NSF’s Arecibo strategy puts future research into question

Two years ago, the 305-meter radio telescope at Arecibo Observatory in Puerto Rico collapsed because of cable failures. After an emergency cleanup and an investigation of the accident, NSF, which owns the site and operates it via a cooperative agreement with the University of Central Florida, announced on 13 October that it is seeking proposals through February to transform the observatory into an education center. The decision left many astronomers disappointed but not surprised, and it leaves the future of astronomy research at the site uncertain.

Completed in 1963, the iconic telescope at Arecibo was designed to detect trails left by enemy missiles traveling through the ionosphere. It subsequently served the science community as the premier instrument for observing pulsars. The telescope was used to determine the rotation rate of Mercury, make the first radar observation of a comet, find the first observational evidence for gravitational waves, and identify the first extrasolar planets. The telescope was also critical to NASA, especially the agency’s efforts to characterize near-Earth objects (NEOs).

The observatory was a source of pride and economic value to Puerto Ricans. School-age children would visit the observatory every year, and the visitor center attracted some 100 000 people annually before the collapse. (For more on Arecibo’s legacy, see the article by Daniel Altschuler, Physics Today, November 2013, page 43 .)

Reaction to the decision

The goals of the future Arecibo Center for STEM Education and Research will be to implement a research and workforce development program, host STEM education and outreach activities, support the participation of underrepresented groups in science, and build partnerships with the community in Puerto Rico and more broadly. The specifics of what the center will offer and how those offerings will be implemented depend on the institution (or consortium of institutions) with the winning proposal.

Debra Fischer, director of NSF’s Division of Astronomical Sciences, says that not repairing the radio telescope “was a really tough decision, and there was a lot of discussion inside NSF and with the community.” She says that the agency followed the guidance of the research community from two reports published by the National Academies of Sciences, Engineering, and Medicine: Pathways to Discovery in Astronomy and Astrophysics for the 2020s, which is commonly known as Astro2020 , and Origins, Worlds, and Life: A Decadal Strategy for Planetary Science and Astrobiology 2023–2032.

The steering committee of the Astro2020 survey wrote in chapter 5 that “much of what was lost with Arecibo can be replaced.” In an appendix to the report, however, the specialized Panel on Radio, Millimeter, and Submillimeter Observations from the Ground said that “the loss of Arecibo’s capabilities will significantly impact the ability of the U.S. astronomy community to address high-priority Astro2020 science questions.”

Héctor Arce is a professor of astronomy at Yale University and the outgoing chair of the board for the Arecibo Science Advocacy Partnership (ASAP), which has been advocating for NSF to repair or upgrade the observatory. Of the Astro2020 survey, Arce says, “I would not refer to a decision that was made by a nonelected committee of 20 people, where only one was a radio astronomer, as one that was reached through community input.”

Arce, who was born and grew up in Puerto Rico, has visited Arecibo many times over his more than two-decade career. Like other researchers, he brought his students to use the telescope and learn from the radio-astronomy community there. “One thing that has taken place there for a long time has been the research experience for undergraduates,” he says. “There have been teacher trainings and activities and research experiences for high schoolers as well as university students.”

NSF plans to fund Arecibo’s transformation with $5 million to be awarded over five years. Under its current arrangement with the University of Central Florida–led consortium, the agency has contributed $7.5 million per year (see “NSF puts Arecibo Observatory on chopping block,” Physics Today online, 24 November 2020 ). Anne Virkki, a planetary scientist at the University of Helsinki and the current board chair at ASAP, says “it’s not about them [NSF] wanting to close Arecibo. To me, it seems that they just want to use as little money on it as possible.”

Research continues after the collapse

Even after the telescope’s collapse, research and education—partly through undergraduate student projects—has continued at Arecibo. The observatory still has various instruments, including a 12-meter radio telescope, a radio spectrometer system called Callisto, and two lidar facilities. Data from the 12-meter telescope and Callisto have been particularly useful for solar and space-weather researchers studying the initial stage of solar eruptions, for example, and for predicting flares and coronal mass ejections.

A new cooling system being planned for the 12-meter telescope, which currently operates at 2.21–2.34 GHz and 8.1–9.2 GHz, will enhance the telescope’s sensitivity and broaden its frequency coverage to 2.3–14 GHz. Periasamy Manoharan—the principal investigator for the 12-meter telescope and Callisto—says that when the upgrade is ready, by early next year, the telescope will be able to observe compact background radio sources and probe the ambient solar wind and three-dimensional structures of the inner heliosphere.

The lidar instruments, one at Arecibo and the other on the neighboring island of Culebra, measure aerosols and collect optical measurements of the upper atmosphere in a region that’s too high for aircraft and experimental balloons but too low for satellites.

According to an NSF spokesperson, Arecibo’s research facilities currently in operation will remain open until at least March 2023, when the agreement with the University of Central Florida ends. After that, the institution awarded the funding for the research and education center will review project proposals and decide whether to maintain existing research facilities.

The Arecibo telescope’s primary contribution to astrophysics is the discovery of new pulsars and their timing. The Astro2020 report, therefore, recommended that the site’s lost capabilities be replaced by devoting more resources for pulsar timing to the Jansky Very Large Array in New Mexico and the Green Bank Telescope (GBT) in West Virginia and by collaborating with the international pulsar community.

The planetary decadal survey published in April 2022 states that Arecibo has been “a vital asset for radar observations” and that “Arecibo’s loss has drastically reduced the capability for follow-up radar characterization of NEOs.”

Other observatories can perform only a fraction of the functions of the now inoperable 305-meter dish. The 70-meter antenna at the Goldstone Deep Space Communications Complex in the Mojave Desert of California is usually used for spacecraft communications but has been used as a radar antenna to image planets, comets, and asteroids.

The GBT was built for radio-astronomy research, and China’s Five-Hundred-Meter Aperture Spherical Radio Telescope (FAST) has a design and use similar to Arecibo’s. For the first year of normal operation of FAST in 2021, only 10% of the observation time was allocated to scientists based outside of China.