Key Takeaways:

  1. China is poised to launch the Xuntian spacecraft, a significant project aimed at advancing the nation’s astronomical research and leveraging its space station capabilities.
  2. The Xuntian spacecraft, also known as the Chinese Survey Space Telescope or the Chinese Space Station Telescope (CSST), is equipped with a two-meter diameter primary mirror and is scheduled for launch this year.
  3. With a mission lifespan of 10 years, Xuntian is designed to surpass the capabilities of NASA’s Hubble Space Telescope and conduct breakthrough observations in cosmology, dark matter, dark energy, the Milky Way galaxy, star formation, evolution, and exoplanets.
  4. Xuntian boasts a 2.5 billion-pixel camera and a field of view over 300 times larger than that of Hubble, enabling it to capture high-definition panoramic views of the universe.
  5. Despite optimism about Xuntian’s potential, there are lingering questions about its capabilities compared to Hubble, including concerns about spectral resolution, data calibration, and peer-reviewed access to observing time.

China is preparing for a significant initiative that not only enhances the nation’s astronomical research program but also strengthens the utilization of its space station complex.

Moreover, there is considerable pride associated with China’s ambitious endeavor. The spacecraft, named Xuntian, is also referred to as the Chinese Survey Space Telescope or the Chinese Space Station Telescope (CSST). The term “Xuntian” translates to “surveying the sky” or “survey of the heavens.”

Expected to be launched this year, the CSST, which is about the size of a bus, accommodates a primary mirror with a diameter of two meters (6.6 feet). This space telescope, operating in the ultraviolet-optical spectrum, is intended to co-orbit with China’s Tiangong space station. While its planned mission lifespan is 10 years, there is potential for the observatory’s space activities to be extended.

Xuntian aims to surpass the capabilities of NASA’s Hubble Space Telescope. Positioned near China’s space station, this sizable orbiting facility will be accessible for periodic maintenance by Chinese astronauts.

Lin Xiqiang, deputy director of the China Manned Space Agency, anticipates that the Xuntian observatory will achieve breakthroughs in cosmology, dark matter and dark energy studies, research on the Milky Way galaxy and neighboring galaxies, investigations into star formation and evolution, and the exploration of exoplanets.

This is an ambitious agenda indeed. Lin highlighted that the high-resolution telescope will conduct deep-field survey observations covering an area of 17,500 square degrees, in addition to conducting detailed observations of various celestial bodies. Xuntian is equipped with a 2.5 billion-pixel camera.

Field of view

Scheduled to be launched into Earth orbit next year via a Long March 5B rocket, Xuntian will be capable of capturing high-definition panoramic views of the universe with spatial resolution comparable to the Hubble Space Telescope. However, China’s orbital observatory boasts a field of view over 300 times larger than that of Hubble. The field of view refers to the portion of the sky visible to a telescope at any given time.

Li Ran, project scientist of the CSST Scientific Data Reduction System, used an analogy involving imaging a flock of sheep to illustrate the capabilities of CSST during an interview with China’s state-run Xinhua news agency last year. “Hubble may see a sheep, but the CSST sees thousands, all at the same resolution,” Li remarked.

Furthermore, this advanced telescope will remain in the same orbit as the space station for prolonged independent flight and observations. It is designed to periodically dock with the space station for maintenance, supply, and upgrades by Tiangong astronauts, according to Lin.

Cutting-edge technology

Zhou Jianping, chief designer of China’s manned space program, also praised the planned capabilities and contributions of Xuntian during an interview with China Central Television (CCTV).

“The Xuntian telescope represents the most significant scientific project since the inception of our country’s space station program. It is a highly anticipated scientific facility within the Chinese astronomical community and symbolizes the state-of-the-art technology in astronomy at the national level,” Zhou remarked.

He added that the telescope is the most advanced among ongoing telescope research projects worldwide in terms of its ability to produce ultraviolet spectrum images. It is expected to significantly advance astronomy research in China to an internationally leading level and empower Chinese astronomers to become prominent figures in the field.


According to Li Chengyuan from the School of Physics and Astronomy at China’s Sun Yat-sen University, both the China Space Station Telescope and NASA’s Hubble Space Telescope are sensitive to a similar wavelength range.

However, Xuntian possesses a field of view approximately 5 to 8 times wider than that of Hubble, as emphasized by Li last year in the journal Research in Astronomy and Astrophysics.

The “first-generation” Xuntian space telescope comprises five observation instruments, including the Xuntian module, the terahertz module, the multichannel imager, the integral field spectrograph, and the extrasolar planetary imaging coronagraph.

The Xuntian module, featuring a wide field of view camera, will be allocated a significant portion of observation time.

Testing and assembly

During standard observations, the space telescope will operate independently in the same orbit as China’s space station, albeit at a considerable distance.

“We are currently in the process of developing the prototype sample. We have completed the development of all subsystems, components, and units, and we are preparing for testing after assembly,” stated Xu Shuyan, chief designer of the Xuntian optical facility and researcher at the National Astronomical Observatories of the Chinese Academy of Sciences.

“After this phase, we will commence the development of the telescope sample and initiate research on the flying components. Subsequently, we will conduct joint testing with the Xuntian platform and tests at the launch base before the launch,” Xu explained to CCTV.

China’s space station is to serve as a maintenance hub for the country’s Xuntian space telescope. (Image credit: CMSE)

World-class hub

When it comes to pushing the boundaries of space astronomy on a global scale, one cannot overlook the accomplishments of the Space Telescope Science Institute (STScI) in Baltimore, Maryland. STScI serves as a multi-mission science operations center for NASA’s flagship observatories and is a leading astronomical research center worldwide.

STScI hosts groundbreaking scientific programs utilizing the James Webb Space Telescope, the Hubble Space Telescope, and will operate as the science operations center for the Nancy Grace Roman Space Telescope, slated for launch in the mid-2020s.

Located on the campus of Johns Hopkins University in Baltimore, Maryland, STScI is managed by the Association of Universities for Research in Astronomy on behalf of NASA.

Unanswered questions

While Chinese space agency officials are optimistic about the capabilities of Xuntian, some researchers harbor reservations.

“For facilities open to the international scientific community, such as Hubble or Webb, we provide extensive documentation and software to facilitate outstanding scientific programs,” noted Tom Brown, an astronomer and head of the Hubble Mission Office at STScI.

“In contrast, there is limited public information available regarding the specific capabilities of the China Space Station Telescope, making it challenging to assess its potential for enabling similar investigations,” Brown informed

Based on the limited information available, Brown suggested that China’s Space Station Telescope may offer a larger field of view than Hubble but with a smaller mirror, resulting in less collecting area and spatial resolution. Additionally, the spectral resolution appears to be lower than that of Hubble, and CSST does not extend into the far-ultraviolet range, below 200 nanometers.

“There remain numerous unanswered questions at this juncture,” Brown remarked, including the successful launch of the space-based telescope, its maintenance in a space station environment, the peer review and allocation of observing time, and the calibration of data.

“Hubble continues to lead the field in all aspects of a world-class research facility, undertaking groundbreaking projects across the spectrum of astrophysics,” Brown concluded. “I am eager to see how the story of the China Space Station Telescope unfolds.”

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