China is building the world’s largest steerable telescope, called QTT

The giant eye on the sky will be able to point in any direction over the northern hemisphere when completed in about six years
Project led by the Xinjiang Astronomical Observatory will help answer scientific questions and guide China’s space exploration

Science

Ling Xinin Ohio

Published: 9:00pm, 22 Sep 2022

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Construction of the world’s largest fully steerable radio telescope began on Wednesday in western China’s Xinjiang region.

Chinese astronomers said the Qitai radio telescope (QTT) will help address a range of questions, from star formation to the detection of gravitational waves, black holes and dark matter.

The telescope will also support China’s exploration of the moon, Mars and beyond by providing tracking services to rockets and spacecraft, with its 110 metre (360 feet) diameter dish able to point in any direction of the northern hemisphere sky.

QTT will surpass the Robert C. Byrd Green Bank Telescope in the US, which has a 100 metre (328 feet) diameter steerable dish.

At a groundbreaking ceremony in Qitai county, officials said the project – led by the Xinjiang Astronomical Observatory – would take about six years. QTT is mainly funded by the Chinese Academy of Sciences and local governments and is the region’s first big science facility.

Astronomer Wu Xuebin from Peking University, who attended the ceremony virtually from Beijing, said the project means a lot to the region, in terms of attracting world-level talent and boosting socio-economic development.

“We have seen strong support from the local governments and I’m confident in the telescope’s construction and operation,” he said.

A groundbreaking ceremony in China’s Xinjiang region on September 21 signalled the start of construction on QTT which will be the world’s largest steerable radio telescope. Photo: Handout

China already runs the world’s largest radio telescope – the Five-hundred-metre Aperture Spherical radio Telescope (FAST) – which sits in a natural depression in the southwestern mountains of Guizhou.

But FAST’s reflective surface is more or less fixed, limiting the area of sky it can see, Wu said. QTT’s ability to rotate in all directions and its unprecedented diameter would “make another major contribution to the world”.

QTT’s position in a sparsely populated rectangular basin, surrounded on all sides by mountains, will keep radio noise to the barest minimum. Its elevation at about 1,800 metres (5,900 feet) will also keep conditions dry, so that water vapour does not interfere with observations.

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The QTT’s specifications were outlined in 2014 by its chief scientist Wang Na, who is also director of the observatory.

In a paper published in China’s Scientia Sinica Physica, Mechanica & Astronomica journal, Wang said QTT would have an active surface – like the Green Bank Telescope – adjusted by small motors called actuators at the back of the dish.

Wang’s team designed and developed large-scale, parabolic antennas, inertia control for very accurate pointing, multi-band receivers and shielding against radio noise, all aimed at achieving a frequency range of 150 megahertz to 115 gigahertz, she wrote.

The FAST telescope’s chief scientist Li Di paid tribute to the “ambitious and fantastic” QTT project.

“Like FAST, it represents a leap in core capacity. Just like FAST, the project has and will have to overcome enormous obstacles. I am just happy for the team, particularly Wang Na, whose tenacity makes the project possible,” Li said.