Science and Security in Sharp Focus
THE military and economic security of nations has always gone hand-in-hand with the advance of basic science. In her highly acclaimed book Longitude, Dava Sobel describes how the fortunes of navies and nations suffered for the lack of a precision chronometer that would enable mariners to determine their longitude as accurately as the sextant determined their latitude. Kings and governments invested fabulous sums of money to discover a solution. In so doing, they financed some of the most remarkable discoveries in astronomy and science from the 15th to 19th century, including the first accurate determination of the speed of light based on the eclipse of the Jovian moons, by Olaf Roemer in 1675.
The intertwining and leveraging of mission-driven and exploratory science—exemplified by the problem of measuring longitude—are hallmarks of Lawrence Livermore. The Laboratory’s program in adaptive optics technology is a perfect example of this interplay. The adaptive optics team at Livermore, arguably the best in the world, supports a wide spectrum of national security applications, and its work regularly appears on the covers of prestigious journals such as Science.
What is adaptive optics? The familiar twinkling of a star at night is due to density fluctuations in the atmosphere that distort the wavefront of starlight, thus changing its optical path as the light travels to our eyes. Adaptive optics uses a reference object—a real or artificial star—that ought to be a stationary point in the field of view, to correct the wavefront in real time. With the reference object corrected, other sources in this field of view, such as galaxies or planets, are also transformed from blurry blobs into ultrasharp images.
In the early 1980s, Livermore physicist Claire Max and Will Happer of Princeton University wrote a then-classified paper setting out the principle of the “laser guide star,” by which a laser beam would fluoresce the sodium layer in the upper atmosphere. This technique would allow astronomers to place a reference star anywhere at will. Max, who now serves as director of the Center for Adaptive Optics at the University of California (UC) at Santa Cruz, pioneered the application of this technique in astronomy and later won the E. O. Lawrence Award. Today, virtually every large telescope in the world has or will have laser guide star capability.
Livermore researchers have applied adaptive optics technology to a range of mission areas. The National Ignition Facility simply would not work without adaptive optics correctors to preserve a near-diffraction-limited spot from each of its beams. Laboratory expertise in this technology led to the Coherent Communication, Imaging, and Tracking Program for the Defense Advanced Research Projects Agency and to high-average-power lasers developed for the Army. The Laboratory’s adaptive optics team has carried out pioneering work in retinal vision sponsored by both the Department of Energy and the National Institutes of Health. In 2002, a collaboration involving Livermore and UC Santa Cruz was awarded a coveted National Science Foundation (NSF) Science and Technology Center to develop adaptive optics for applications in astronomy and medicine. All the while, front-cover astronomy flourished, accompanied by prestigious awards and recognition for Livermore scientists and engineers.
The article Extending the Search for Extrasolar Planets explores a project that takes a major leap in adaptive optics to directly image—see—other solar systems for the first time. The Gemini Planet Imager (GPI) is an important scientific instrument being built by an international team led by Livermore astrophysicist Bruce Macintosh. Macintosh’s team was awarded the project in an NSF competition pitting the team against lower-cost proposals that failed to win the confidence of the sponsors. When completed, GPI will be the most capable adaptive optics system in the world. It will discover new solar systems, tell us what they’re made of, and provide insight into how our own system formed.