NASA SP-2009-1704. Steven J. Dick, Editor. Based on a symposium held on October 28-29, 2008 at NASA. Scholars turn a critical eye toward NASA's first 50 years.

Ensuring a Sustainable World
We are on the cusp of a 21st century Age of Discovery - about the Earth, about the solar system, about ourselves and our place in the cosmos - with new opportunities to address age-old challenges, as well as to meet emerging ones. While advancing into space is not the answer to these challenges, it can be a significant and vital part of an answer, providing benefits that other answers cannot.
With a thoughtful program of space activities we can ensure a sustainable world with abundant energy and resources, a high standard of living, and unprecedented opportunity for all. However, to become a widely held vision that we must pursue now, rather than just interesting ideas for some distant time, we need to see space as integral to addressing societal issues. This book shows a way to do that.
There are abundant opportunities in space, but the only way to utilize them is to go there. As our ancestors crossed thresholds to inhabit the Earth, we can cross the threshold to become a space-faring civilization, and realize the benefits of those efforts. Space is only 100 km (62 miles) away, you just need to look up.
What people are saying:
"Crossing the Threshold is a carefully considered, insightful narrative that should interest anyone and everyone who cares about the future of spaceflight." - Homer Hickam, author of Rocket Boys/October Sky
"Crossing the Threshold is a NASA veteran's thoughtful and considered look at the value of space travel and exploration, not only for satisfying humanity's seemingly unquenchable thirst for adventure and knowledge but also for preparing and positioning us technically to begin to solve some of the greatest problems facing us on Earth." - Henry Petroski, Aleksandar S. Vesic Professor of Civil Engineering and Professor of History, Duke University, author of The Essential Engineer: Why Science Alone Will Not Solve Our Global Problems
Crossing the Threshold "is very impressive for the range of ideas and technical specifics." - Felix Godwin, author of The Exploration of the Solar System.

The invention of the semiconductor laser along with silica glass fiber has enabled an incredible revolution in global communication infrastructure of direct benefit to all. Development of devices and system concepts that exploit the same fundamental light-matter interaction continues. Researchers and technologists are pursuing a broad range of emerging applications, everything from automobile collision avoidance to secure quantum key distribution. This book sets out to summarize key aspects of semiconductor laser device physics and principles of laser operation.

The Ptolemaic system of the universe, with the earth at the center, had held sway since antiquity as authoritative in philosophy, science, and church teaching. Following his observations of the heavenly bodies, Nicolaus Copernicus (1473-1543) abandoned the geocentric system for a heliocentric model, with the sun at the center. His remarkable work, On the Revolutions of Heavenly Spheres, stands as one of the greatest intellectual revolutions of all time, and profoundly influenced, among others, Galileo and Sir Isaac Newton.

This book addresses a variety of topics within the growing discipline of Archaeoastronomy, focusing especially on Archaeoastronomy in Sicily and the Mediterranean and Cultural Astronomy. A further priority is discussion of the astronomical and statistical methods used today to ascertain the degree of reliability of the chronological and cultural definition of sites and artifacts of archaeoastronomical interest. The contributions were all delivered at the XVth Congress of the Italian Society of Archaeoastronomy (SIA), held under the rubric "The Light, the Stones and the Sacred" - a theme inspired by the International Year of Light 2015, organized by UNESCO. The full meaning of many ancient monuments can only be understood by examining their relation to light, given the effects that light radiation produces in "interacting" with lithic structures. Moreover, in addition to manifestations of the sacred through the medium of light (hierophanies), there are many ties between temples, tombs, megalithic structures, and the architecture of almost all ages and cultures and our star, the Sun. Readers will find the book to be a source of fascinating insights based on synergies between the disciplines of archaeology and astronomy.

This book on space geodesy presents pioneering geometrical approaches in the modelling of satellite orbits and gravity field of the Earth, based on the gravity field missions CHAMP, GRACE and GOCE in the LEO orbit. Geometrical approach is also extended to precise positioning in space using multi-GNSS constellations and space geodesy techniques in the realization of the terrestrial and celestial reference frame of the Earth. This book addresses major new developments that were taking place in space geodesy in the last decade, namely the availability of GPS receivers onboard LEO satellites, the multitude of the new GNSS satellite navigation systems, the huge improvement in the accuracy of satellite clocks and the revolution in the determination of the Earth's gravity field with dedicated satellite missions.

Robert Grosseteste (1168/75-1253), Bishop of Lincoln from 1235-1253, is widely recognized as one of the key intellectual figures of medieval England and as a trailblazer in the history of scientific methodology. Few of his numerous philosophical and scientific writings circulated as widely as the Compotus, a treatise on time reckoning and calendrical astronomy apparently written during a period of study in Paris in the 1220s. Besides its strong and long-lasting influence on later writers, Grossteste's Compotus is particularly noteworthy for its innovatory approach to the theory and practice of the ecclesiastical calendar-a subject of essential importance to the life of the Latin Church. Confronting traditional computistical doctrines with the lessons learned from Graeco-Arabic astronomy, Grosseteste offered his readers a critical and reform-oriented take on the discipline, in which he proposed a specific version of the Islamic lunar as a substitute for the failing nineteen-year cycle the Church still employed to calculate the date of Easter. This new critical edition of Grosseteste's Compotus contains the Latin text with an en-face English translation. It is flanked by an extensive introduction and chapter commentary, which will provide valuable new insights into the text's purpose and disciplinary background, its date and biographical context, its sources, as well as its reception in later centuries.

A contemporary of Galileo and a forerunner of Isaac Newton, Johannes Kepler (1571-1630) was a pioneering German scientist and a pivotal figure in the history of astronomy. This colorful, well-researched biography brings the man and his scientific discoveries to life, showing how his contributions were every bit as important as those of Copernicus, Galileo, and Newton. It was Kepler who first advocated the completely new concept of a physical force emanating from the sun that controls the motion of the planets--today we call this gravity and take it for granted. He also established that the orbits of the planets were elliptical in shape and not circular. And his three laws of planetary motion are still used by contemporary astronomers and space scientists. The author focuses not just on these and other momentous breakthroughs but also on Kepler's arduous life, punctuated by frequent tragedy and hardships. His first wife died young, and eight of the twelve children he fathered succumbed to disease in infancy or childhood. He was frequently caught up in the religious persecutions of the day. His mother narrowly escaped death when she was accused of being a witch. Intermingling historical and personal details of Kepler's life with lucid explanations of his scientific research, this book presents a sympathetic portrait of the man and underscores the critical importance of Kepler's discoveries in the history of astronomy.

Pulsar timing is a promising method for detecting gravitational waves in the nano-Hertz band. In his prize winning Ph.D. thesis Rutger van Haasteren deals with how one takes thousands of seemingly random timing residuals which are measured by pulsar observers, and extracts information about the presence and character of the gravitational waves in the nano-Hertz band that are washing over our Galaxy. The author presents a sophisticated mathematical algorithm that deals with this issue. His algorithm is probably the most well-developed of those that are currently in use in the Pulsar Timing Array community. In chapter 3, the gravitational-wave memory effect is described. This is one of the first descriptions of this interesting effect in relation with pulsar timing, which may become observable in future Pulsar Timing Array projects. The last part of the work is dedicated to an effort to combine the European pulsar timing data sets in order to search for gravitational waves. This study has placed the most stringent limit to date on the intensity of gravitational waves that are produced by pairs of supermassive black holes dancing around each other in distant galaxies, as well as those that may be produced by vibrating cosmic strings. Rutger van Haasteren has won the 2011 GWIC Thesis Prize of the Gravitational Wave International Community for his innovative work in various directions of the search for gravitational waves by pulsar timing. The work is presented in this Ph.D. thesis.