Requiem for a telescope
By Dennis Overbye
When the giant Arecibo Observatory in Puerto Rico collapsed in December 2020, it punched a hole in astronomy.
For half a century Arecibo was the mightiest telescope on the planet. One thousand feet wide, it listened to radio signals from the stars — as well as from pulsars, planets, asteroids and more — for any hints of intelligent life, potentially Earth-killing objects, and insights into the mysteries of gravity and space-time.
The demise of Arecibo also punched a hole in the pride and the economy of Puerto Rico, which has repeatedly been hit by hurricanes, earthquakes and widespread electrical outages. Since 1963, when the telescope was founded, generations of schoolchildren in the territory have trooped through the hills to a sci-fi setting: a gigantic, concave antenna, set like a mixing bowl in a mountain valley, with 900 tons of radio receivers suspended above it. There, young students could rub elbows with renowned scientists at work and be inspired by science, particularly astronomy. Many grew up to be astronomers themselves.
Those trips will continue, sort of. Last week the National Science Foundation, which owns the Arecibo Observatory, said it would spend $5 million to establish a world-class educational center at the site. The Arecibo Center for STEM Education and Research would include the Ángel Ramos Science and Visitor Center, as well as an exhibition space, a laboratory, office space, dormitories, an auditorium and a cafeteria.
The only thing missing will be the telescope. The plan “does not include rebuilding the 305-meter telescope or operational support for current scientific infrastructure, such as the 12-meter radio telescope or Lidar facility,” the National Science Foundation said last week in a statement soliciting proposals from researchers hoping to conduct projects at the site.
Dan Werthimer, an astronomer at the University of California, Berkeley, who had used the telescope throughout his career to search for radio signals from extraterrestrial civilizations, lamented the decision to not rebuild. “Arecibo was my favorite telescope in the universe,” he said.
“This is a sad time for the people of Puerto Rico, ”Werthimer added. “The Arecibo telescope was their pride and joy.”
The sense of loss rippled through the astronomical community.
“It was then a great surprise last Thursday when the NSF announced that it planned to turn the facility into a mainly STEM education side and curtail almost all of the science,” Joanna Rankin, a radio astronomer from the University of Vermont and part of a group of some 400 astronomers known as the Arecibo Science Advocacy Partnership, wrote in an email. “Many of us who have used the instrument and know its many virtues have been quite disconcerted by this unexpected turn of events.”
A headline in The Register, a daily online journal covering technology, complained that the NSF planned to replace the telescope with a school.
The Arecibo Observatory, officially named the National Astronomy and Ionosphere Center, was originally built as an interplanetary radar as well as a radio telescope to study, among other things, the properties of objects such as warheads tumbling through the atmosphere. Over the years it stood as a symbol of human curiosity and cosmic optimism. It appeared in the film “Contact,” which features Jodie Foster as an astronomer who discovers a communication signal from outer space, and in “Goldeneye,” as the lair of wa James Bond supervillain.
The telescope helped radio astronomers win a Nobel Prize in physics for their observations of a pair of pulsars emitting gravitational waves, the ripples in space-time that had been predicted by Albert Einstein. It also joined a new planetary defense initiative by NASA, tracking and bouncing radar off potential killer asteroids.
But time, diminishing budgets and insufficient maintenance took their toll.
In November 2020, a cable holding the 900-ton platform of radio receivers in the air over the dish snapped, leaving the instruments dangling perilously. The NSF began making plans to take the telescope down, but nature beat them to it. On the morning of Dec. 1, 2020, the remaining cables snapped, and the platform came crashing down, demolishing the dish and everything around it.
Astronomers were heartbroken. But science is nothing if not resilient. Before the final collapse occurred, scientists rallied together to figure out how to rebuild or replace the beloved telescope.
Their efforts culminated in a paper describing what its 70-odd authors called the Next Generation Arecibo Telescope, or NGAT. The paper was submitted to the National Academy of Sciences as part of a survey of astronomical priorities for the next decade.
China has recently built an even bigger radio telescope, the Five-hundred-meter Aperture Spherical Telescope, or FAST, but giant dishes have mostly gone out of fashion in radio astronomy, in favor of arrays of much smaller dishes that can collect the same amount of radio energy but in a more versatile manner. The NGAT team envisioned 1,112 antennas, each 30 feet wide, on a giant movable platform or collection of platforms that could tilt or swivel to point in many more directions in the sky than the original Arecibo antenna, which was fixed to the ground and limited in how far from the celestial zenith it could point.
The NGAT proposal came with a list of subjects that could potentially be studied if the telescope were rebuilt: pulsars circling the supermassive black hole at the heart of the Milky Way; molecules in the early universe; space debris and space weather; dark energy and dark matter; and much more.
“These capabilities will vastly increase the user base of the facility and enable cutting-edge science for decades to come,” the authors, led by Anish Roshi, a senior scientist at the Arecibo Observatory, wrote in their proposal.
Radio astronomers concede that, in the best of all possible worlds, the optimal site for a telescope like the one proposed by the NGAT team would be high and dry, in a desert, rather than in the stormy and humid mountains of Puerto Rico. But the moral debt to Puerto Rico reigns supreme.
The proposal came with a price tag of $454 million, a hefty load for the NSF, which is also fielding requests to invest billions in gravitational wave detectors, a pair of giant optical ground-based telescopes and other ambitious projects that would help American researchers keep pace with the rest of the world.
In remarks to The Associated Press, an NSF official said the government already had other instruments that could fulfill some of the duties of the old telescope.
In an email, Roshi said that astronomers loved the idea of a center for science, technology, engineering and math at Arecibo, but he questioned whether it made sense to establish one there without an accompanying research facility.
“In my opinion, the observatory and the larger scientific community should use this opportunity to strengthen the effort to rebuild the telescope and avoid destroying the observatory and other research activities currently underway at Arecibo,” Roshi said.