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In The Crosshairs

Arecibo Radio Observatory photograph

The Arecibo Radio Telescope near Arecibo, Puerto Rico, is composed of a dish with 40,000 aluminum panels, an overhead receiver and a system of wire trolleys. Incoming radio waves bounce off the dish and are captured by the receiver, which sends the data to scientists. The scope has appeared in movies including “Contact” and the James Bond film “GoldenEye.”

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By KURT LOFT, The Tampa Tribune

Published: December 24, 2007

TAMPA - They call them near-Earth objects, but they have another name: doomsday rocks.

They hide among the asteroids and comets that clutter our solar system, and as the sun's gravity pulls them close or Jupiter alters their path, they sweep past our planet. It's just a matter of time, astronomers say, before a big one hits home.

How will we know, and what will we do? These are questions that vex the science community and make fodder for Hollywood movies. But one thing is certain: Whether a piece of cosmic debris poses a threat depends on our ability to detect and track it early on.

Enter the Arecibo Radio Telescope.

This is the world's largest telescope dish, essentially a giant radar, located in the hilly jungles of Puerto Rico. Like a big eye, it scans the heavens for unusual signs - such as a doomsday rock.

But the observatory may soon go blind. Funding for its programs is being cut, and scientists fear they may lose 50 percent of Arecibo's $8 million budget by 2011, making it impractical to operate. That leads to a far greater problem, says Robert Kerr, the observatory's director.

"Arecibo is the only observatory in the world that can accurately predict whether the orbit of a near-Earth object will intersect Earth - and produce a catastrophe," he says. "We are also the only radio telescope that can image a near-Earth object. No other telescope could advise where or how to divert an incoming object destined to strike Earth."

Ordinary optical telescopes measure the position of an object in two dimensions - left to right and up and down. Arecibo does something more: It measures the object's distance and velocity from the Earth, and this gives scientists a better idea of where the object is going.

"If an asteroid happened to be heading nearly straight towards us, in an optical telescope it would appear not to be moving across the sky, and it would attract little attention," says Michael C. Nolan, head of Arecibo's radar astronomy group. "If you then measure it with radar, you would discover that it was getting closer and that you needed to pay attention."

Built in 1963 and measuring 1,000 feet across, Arecibo is the world's most sensitive radio observatory. It receives natural signals from galaxies as far away as 10 billion light-years and has been used to send out messages, with the faint hope they might be picked up by an intelligent civilization.

The observatory focuses on the radio portion of the electromagnetic spectrum (your typical backyard telescope focuses visible light). Incoming radio waves bounce off the dish's 40,000 aluminum panels and direct them to a receiver suspended 450 feet above the reflector dish. To adjust its line of sight, the receiver moves along a system of wire trolleys.

Although the observatory is 45 years old, periodic upgrades of instruments keep its cutting-edge resolution of objects in the sky, allowing it to detect objects the size of golf balls from 250,000 miles away. This year, more than 250 scientists around the world have booked observing time.

But the National Science Foundation, which funds Arecibo, wants to move money to other programs. If the foundation cuts continue - $2 million this year alone - the observatory will come close to shutting down in four years.

Such a fate, however, is hardly a done deal. Politicians from Puerto Rico and California have introduced legislation to save the telescope and emphasize its role in looking for potentially dangerous objects in the solar system.

"Nobel Prize-winning research has been conducted at Arecibo and may again in the future, unless the observatory is closed for short-sighted reasons," U.S. Rep. Luis Fortuno of Puerto Rico said in a statement. "The cost is small compared with the benefits for mankind."

Last month, a number of scientists addressed the issue of rogue asteroids and comets during testimony before the House Subcommittee on Space and Aeronautics. Donald Yeomans, a scientist with the National Aeronautics and Space Administration, stressed the importance of keeping Arecibo's big eye open to the sky.

"The planetary science community," he said, "is in danger of losing one of its instrumental crown jewels."

Reporter Kurt Loft can be reached at (813) 259-7570 or kloft@tampatrib.com.

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