From BBC News, 2011, Adaptive optics come into focus:
Back in 1953, Horace Babcock had an idea. As an astronomer, he was toiling with the problems caused by the Earth's atmosphere.
Light could come from the farthest reaches of the cosmos, billions of light years, and then get impossibly muddled up in the last couple of hundred kilometres as it passed through the turbulent gases that envelop the Earth. So he came up with the idea of adaptive optics: figuring out just how the atmosphere muddled up the light, and subtly changing the shapes of optical elements like mirrors to perfectly undo those effects.
It took the US defense industry - and a purported $1bn - to put the idea into practice in the 1970s and 1980s. They were trying to get ever-better satellite pictures - sort of the astronomer's problem in reverse.
Applying adaptive optics to telescopes and astronomy required a number of advances in laser technology, computing power, and and the construction of telescope mirrors and other optics in order to gather atmospheric data, process the data to determine the corrective response, and submitting the response to the telescope to modify the optics...all continuously, in real-time.
The Keck 10-meter telescope in Hawaii began using its adaptive optics system in 2001 -
Keck Uses Adaptive Optics for the First Time:
In January 2001, after more than seven years in development, the Keck and LLNL teams celebrated the completion of the Keck laser guide star system. The artificial star results when light from a 15-watt dye laser causes a naturally occurring layer of sodium atoms to glow about 90 km (56 miles) above the earth’s surface. It would take another two years of sophisticated research and design before the laser system could be integrated into the Keck II adaptive optics system.
In the early morning hours of September 20th, all subsystems finally came together to reveal the unique capability of the Keck LGS AO system and its potential to resolve extremely faint objects. The system locked on a 15th magnitude star, a member of a well-known T Tauri binary called HK Tau and revealed details of the circumstellar disk of the companion star. It was the first time an adaptive optics system on a very large telescope had ever used an artificial guide star to resolve a faint object.
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The quality of the LGS AO first light images was extremely high. While locked on a 14th magnitude star, the Keck LGS AO system recorded “Strehl ratios” of 36 percent (at 2.1 micron wavelength, 30-second exposure time, Figure 3), compared to four percent for uncorrected images. Strehl ratios measure the degree to which an optical system approaches “diffraction-limited” perfection, or the theoretical performance limit, of the telescope.
Another performance metric, the “full width at half maximum” (FWHM), for this 14th magnitude star was 50 milli-arcseconds, compared to 183 milli-arcseconds for the uncorrected image. FWHM measurements help astronomers determine the actual edges of an object, where the detection may be imprecise or difficult to determine. The measurement of 50 milli-arcseconds is about equivalent to being able to distinguish a pair of car headlights in New York while standing in Los Angeles.
The new adaptive optics system at Gemini South continues the advancement of technology to improve the our giant earthbound 'eyes'.
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