China’s first solar exploration satellite sent into space

China’s first solar exploration satellite named Xihe was sent into space aboard the country’s Long March-2D carrier rocket from the Taiyuan Satellite Launch Center in north China’s Shanxi province on Oct. 14.

The satellite is expected to fill in the gap in high-quality observation data on the source regions of solar eruptions by conducting the world’s first space exploration of solar Hα spectral imaging.

The sun-probing science and technology experiment satellite, whose main scientific payload is a solar space telescope, weighs 508 kg and has a designed lifespan of three years. It will operate in a sun-synchronous orbit at an altitude of 517 km and with an inclination of 98 degrees, which allows it to go over Earth’s North and South Poles and carry out 24-hour continuous observation of the sun.

The solar Hα spectral line is one of the most useful spectral lines for the study of the responses of the photosphere and chromosphere to solar activities.

Through data analysis of the spectral line, scientists can get information about physical changes in the sun during solar eruptions, such as its atmospheric temperature and velocity, and study the dynamic processes and physical mechanisms of solar eruptions.

With the rapid development of aerospace technology, more than 70 satellites have been sent into space globally for solar observation since the 1960s. They have focused on observational studies of sunspots, solar flares, and coronal mass ejections.

“Exploring and studying solar activities and coming up with countermeasures can reduce or avoid their adverse impact on the Earth,” said Zhao Jian, director of the Earth Observation System and Data Center of the China National Space Administration (CNSA), who believes it absolutely necessary for China, a major country in aerospace, to carry out solar exploration in time.

The country has formulated two solar exploration projects, which were named after Xihe, the sun goddess in charge of time and calendar in ancient Chinese mythology who has been well known as the mother of the sun, and Kuafu, a giant in Chinese mythology who chased after the sun, according to Zhao, who said the projects represent China’s solutions and contributions to solar exploration.

While the recently launched satellite Xihe represents China’s first step toward solar exploration, the Kuafu mission is designed to develop and launch another solar observation satellite—the Advanced Space-Based Solar Observatory. As part of the space-science pilot project of the Chinese Academy of Sciences (CAS), the Kuafu mission is scheduled to be launched in 2022.

The successful launch of Xihe marks China’s official entry into the era of solar exploration, Zhao said, adding that the satellite bears great significance as it will conduct the world’s first space exploration of solar Hα spectral imaging and involve new methods and new technologies for astronomical velocity measurement and navigation based on spectral information.

Solar exploration has become a hotspot of global space exploration missions. China ranks second in the world in terms of the number of published research papers on solar observation, but all the satellite-generated data used by Chinese scientists came from foreign spacecraft, according to Zhao.

“Xihe will put an end to such dependence on foreign satellites,” said Zhao, adding that China will establish a scientific committee on satellite data and formulate policies on the data so that it can be studied, used and shared by scientists around the world.

“We will strive to achieve original research results and make contributions to the advancement of science,” Zhao said.

Xihe has adopted a groundbreaking new technology satellite platform which realizes the ultra-high pointing accuracy and stability of the payload and is two orders of magnitude better in terms of relevant performance than other existing satellite platforms with the same moment of inertia.

Dubbed “double ultra-high platform” by industry insiders, the platform is expected to give a boost to leapfrog development of technologies for high-precision satellite platforms in China.

According to Zhao, upon the success of in-orbit tests, the high-performance technology platform will significantly improve China’s technological strength for space observation.

Relevant technologies of the platform will be promoted in the next-generation space missions involving high-resolution detailed survey of the Earth, large-scale stereoscopic mapping, stereoscopic solar exploration, and the discovery of exoplanets, Zhao said.

Two intergovernmental cooperation microsatellites of the Asia-Pacific Space Cooperation Organization (APSCO), the first international organization in the high-tech industry proposed by China, and eight commercial microsatellites have also been launched together with Xihe.

The two microsatellites of the APSCO will mainly verify technologies concerning the performance of coiled extension arm and interplanetary communications. Their launch marks the first time that the organization has sent satellites into space.