable timescales" involved in the Earth and its solar system's history. Today, just a little under 100 years after the American physicist Bertram Boltwood first measured the radioactive decay in rocks and realized the appropriate unit for measuring ages was not millions of years but billions of years, astronomers using telescopes both on the ground and orbiting in space have established that a clock has been ticking in this universe for at least the last 13-15 billion years.
At the beginning of the next decade, two powerful new telescopes will be completed: The James Webb Space Telescope (JWST) and the Atacama Large Millimeter Array (ALMA). These new tools will enable us to carry on the quest to understand our origins and ultimate fate. Together, they will image the redshifted light from the first stellar systems to appear after the big bang and probe the cold, dense molecular clouds where stars and their associated planetary systems take form. Although JWST and ALMA will enable fundamental advances in understanding the origins of galaxies, stars, and planets, a complete appreciation of both the phenomenology and basic physical processes that underlie these defining events will be impossible without a next generation ground-based optical and infrared telescope-that is, having sensitivity sufficient to probe the chemistry and kinematics of emerging structures in the early universe, and sensitivity and image quality matched to the challenge of deciphering when, where, and how often planets form.
The critical need for a next generation ground-based telescope was recognized by the National Research Council's (NRC) Astronomy and Astrophysics Survey Committee (AASC), which recommended the construction of a 30-m, filled-aperture, segmented-mirror optical and infrared telescope-a Giant Segmented Mirror Telescope (GSMT)-as its highest priority for ground-based astronomy. When complete, GSMT will have 10 times the power of the largest telescopes currently in operation.
In its decadal report, the NRC urges an aggressive design effort over the next few years to identify and solve the technical challenges of this ambitious program at affordable cost, and to complete construction of a 30-m class telescope in time to begin operations contemporaneously with JWST and ALMA. The AASC also expressed the strong belief that a GSMT should be available competitively to all US astronomers, and recommended significant federal investment targeted at forming a partnership involving the US national observatory and either private observatories in the US or international collaborators.
TOWARD A GSMT
In response to the recommendations of the decadal survey, the Associated Universities for Research in Astronomy (AURA) accelerated its ongoing investments in studying next generation telescope concepts and formed a New Initiatives Office (NIO). The NIO was created specifically to explore the technical hurdles that must be overcome to build a GSMT that provides the performance needed to meet the scientific requirements of the next decade. To meet this challenge, NIO was able to draw from the strengths inherent in the two ground-based institutions AURA manages: the National Optical Astronomy Observatory (NOAO) and the International Gemini Observatory. NOAO contributes a 40-year experience base in designing, instrumenting, and operating frontier astronomical facilities for the US community, while Gemini contributes an international dimension and the systems and design expertise that led to the successful completion of the twin 8-m diameter Gemini telescopes and their sophisticated complement of instruments.
Over the past year, the NIO core group of scientists and engineers has worked with members of the US and international communities to:
- Understand the key science problems confronting modern astrophysics at the start of the twenty-first century, and the role of a 30-m ground-based optical/infrared telescope in addressing them;
- Develop and quantify the key performance requirements of such a telescope;
- Gain a detailed understanding of the technology challenges and interrelated system issues that must be overcome in building GSMT by developing a conceptual point design of a 30-m telescope and the required instrumentation matched to these performance requirements; and
- Study design, technology, and implementation issues common to the next generation of ground-based telescopes.
This "book" describes the initial results of these coordinated efforts and outlines the next steps toward achieving the shared goal of providing broad community access to a 30-m GSMT early in the next decade. Its key conclusions are captured in the following Executive Summary.