Key testing was successfully completed on September 27, enabling the Daocheng Solar Radio Telescope (DSRT), a solar telescope array in southwest China’s Sichuan province, to be officially put in to use. (PHOTO: XINHUA)

By Staff Reporters

It’s all systems go for the world's largest synthesis aperture radio telescope. Key testing was successfully completed on September 27, enabling the Daocheng Solar Radio Telescope (DSRT), a solar telescope array in southwest China’s Sichuan province, to be officially put in to use, according to the Chinese Academy of Sciences (CAS).  

The telescope array is a milestone in the country's space environment ground-based comprehensive monitoring network (phase-2 Meridian Project) and will provide high-quality observation data for solar physics and space weather research in China. 

Three hundred and thirteen antennas 

The sun brings us heat and light, but solar activities also cause space weather on Earth, which can have a serious impact on high-tech systems in space and on the ground, said Yan Jingye, director of the project from the CAS. 

The DSRT is designed to precisely monitor and predict space weather. It is like a "radio camera" taking pictures of the sun, forecasting and giving warnings about space weather, while providing first-hand information for scientific research. 

The telescope array consists of 313 six-meter-wide antennas. The antennas are evenly distributed on a one-kilometer-diameter circle, and a 100-meter-high calibration tower at the center sends calibration signals to all the antennas.  

The 313 antennas work in collaboration and form a huge, virtual telescope at the frequency range of between 150 to 450 megahertz to achieve high-precision imaging of solar events. This includes solar eruptions and the process of solar storms entering interstellar space, which helps to predict and assess the impact of solar activities on Earth. 

Every day when the sun rises, all antennas aim at and turn with the sun, like gigantic sunflowers. After sunset, the array begins its other tasks, such as the detection of space debris, pulsars and satellites in geostationary orbit, said Yan. 

Meet the challenge

Converting scientific solutions into reality involves a lot of technical and construction issues. In addition, the high altitude of Daocheng and its extreme weather conditions presented major challenges for the equipment design and testing, said Wu Junwei, executive manager of the DSRT. 

In order to ensure quality and meet the construction deadlines, the research team adopted a "three-step" development scheme of the telescope array. Firstly, they started by using two units (antennas) to verify the technology, and then using 16 units to conduct imaging experiments, before finally carrying out the 313-unit system construction and testing. 

When the array is built with 16 units, the observation effect exceeds that of similar equipment in other countries, said Wu Lin, deputy chief designer of the DSRT. Since March 2022, the telescope array’s 16-unit imaging experimental system has begun to acquire solar imaging data, and accumulated a large number of solar activity images and spectrum data. 

The whole system testing showed that the telescope array had achieved continuous and stable solar radio imaging, spectrum observation capabilities with a maximum field of view of ten solar radii, and all technical indicators met or exceeded design requirements, according to the CAS. 

Joint observation 

In May, a joint observation experiment was carried out by the DSRT and the Low-Frequency Array in the Netherlands to achieve cross-validation. In July, the telescope array was able to offer high quality continuous and steady monitoring of solar activities, and the radio astronomy observation capabilities such as pulsar imaging were also preliminarily verified. 

According to Yan, the telescope array will also conduct joint observations with other major national scientific and technological infrastructure, including the FAST telescope (China Sky Eye) in Guizhou province, China's deep-space observation radar facility (China Compound Eye) in Chongqing municipality, and Sanya Incoherent Scatter Radar in Hainan province. 

Yan added that both DSRT and FAST have their own advantages, and can play a greater joint role. 

The FAST, with a 500-meter aperture, is the most sensitive radio telescope in the world. It is very good at observing pulsars and fast radio bursts, but it does not have all-sky scanning capability, said Yan. Meanwhile the DSRT can perform like a radio camera through 313 antennas, which can continuously shoot video for radio sources such as the sun, said Yan, adding that the telescope array has a better ability to determine the coordinate position of fast radio bursts. 

"We will continue to optimize and upgrade the telescope array, and hope to achieve the 100-kilometer scale,” said Yan.