AFRL research leads to bigger telescopes

Published Feb. 12, 2014
By Lee Ross
Nucleus editor

KIRTLAND AIR FORCE BASE, N.M. -- Any sufficiently advanced technology is indistinguishable from magic, wrote British author Arthur C. Clarke.

That quote could easily describe adaptive optics, technology that was pushed forward at Kirtland's Air Force Research Laboratory. And it's a technology that universities, private astronomers and others have "taken and run with," according to Robert Fugate, one of the principal drivers behind adaptive optics research at Kirtland.

In the introduction to the 2009 book "The Adaptive Optics Revolution," by Robert Duffner, a historian at Kirtland, Fugate described the technology as being akin to looking through frosted glass and seeing a clear image on the other side. That's essentially what adaptive optics do when it comes to looking through the atmosphere to see a clear image of a satellite or another object in space. He added that atmospheric distortion simply can't be overcome by building bigger and bigger telescopes.

"Eight, 10 and, soon-to-be 30 meter class telescopes certainly gather a lot of light, but because of the atmosphere, they only provide the same image detail as an 8-inch telescope in your backyard," he wrote. "Some astronomers feel that the development of adaptive optics is on a par with the invention of the telescope for producing new science about the universe, and ultimately about where humankind fits in the grand scheme."

The most recent and likely the most cutting-edge example of how adaptive optics have moved forward is the Giant Magellan Telescope, which is being built the desert of northern Chile. The telescope is expected to have a full complement of seven 8.4-meter mirrors by 2024. In 2020, with only four of those mirrors
in place, GMT will see "first light" from the dry, high desert of the Las Campanas Observatory high in the Andes mountains overlooking the Atacama Desert of Chile.

That telescope will also have the kind of adaptive optics developed for Kirtland's Starfire Optical Range, a 3.5-meter telescope that, in the early '90s, was the largest and most cutting-edge adaptive optics telescope anywhere.The SOR's adaptive optics system "reads" the atmosphere by shooting a laser beam and examining how the light bounces back and is reflected onto a sensor.

Using that information, the system makes tiny adjustments to its mirror to compensate for the way light is deformed by the atmosphere. The changes must be mind-bogglingly fast and precise; they are made by hundreds of actuators thousands of times per second, adjusting the mirror by up to eight microns each time. That's a fraction of the width of a human hair, which is about 100 microns in diameter. Because of the incredible science going on, SOR was also a great tool for recruitment after it was declassified in 1991, Fugate said.

"We had to beat people off with sticks," he said.

It made waves in the scientific community again when it was pointed at the bright star Kappa- Pegasus on Sept. 17, 1997, Duffner wrote in his book.

"Viewed without adaptive optics, Kappa-Pegasus appeared as a single blurred image," Duffner wrote.

When they turned on the adaptive optics system, Kappa-Pegasus was revealed to be two stars instead of just one.

"That discovery of a binary star promptly established the value of the 3.5-meter telescope's adaptive optics," Fugate wrote.

Fugate said one of the original applications for the technology for the Air Force was to develop directed energy, or laser, weapons that could be used from an airplane. There are also military applications in tracking satellites, or for "space situational awareness."

In addition to the military applications, it's a technological advance that could be used to discover life on other planets or unravel some of the mysteries of the creation of the universe. It has even been used to take detailed pictures of the inner workings of the human eye.

Fugate, who is a consultant working at Kirtland, said Starfire is still a great place for young researchers to get started.

"SOR is still one of the best places in the Air Force to get hands-on work," he said.