ARECIBO, PUERTO RICO — In its 45 years, the Arecibo Observatory has amassed an impressive list of accomplishments. It took some of the first pictures of Earth's changing surface signaling global warming and has mapped the surface of Mars with more precision than any other instrument.

It also houses the only radio telescope in the world that can predict with enough accuracy just where and when an asteroid would hit Earth.

Yet the Cornell University-run observatory is struggling to stay open after the National Science Foundation, its main funding source, decided last year to slash its budget to $8 million from $10.5 million. By 2011, the money is expected to dwindle to $4 million.

The foundation cuts also came with a warning: Find other funding sources or risk getting shut down.

The Arecibo observatory, near the island's northwestern coast, is considered by many to be one of the world's top engineering marvels. Its 1,000-foot-diameter dish — the size of 26 football fields — is the biggest in the world. It is also the most powerful, with the capability to probe objects 10 billion light-years away.

The gigantic dish is suspended above a natural sinkhole surrounded by limestone hills and a thick forest. It hangs from steel wires strung on 300-foot pillars that, guided by laser beams, adjust to radio frequencies.

It was a hard decision

Hundreds of scientists from all over the world come to this remote rural post for the chance to work with this one-of-a-kind instrument. Closing the facility would be "lunacy," Arecibo Director Robert Kerr said.

"There are obvious benefits to humankind that come out of this place which can't be duplicated elsewhere," he said.

The science-foundation cuts were based on budget forecasts that assumed the agency's funding would remain flat for the next five years. Because the agency gets so many recommendations each year for new scientific endeavors, foundation officials said they had to set priorities and make hard choices.

"We had to look at everything that we were doing in a uniform way and see how we could proceed to free some money to do some new things," said Wayne Van Citters, division director for astronomical science at the foundation.

But critics point out that the foundation's financial outlook has since changed for the better. Under President Bush's American Competitiveness Initiative, which commits $50 billion for scientific research during 10 years, the agency's budget has been growing steadily. Nevertheless, funding for Arecibo has not been restored.

Not enough to go around

Van Citters said the science foundation's senior review board had considered potential budget increases for the agency when issuing its recommendations.

"Even if our budget was to double, there simply wouldn't be enough money to do everything everybody wants," Van Citters said.

Foundation officials also maintain that NASA should fund Arecibo because it greatly benefits from the observatory's findings.

Kerr says the agency is passing the buck.

"The NSF now says NASA should be the one that pays for it. NASA says it should be the NSF. It is insane political football," Kerr said.

Scientists have come out in support for restoring funding to Arecibo. Last year dozens of astronomers appeared at a hearing before Congress to ask that the facility be saved from the budget ax.

But nothing gets done without political muscle.

The commonwealth does not have a congressional delegation in proportion to its 4 million residents. It is represented in Congress by a nonvoting House member.

"It is easy to run over Puerto Ricans," Kerr said. "We have, by structure, very poor representation in Washington."

By contrast, other facilities that were also placed on the science foundation's chopping block have since secured funding after a powerful politician came to their rescue.

Seeking a champion

New Mexico Sen. Pete Domenici, a Republican member of the Senate's appropriations subcommittee, which funds the science foundation, fired off a letter to the agency in October blasting it for cuts that would have forced the National Radio Astronomy Observatory to shut down. The national group runs six observatories, two of them in New Mexico.

Afterward, Domenici met with foundation Director Arden Bement. As a result, the national observatory group was able to maintain nearly the same budget level for 2008 — $44.52 million — and stands to get another $18 million in 2009.

Arecibo has not been as lucky. A bill that seeks to secure funding for it was filed in October by Republican Luis Fortuno, the island's nonvoting representative, but has received little attention.

A spokesman for Fortuno said the congressman thinks Arecibo should be saved based on the facility's uniqueness.

It remains to be seen whether Congress can be persuaded. For the science foundation, this makes little difference. Van Citters explained that, like Arecibo, all the other facilities recommended for shutdown were doing unique science.

"Their work has not been duplicated elsewhere," Van Citters said. "But if you look at our entire science program, we can only fund between 25 percent and 30 percent of the projects that are recommended."

There appears to be no immediate solution on the horizon, but Kerr is optimistic.

"This place is not going anywhere, in spite of politics," Kerr said. "We won't stop until we make sure of that."