Can there ever be too many eyes watching the heavens?

It's been featured in movies such as Contact and Golden Eye and is visited by 90,000 people a year, including 200 scientists who get to use it for free.

But as far as monster telescopes go, the Arecibo Observatory in Puerto Rico could be heading for mothballs, clearing the way for China's FAST to assume the premiere role in listening for gravitational waves and keeping an eye on asteroids that may want to collide with Earth.

The future of one of the world's largest single-dish radio telescopes has come into question after the US National Science Foundation announced Wednesday that it was accepting proposals from anyone interested in taking over operation of the observatory.

The tender offer comes as the federal agency has run out of money to keep the 1,000-foot-wide dish in service.

In an interview with The Associated Press, foundation officials stressed that ideally the observatory would remain open with the help of collaborators that would provide a funding boost.

"Our (community reviews) have recognized that Arecibo does great science and will continue to do great science," said Ralph Gaume, acting director for the foundation's division of astronomical sciences.

However, he warned it was possible that none of the proposals that have to be submitted by late April will be chosen. This would leave the foundation with the options of suspending operations, turning it into an educational center or simply shutting it down, lights out.

The first hint that the 53-year-old observatory was at risk came a decade ago, when a panel of experts recommended it be shut down unless other institutions could help the foundation. The agency finances two-thirds of the observatory's $12 million annual budget, and officials said it could provide some $20 million over a five-year period to a potential new operator.

Scientists use the observatory in part to detect radio emissions emitted by objects including stars and galaxies, said observatory director Francisco Cordova.

However, he told the AP that could change depending on the type of proposals submitted.

"Perhaps in the future, scientists might have to pay to use it," he said, adding that the observatory still plays a key role in research including the study of solar eruptions capable of disrupting electronic equipment.

The observatory has been threatened in recent years by bigger, more powerful telescopes in places like Chile and China, where officials recently unveiled the mega-science Five-hundred-meter Aperture Spherical radio Telescope, or FAST, which claims top spot as the largest dish telescope in the world, a full 640 feet (or 64 percent) wider than Arecibo.

The $180 million FAST, which was funded by the National Development and Reform Commission and managed by the National Astronomical observatories of the Chinese Academy of Sciences (in cooperation with the government of Guizhou province), officially took its "first light", or went into service, last September.

Nicknamed "China's Eye on Heaven", FAST was first tasked with doing a survey of neutral hydrogen in space, observing pulsars and tracking spacecraft.

It will take three years to have the instruments fully calibrated and become fully operational, and as for serving as a tourist attraction, scientists worry about "noise" from nearby cellphone use, not to mention the difficulty in navigating the poor roadways to get there.

The dish sits in a natural sinkhole in southwest China's Guizhou province, from where a village of 65 people had to be relocated to make room for the monster.

The basic design of FAST is similar to Arecibo, both being fixed primary reflectors installed in natural geologic formations. Both are made of perforated aluminum panels with an adjustable receiver suspended above.

The big difference, aside from size, is that the FAST dish is significantly deeper, allowing a wider field of view.

Arecibo's big advantage is being closer to the equator, where it scans a wider swath of the sky.

The dream of science buffs, of course, is that both of these giant eyes work together, along with the other monster telescopes in place like Chile and Russia, so all of humanity gets a closer look at what's going on out there.

The National Science Foundation said it expects to make a decision on Arecibo by late 2017 as it awaits completion of a final environmental impact statement, which will outline all alternatives for the observatory's future. It will be interesting to see if President Trump's executive order on regulations has any impact.

Stay tuned.