”A hundred billion,” says Sigrid Close. That's how many meteors collide with the Earth's atmosphere every day. Most are whittled away in the ionosphere, and Close spends her days studying exactly how they disintegrate. That's right: she gets paid to watch shooting stars.
Close is the resident expert in ionospheric and near-Earth phenomena at Los Alamos National Laboratory in New Mexico. Her work regularly takes her to places like India, China, Puerto Rico, and the Marshall Islands, where she uses the most advanced space surveillance telescopes and radar to study the uppermost reaches of the atmosphere, some 85 kilometers above the Earth's surface.
Close's, and Los Alamos's, interest in shooting stars isn't purely academic. It turns out that meteors, as well as the ionosphere itself, disrupt radio signals. When meteors hit the atmosphere, they tend to melt into plasma plumes dense with heavy metals, sometimes causing big bubbles that momentarily block the path between a satellite and an Earth-based receiver. Similar disturbances, called equatorial plumes, occur naturally in the ionosphere, blossoming at sunrise and sunset, when the sun's radiation forces lighter plasma to well up as heavier plasma falls. For a satellite, Close says, the effect is as difficult to see through as ripples in a pond.
At Los Alamos's satellite operations center, Close works with a team of rocket scientists and engineers studying these plasmas to determine how and when they will cause problems. By better understanding the underlying physics, she says, aerospace engineers can better safeguard their systems. Her main responsibility is monitoring satellites for the U.S. Army's Air and Missile Defense Command, including one satellite that scans the skies for signs of clandestine nuclear tests. She also gets called in during satellite launches, which can be compromised by the meteor plasmas and the meteors themselves. ”You think you're tracking a launch,” Close explains, ”and actually the radar is just tracking these dense plasma structures.”
From an early age, Close says, ”I wanted to work on something in space.” As a child growing up in Allentown, Pa., she remembers her parents taking her out on clear nights ”to see Mr. Moon.” Her father, a computer engineer, gave her a telescope for her eighth birthday. In 1992, her love of space naturally led to a physics and astronomy B.S. at the University of Rochester in New York state.
Close then went to the University of Texas at Austin, intending to get a Ph.D. in physics. She finished her master's but went no further. ”I was burned out,” she says. It didn't help that a co-worker kept leaving Bible passages on her office chair exhorting women not to work. Close also wanted to spend more time on her music. Like her mother, she is a classically trained pianist. Close moved to Boston and recorded an album, Mirrored Self , released in 1997, an improbable blend of classical piano and postcollege angst.
Close took a job at MIT's Lincoln Laboratory to study the ionosphere. Her work involved heavy doses of engineering, especially signal processing. Learning to recognize the signature of a meteor or some other object on a radar screen, she says, is a lot like learning to read Braille. At first she had trouble distinguishing the White Sands missile range, in New Mexico, from an ocean or a forest. Over time, though, she became an expert in characterizing the noise that ionospheric and meteor plasmas can inject into signals.
In 1998, MIT sent her on a two-year stint to Kwajalein Missile Range, a tiny strip of land in the middle of the Pacific Ocean. There, she did space surveillance using the ARPA Long-Range Tracking and Instrumentation Radar, or as Close puts it, ”the big honking telescope.”
She soon found herself traveling to other telescopes all over the world, where she monitored satellite launches and the 8000 or so operational satellites circling the planet. ”Anytime anyone sent anything into space,” she says, ”we tracked it.” Fortunately, her husband, Greg, had the kind of job--he's a science-fiction and fantasy writer--that let him join her on her travels.
In 2000, she was accepted into the highly competitive MIT Lincoln Scholars Program, which allowed her to receive her full staff salary while she finished her physics Ph.D. For her doctorate, which she completed in 2004, Close figured out how to weigh meteors by their radar signatures, using data she'd collected at Kwajalein. ”If we know their weight,” she says, ”we know how much damage they can do.”
Pretty soon, Los Alamos came calling.
”I didn't even want to work here at first,” she says. Initial impressions can be intimidating. The national lab, best known as the home of the atomic bomb, sits on 162 square kilometers of desert in the middle of Bandelier National Monument. Striated cliffs tower above short, scrubby trees that dot the land like green sheep. The lab's wide border is flanked by a flimsy-looking chain-link fence. But closer to the main facility, menacing army-green vehicles patrol the grounds, aided by Terminator-like soldiers sporting camouflage and mirrored sunglasses, weighed down by guns so big they look fake.
Despite the lab's military trappings, Close says, ”I can't imagine leaving.” The atmosphere among the researchers and postdocs is congenial, relaxed, and prone to pranks, she says. Last year, an anonymous artist redrew the men's room stick-figure icon using Wite-Out to extend its round head into a cone. Later, during construction work on the ceilings, a rogue staffer marked dangerous areas with the exhortation to ”WATCH YOUR CONE.”
Beyond the silliness, the job lets Close deeply indulge her love of space. She's the proverbial kid in a candy store when she talks about her many ongoing projects. She admits that she has a tendency to take on too much. ”There's so much amazing stuff going on here,” she says, ”it makes it hard to choose.” In fact, she's already plotting her next project, funded by the Defense Advanced Research Projects Agency: taking on the troposphere.