Shanghai's giant radio telescope could be a white elephant
Scientists fear that the city's huge radio telescope may pick up more mobile phone conversations than any signals from outer space
Shanghai, you may have a problem. Municipal government officials have just attended a ceremony to mark the completion of a "landmark" radio telescope in the city.
The dish, with a diameter of 65 metres and weighing 2,700 tonnes, is the biggest, costliest and most technically advanced radio telescope ever built in China.
It's something that no other major city has - or would even contemplate having - and there's a good reason for that.
Many astronomers have questioned the project since its inception in 2008 because radio telescopes are designed to pick up extremely faint radio waves from celestial bodies such as stars and galaxies that could be more than 12 billion light years away.
Big cities such as Shanghai, which generate lots of radio noise from such things as cell phones, police radios and air traffic control are regarded as the worst possible place to put up a dish.
Nearly all of the world's largest radio telescope projects have been built in remote areas, far from human activity, with some even set atop high mountains to ward off unwanted interference. America's Very Large Array, for example, was built in New Mexico, 80 kilometres from the nearest city, which has a population of just 9,000.
Dr Shen Zhiqiang, the Shanghai 65M Radio Telescope's chief scientist, said he was a bit fed up after being quizzed by so many people about its location. He's reduced his defence to one sentence.
"It is no longer possible to find a site on earth where you can avoid man-made signals," he said.
Seven years ago Shen, a researcher with the Chinese Academy of Sciences' Shanghai Astronomical Observatory, was a rising star in Chinese astronomy. In 2005, an international team he led made a big splash in astronomical circles when it found solid evidence of the existence of a super-massive black hole at the centre of the Milky Way.
Some astronomers now worry that Shen's controversial radio telescope could be another black hole.
The telescope is designed to listen to cosmic radio waves with a frequency of 1.8 GHz or above. But the GSM networks of Chinese mobile phone service providers such as China Mobile run at 1.8 GHz and their 3G networks at 2.0 GHz. In other words, a special celestial event could be lost in the noise of a thousand phone calls.
To avoid that embarrassment, Shen said it would turn its ears to high-frequency signals, way above 2.0GHz.
"We are not interested in low-frequency events, anyway," he said.
Some mainland astronomers, who declined to be named due to the sensitivity of the issue, said politicians in Shanghai had silenced criticism with influence and money. In June 2008, some astronomers were summoned to Shanghai to review the project's proposal. No one raised any objections, according to a document on the project's website.
"Even a high school student with basic knowledge about radio astronomy would have raised doubts and objections to the location," one Beijing-based astronomer said. "The unanimous agreement could be the result of a bribe or political pressure, if not both."
Dr Wen Zhonglue, a researcher with the National Astronomical Observatories, said some leading astronomers had expressed doubts about the project because of the noise issue.
"Frequency range is a key benchmark of a telescope's performance," he said. "If signals with 2.0 GHz or lower have to be thrown into the waste bin because of city noise, it is a shame. You never know the frequency of the next groundbreaking event."
Deputy Industry and Information Technology Minister Chen Qiufa acknowledged at a conference in Shanghai in September that the telescope was regarded as a "landmark" project for the city. Since 2009, senior municipal officials have been visiting Songjiang district regularly, offering financial and administrative support. Located on a densely populated flat plain, thousands of people had to be relocated to make way for the project.
A restaurant owner living near the site said residents reluctant to move had had their houses demolished anyway. He said some residents were also concerned for their health, because the authorities had never explained the telescope's purpose or how it functioned.
"What we have heard from TV is that the telescope will help the local economy by bringing in lots of tourists," he said. "What we want to know, however, is the consequences of living in the shadow of a giant dish."
The project's total cost is a state secret, but according to state media, the Shanghai government was the second largest investor, after the Chinese Academy of Sciences. The third largest investor was the military.
The involvement of the military brought more trouble. State media said the telescope would serve China's military-controlled space project, with its ability to pick up long-distance signals, and the military's needs might override its civilian functions.
Shen confirmed that the military would use the telescope as an antenna for orbital calculations and data transmissions when sending spaceships to the Moon, Mars and beyond. On those occasions, scientific observations would have to be postponed.
Dr Hu Jian, an astrophysicist at Beijing's Tsinghua University, said Shanghai had been proposing the project to the central government for years, without getting approval. It was only after it teamed up with the military that the project was cleared for take-off.
"If it is mainly for military use I won't be surprised," Hu said. "Military communication uses a very narrow bandwidth that city noises would be unlikely to interfere with."
The dish's hasty construction has also prompted doubts about its quality. Construction was finished in about two years, while similar projects in other countries taking much longer to plan and build. "It is a bit fast, indeed," Hu said. "Similar projects in other countries have usually taken five to 10 years to finish."
Some astronomers doubt the telescope will be able to outperform much older dishes.
Wen said the Parkes radio telescope in New South Wales, Australia, for instance, would likely outperform the Shanghai one due to its quiet location and constant upgrading with the latest electronics. The 64-metre dish at Parkes was built in 1961 and is still at the forefront of astronomical discovery.
"What determines a telescope's performance nowadays is not the dish size but electronics such as signal converters and amplifiers," he said.
Shen admitted that Italy's Sardinia Radio Telescope, a 64-metre dish, could see more than the Shanghai telescope because of its higher-quality dish.
A researcher with the Chinese Academy of Sciences' Institute of Policy and Management said the Shanghai dish was under pressure to prove its scientific value because of the controversy about its location.
"I don't think the Shanghai government would have been so stupid to build a radio telescope as a 'face project' and I think it is too early to draw a conclusion," he said. "But if the dish fails to accomplish what it was designed to do and becomes just a tourist attraction, it will certainly stand out as a landmark of shame."