BYE BYE SO LONG
Big dish of Arecibo observatory has reached the end of the line
With no way to safely repair it, the National Science Foundation calls it.
JOHN TIMMER - 11/19/2020 ARS TECHNICA
Enlarge / An aerial view of the Arecibo facility, showing the increasingly fragile cables supporting the instrument platform, as well as the gash caused when one of those cables failed.
Today, the National Science Foundation announced that its famed Arecibo radio observatory would be shut down. Built into a hilltop in Puerto Rico, the main dish of the observatory is over 300 meters across, and its massive size has made it a feature in popular culture ranging from James Bond movies to video games. But despite a long history of scientific contributions, the observatory has been struggling for funding for over a decade, and two cables that support it have failed this year, leaving it in a precarious state.
After engineering studies determined there was no way to repair the hardware without putting workers at risk, the NSF made the decision to shut the observatory down.
More than a big dish
While the sheer scale of the main dish at Arecibo grabbed the most attention, the dish was purely a reflector. The actual business end of the telescope, where radio waves were sensed, was an instrument platform suspended high above it by cables strung from three towers. The instrument platform held a receiver that could be moved to different locations above the disk, giving it the ability to resolve signals from more directions than its fixed dish might suggest.
Since its commissioning in the 1960s, the observatory has played a role in many discoveries, primarily in the field of pulsars, a class of radio-emitting neutron stars. It has also been involved with SETI searches, and it transmitted an image to a star cluster under the assumption that any intelligent life there might be partaking in its own SETI program. But over the last 15 years or so the NSF, Arecibo's primary means of support, has cut its funding for the observatory, which has struggled to maintain full operations over this period.
But it wasn't money that eventually doomed Arecibo; instead, it was the instrument platform. In August of this year, one of the auxiliary cables that help support the platform snapped, creating a gash in the radio-reflective dish below. While plans were being made to replace that cable and repair the dish—replacement cables were already on order—one of the 7.5cm main cables on the same tower snapped on November 6
An engineering analysis subsequently determined that this cable failure happened despite the fact that the strain on it was only about 60 percent of what should be its minimum breaking strength. This raised serious questions about the stability of the remaining cables, and thus the ability of the structure to support its instrument platform. The analysis concluded that it was unsafe to find out; the platform could collapse without warning, and any snapped cables would present a danger to any workers on the towers, as the large cables would move at very high speeds following a break. Of the three additional engineering firms consulted by NSF and the University of Central Florida, two agreed with this assessment.
"Until these assessments came in, our question was not if the observatory should be repaired but how," said the NSF's Ralph Gaume. "But in the end, a preponderance of data showed that we simply could not do this safely. And that is a line we cannot cross."
The end is near
Right now, the NSF is simply announcing that it will start planning for the decommissioning process. Work was already underway to move the data archives from the instrument onto a cloud service, and the plans for safely removing the platform will obviously involve a lot of additional engineering analyses. The NSF said that several other scientific programs associated with the site will remain open. The observatory also serves as a major focus of outreach between the scientific community and Puerto Rican society—understanding how to maintain that dynamic in the absence of an active instrument will also require further study.
It's difficult to argue with the risk analysis. And it's not difficult to imagine that more modern and flexible instruments can accomplish the science we'd expect from Arecibo at a lower cost, which explains why Arecibo has been struggling for funding for over a decade. Given both of these factors, it's clear that Arecibo's time has come.
But it's still difficult to accept the loss of an icon like this.
With no way to safely repair it, the National Science Foundation calls it.
JOHN TIMMER - 11/19/2020 ARS TECHNICA
Enlarge / An aerial view of the Arecibo facility, showing the increasingly fragile cables supporting the instrument platform, as well as the gash caused when one of those cables failed.
After engineering studies determined there was no way to repair the hardware without putting workers at risk, the NSF made the decision to shut the observatory down.
More than a big dish
While the sheer scale of the main dish at Arecibo grabbed the most attention, the dish was purely a reflector. The actual business end of the telescope, where radio waves were sensed, was an instrument platform suspended high above it by cables strung from three towers. The instrument platform held a receiver that could be moved to different locations above the disk, giving it the ability to resolve signals from more directions than its fixed dish might suggest.
Since its commissioning in the 1960s, the observatory has played a role in many discoveries, primarily in the field of pulsars, a class of radio-emitting neutron stars. It has also been involved with SETI searches, and it transmitted an image to a star cluster under the assumption that any intelligent life there might be partaking in its own SETI program. But over the last 15 years or so the NSF, Arecibo's primary means of support, has cut its funding for the observatory, which has struggled to maintain full operations over this period.
But it wasn't money that eventually doomed Arecibo; instead, it was the instrument platform. In August of this year, one of the auxiliary cables that help support the platform snapped, creating a gash in the radio-reflective dish below. While plans were being made to replace that cable and repair the dish—replacement cables were already on order—one of the 7.5cm main cables on the same tower snapped on November 6
An engineering analysis subsequently determined that this cable failure happened despite the fact that the strain on it was only about 60 percent of what should be its minimum breaking strength. This raised serious questions about the stability of the remaining cables, and thus the ability of the structure to support its instrument platform. The analysis concluded that it was unsafe to find out; the platform could collapse without warning, and any snapped cables would present a danger to any workers on the towers, as the large cables would move at very high speeds following a break. Of the three additional engineering firms consulted by NSF and the University of Central Florida, two agreed with this assessment.
"Until these assessments came in, our question was not if the observatory should be repaired but how," said the NSF's Ralph Gaume. "But in the end, a preponderance of data showed that we simply could not do this safely. And that is a line we cannot cross."
The end is near
Right now, the NSF is simply announcing that it will start planning for the decommissioning process. Work was already underway to move the data archives from the instrument onto a cloud service, and the plans for safely removing the platform will obviously involve a lot of additional engineering analyses. The NSF said that several other scientific programs associated with the site will remain open. The observatory also serves as a major focus of outreach between the scientific community and Puerto Rican society—understanding how to maintain that dynamic in the absence of an active instrument will also require further study.
It's difficult to argue with the risk analysis. And it's not difficult to imagine that more modern and flexible instruments can accomplish the science we'd expect from Arecibo at a lower cost, which explains why Arecibo has been struggling for funding for over a decade. Given both of these factors, it's clear that Arecibo's time has come.
But it's still difficult to accept the loss of an icon like this.
Adiós Arecibo Observatory: America's largest radio telescope faces explosive end after over 50 years of service
The aging structure is too hazardous to repair, engineers say
The Arecibo Observatory, America’s largest radio telescope, is to be blown up after the National Science Foundation decided recent damage has left it too dangerous to repair.
“NSF prioritizes the safety of workers, Arecibo Observatory’s staff and visitors, which makes this decision necessary, although unfortunate," its director, Sethuraman Panchanathan, said in a statement on Thursday.
"For nearly six decades, the Arecibo Observatory has served as a beacon for breakthrough science and what a partnership with a community can look like. While this is a profound change, we will be looking for ways to assist the scientific community and maintain that strong relationship with the people of Puerto Rico."
In 2017 the telescope was severely damaged by Hurricane Maria but things got worse in August when a three-inch auxiliary cable, supporting a 900-ton platform above the telescope's dish, popped out of its socket and came falling down, tearing a 100-foot hole in its metal panels.
The remaining cables struggled to withstand the added strain, and disaster struck again in November after a main cable broke and damaged the dish further. Officials at the University of Central Florida (UCF), who managed the observatory in Puerto Rico, warned it was a race against time to repair the fraying structure.
All efforts to fix the issues, however, have now been abandoned. Thornton Tomasetti, one of the engineering firms hired to investigate the mishap, warned that if another main cable were to fall a catastrophic failure would be very likely.
“While this outcome is not what we had been working towards, and we are disheartened to see such an important scientific resource decommissioned, safety is our top priority," the firm said in a letter addressed to UCF and reviewed by The Register.
Now, the NSF will plan to carry out “controlled demolition” of the 305-meter telescope, following Thornton Tomasetti’s advice. “Although it saddens us to make this recommendation, we believe the structure should be demolished in a controlled way as soon as pragmatically possible," the firm said
"It is therefore our recommendation to expeditiously plan for decommissioning of the observatory and execute a controlled demolition of the telescope."
Other parts of the observatory, however, like its LIDAR facility, focused on geospace research, and its visitor center and offsite Culebra facility that monitors Earth’s climate, will reopen after the telescope is decommissioned. Initially, UCF asked for extra funding from the NSF to repair the observatory and launched a formal investigation into what caused the incident.
"Leadership at Arecibo Observatory and UCF did a commendable job addressing this situation, acting quickly and pursuing every possible option to save this incredible instrument," said Ralph Gaume, director of NSF's Division of Astronomical Sciences.
"Until these assessments came in, our question was not if the observatory should be repaired but how. But in the end, a preponderance of data showed that we simply could not do this safely. And that is a line we cannot cross."
Scientists say their goodbyes to the plucky radio telescope
The striking structure has stood in the middle of a national forest in Puerto Rico for over half a century. The telescope paved the way for astronomers to discover the first binary pulsar star and exoplanet, and to analyze numerous potentially hazardous asteroids. It even helped locate the SOHO solar spacecraft, jointly operated by NASA and ESA, when it lost communication with ground control after its gyroscopes failed.
“I have extremely fond memories when I think back to 1998 and how helpful and supportive Donald Campell - who was Director [of the observatory] at that time - and all of the staff at Arecibo were,” Bernhard Fleck, a Project Scientist for the SOHO mission, told El Reg.
“I had contacted Dr Campell late Friday afternoon on July 17, 1998. Two days later on Sunday, 19 July, he was on a plane down to Puerto Rico to oversee these unique radar measurements of a lost spacecraft over 1.5 million kilometers away, I believe a first in space history.”
“The successful detection of SOHO by Arecibo Radar was the turning point in the SOHO recovery and an incredible boost to the morale of the recovery team. Arecibo Radar confirmed that SOHO was still at its predicted location and was not spinning excessively fast.”
Although the loss of America’s largest radio telescope will mean there will be no new observations at the facility, there is still plenty of backlogged data remaining to be analyzed.
“At a time when public interest and scientific curiosity about space and the skies has re-intensified, there remains much to understand about the data that has been acquired by Arecibo,” a UCF’s President Alexander Cartwright told The Register. “Despite this disappointing setback, we remain committed to the scientific mission in Arecibo and to the local community.”
“Critical work remains to be done in the area of atmospheric sciences, planetary sciences, radio astronomy and radar astronomy. UCF stands ready to utilize its experience with the observatory to join other stakeholders in pursuing the kind of commitment and funding needed to continue and build on Arecibo’s contributions to science.” ®
