The 40th anniversary issue of Smithsonian magazine (August 2010) features asteroid-hunting astronomers Rik Hill and Ed Beshore of the UA's Mt Lemmon Observatory. The pair track near-Earth objects (NEOs) - asteroids and comets that come within 30 million miles of the Earth's orbit and have the potential to impact.
They are members of the Catalina Sky Search, which Smithsonian says "has found about 2,500 NEOs in the past decade—including 577 in 2009."