The construction of the 40 meter aperture radio telescope in Changbai Mountain, China will form an "equivalent aperture" of 3800 kilometers

Tech 2023-10-13 00:01:31 Source: Network

Source: China News NetworkBEIJING, Oct. 11 (Reporter Sun Zifa, Zheng Yingying) Following the launch of the construction of the Shigatse 40 meter radio telescope in mid September, the Shanghai Astronomical Observatory of the Chinese Academy of Sciences started the construction of the Changbai Mountain 40 meter radio telescope project on October 11

Source: China News Network

BEIJING, Oct. 11 (Reporter Sun Zifa, Zheng Yingying) Following the launch of the construction of the Shigatse 40 meter radio telescope in mid September, the Shanghai Astronomical Observatory of the Chinese Academy of Sciences started the construction of the Changbai Mountain 40 meter radio telescope project on October 11. The addition of these two telescopes can expand the longest baseline of China's VLBI network, known as the "equivalent aperture," to approximately 3800 kilometers, effectively improving observation sensitivity and spatial resolution, jointly undertaking the lunar exploration project phase IV and deep space exploration VLBI (Very Long Baseline Interferometry) orbit determination tasks, and promoting the development of China's radio astronomy scientific observation research.

On August 7, 2023, an aerial photo was taken of the site of the 40 meter caliber radio telescope in Changbai Mountain, and construction of a construction access road is underway. Courtesy of Shanghai Observatory, Chinese Academy of Sciences

Forming the "Six Stations and One Center" Observation Network

The project team of the Chinese Academy of Sciences (CAS) Shanghai Astronomical Observatory said that after the completion of the Xigaze and Changbaishan 40 meter radio telescopes, they will form the "six stations and one center" observation network of the Chinese Academy of Sciences Shanghai Astronomical Observatory together with the Shanghai 65 meter Tianma Telescope, the Shanghai 25 meter Sheshan Telescope, the Yunnan Kunming 40 meter Telescope, the Urumqi Nanshan 26 meter Telescope and the Shanghai VLBI Data Processing Center, To achieve the capability of "dual subnet and dual target" simultaneously, meeting the demand for simultaneous orbit measurement of two different detectors in different sky areas in China's subsequent deep space exploration mission planning.

The Changbai Mountain 40m Radio Telescope is located in the Ma'anshan Forest Farm of the Chixi District Management Committee of the Changbai Mountain Protection and Development Zone in Jilin Province. It is a full face, fully movable, high-precision, and multi-purpose horizontal radio telescope. In the future, it is planned to be equipped with a 7-band high sensitivity cooling receiver to achieve continuous spectrum coverage from 700MHz to 50GHz and simultaneous observation in the S/X dual frequency band, with the potential to upgrade to 86GHz observation.

To ensure the normal and stable operation of the telescope in the harsh cold environment of Northeast China, the Changbai Mountain 40 meter radio telescope is designed with integral insulation technology, and the main reflector back frame is wrapped with insulation material. At the same time, the antenna system adopts a full solid panel, with a single panel having a longitude better than 80 microns, a main reflecting surface having a longitude better than 0.3 millimeters, and a maximum pointing longitude better than 5 arcseconds.

Captured deep space targets 26 minutes early

The project team pointed out that due to the inherent characteristics of VLBI technology, the longer the distance (baseline) between telescopes, the larger the "equivalent aperture" of the formed "virtual" telescope, and the higher the sensitivity and spatial resolution of joint observation by multiple telescopes.

Two new 40 meter caliber radio telescopes will be built in Changbai Mountain in Jilin Province in northeast China and Shigatse in Xizang in southwest China. On the one hand, the existing VLBI network in China will be upgraded from "four stations and one center" to "six stations and one center", The maximum angular resolution has also been improved by 18%.

At the same time, compared to the longitude position of the Shanghai Tianma Telescope, the Changbai Mountain 40 meter radio telescope is closer to the eastern side of China's territory, increasing by 6.6 degrees to the east compared to the Tianma Telescope, and will capture deep space targets 26 minutes earlier than the Tianma Telescope.

In addition, the winter air in Changbai Mountain is dry and there are many sunny days, making it particularly suitable for telescopes to conduct high-frequency observations. This will enhance China's research capabilities in radio astronomy and promote more innovative achievements in a series of astronomical frontiers such as supermassive black holes, fast time-varying dense celestial bodies, gravitational wave electromagnetic counterparts, galactic dynamics research, and high-precision integrated reference frames.

The site selection has been carefully analyzed and determined

In December 2021, the fourth phase of China's National Deep Space Exploration Major Special Lunar Exploration Project was officially approved, which will carry out scientific exploration in the Antarctic region of the moon and provide preliminary exploration for countries to jointly build lunar research bases. In May 2023, the VLBI orbit measurement subsystem of the Chang'e-7 mission measurement and control system of the fourth phase of the lunar exploration project led by the Chinese Academy of Sciences Shanghai Astronomical Observatory was officially approved by the state, including the construction of a large radio astronomical telescope with a diameter of 40 meters and supporting observation stations in Shigatse, Xizang, and Changbai Mountain, Jilin.

As for why the Changbai Mountain 40 meter radio telescope was selected in Changbai Mountain, the Chinese Academy of Sciences Shanghai Astronomical Observatory pointed out that the site selection should comprehensively consider the rationality of the observation network configuration serving the orbit determination task of the lunar exploration project, the subsequent operation of the telescope, the difficulty of construction, climatic conditions, radio environment and other impacts. The project team, after many on-site surveys, carefully inspected several candidate sites in the northeast, After in-depth discussion and consultation with relevant parties, combined with future development plans around the station site, and careful analysis and judgment, it was finally determined to build a radio telescope in the Ma'anshan Forest Farm in Changbai Mountain, Jilin Province.

On August 19, 2022, the scene of the Changbai Mountain 40 meter caliber radio telescope site before construction. Courtesy of Shanghai Observatory, Chinese Academy of Sciences

The results of two engineering geological surveys in January 2020 and September 2022 also showed that the geological conditions of Ma'anshan Forest Farm in Changbai Mountain are superior and can meet the bearing requirements of the 40 meter radio telescope pile foundation. In August 2023, the Changbai Mountain 40 meter radio telescope project obtained a construction engineering planning permit and a construction permit. At the same time, geological survey and antenna design, the delineation and protection of radio quiet areas near the station site, meteorological and seismic conditions, forest fire prevention, and other work were also carried out in an orderly manner.

China's VLBI technology capability continues to enhance

According to the introduction of the Chinese Academy of Sciences Shanghai Astronomical Observatory, in January 2004, China officially launched the lunar exploration project. In 2007, the Chinese VLBI network was established under the support of the lunar exploration project - Chinese Academy of Sciences Shanghai Astronomical Observatory, based on its profound accumulation in the field of radio astronomy, applied real-time VLBI technology to the Chang'e-1 mission for the first time, organized the dominant forces of the Chinese Academy of Sciences affiliated observatories, and established the Chinese VLBI network consisting of "four stations and one center", Build a measurement and control system VLBI track measurement subsystem.

As an important component of China's lunar exploration project measurement and control system, the VLBI orbit measurement subsystem has successfully completed the three stages of lunar exploration project "orbit", "fall", and "return", as well as the VLBI orbit measurement mission for China's first Mars exploration mission. Since Chang'e-1, China's series of lunar and planetary exploration missions have adopted a new measurement orbit system of ranging and velocity measurement+VLBI, which has had a profound impact.

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