Could robots help China save the world’s only giant radio telescope from collapse?

Robots will soon be deployed to carry out maintenance work at China’s giant radio telescope, state media reported, holding out hope for eliminating the potential hazards posed by human repair workers.

Located in China’s southern Guizhou province, FAST is the world’s largest single-dish radio telescope. It is now also the world’s only giant radio telescope, after the collapse of Puerto Rico’s Arecibo Observatory telescope in 2020.

The Arecibo collapse shocked many worldwide, but for those in charge of maintaining the 305-metre-wide (1,000 feet) instrument, alarming signs including poor maintenance had been present for almost two decades.

China’s FAST is only giant, single-dish radio telescope after Arecibo collapse

Maintaining a giant telescope can be as challenging as building it, with the huge number of cables, reflective panels and other mechanical components needing to be regularly checked for wear or cracks.

Fears that the FAST telescope might suffer the same fate as Arecibo have long troubled astronomical societies world wide. China hopes that the robots will make a difference.

According to the official Arecibo collapse report, it was observed in 2003 that the cables holding up the 900-tonne feed structure – housing the telescope’s radio wave receiver – had started to slip out of their sockets.

This was not addressed in time, and only fully investigated after the feed structure collapsed.

The FAST telescope is almost 200 metres wider than Arecibo was, and its feed cabin is also 30 times lighter at only 30 tonnes.

According to the Chinese Academy of Sciences (CAS), the country’s largest scientific body, the lightweight design was a deliberate move, aimed at avoiding the “rigid-structure design” of the feed support like that of Arecibo.

A member of staff walks under the feed cabin of FAST in China’s Guizhou province. Photo: Xinhua

There are still major challenges to maintaining a giant telescope. Maintenance workers face difficulties accessing parts due to their size or design, and could themselves cause harm to the structure, FAST engineers told Xinhua.

The five intelligent robots, designed by Chinese institutes, were created specifically to address likely maintenance issues with FAST, the report said.

The smart robots will be able to clean and maintain the telescope’s spherical dish – made up of laser targets underneath reflective aluminium plates. They will also be able to travel along the cables supporting the feed cabin to scan for defects, and assemble and disassemble the receiver from the cabin.

FAST’s receiving dish is made up of thousands of laser targets and millimetre-thin reflector plates, which cannot withstand human weight. Workers have to be partially suspended by a balloon in order to avoid damaging the plates, Tao Rui, a designer of the maintenance robocar, told Xinhua.

According to the CAS’s Institute of Automation, the robocar designed for the dish is able to travel on inclines, at angles of up to 56 degrees, to clean and maintain the rounded structure.

Tao said the weight distribution of the dish maintenance robot or robocar allowed it to traverse the plates without causing damage to the reflectors and targets, which are the most important part of controlling FAST and thus require regular maintenance.

Another of the five robots has been designed to monitor the large cables that hold and position the feed cabin. Sui, a researcher at the Harbin Institute of Technology, said the robot was capable of travelling along the cables and uses a magnetic detection sensor to search for internal defects.

A 280-metre section of the cable is inaccessible to human workers, so the robot was designed to ensure engineers could monitor the entire length, Sui told Xinhua. His team also designed a control system to drive the robots along the cables and allow for more “stable detection”.

The engineering firm that prepared the collapse report found that persistent failure of the support cables and connection sockets triggered the collapse of the Arecibo feed structure, which was “highly stressed under its own weight”.

The damage at the Arecibo Observatory after one of the main cables holding the receiver broke in December 2020. Photo: AFP

The US National Science Foundation, which owned Arecibo, told the Post by email that a variety of factors contributed to the collapse, including “unique environmental conditions” and socket manufacturing defects.

The NSF “cannot speculate if robotic devices travelling along the cables may have provided any useful information”, as the forensic study showed that the most critical activity that contributed to the collapse was hidden in the sockets, a spokesperson said.

“[Diagnosing these issues] would have required X-ray imaging or may have been inferred from more careful monitoring of the slippage.”

Inside China Tech: ‘Sky Eye’ stays focused on space after Arecibo collapse

The differences in FAST’s feed structure compared with Arecibo were designed by CAS to avoid the issues the Puerto Rican telescope faced, and could prevent a similar collapse under its own weight. Also, according to the Chinese authorities, the use of robot repair workers could mean issues are diagnosed much earlier.

Chang, an engineer on the FAST project, said the development of the robots “solves the problem of high cost, low efficiency” by automating tasks and reducing maintenance downtime, the Xinhua report said.

Jiang Peng, chief engineer at FAST, told state-run CGTN earlier this month that the reduced maintenance time from operating the intelligent robots could add 30 days to the annual observation period of the telescope.

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