CSST will have a field of view 350 times larger than Hubble . The telescope is the length of a three-story building and will be able to dock with the Chinese space station.
China hopes to launch itsbus-sized Xuntian space telescope by the end of 2023, which can be attached for maintenance to the space station already operated by Beijing.
Also known as the China Space Station Telescope (CSST), the new observatory in visible and ultraviolet light is expected to offer new insights into distant galaxies, mysterious dark matter and dark energy, and past and future evolutions of the universe.
The CSST is the length of a three-story building. It has a two-meter aperture, slightly smaller than the Hubble Space Telescope , but its field of view is 350 times larger than Hubble in area, said Liu Jifeng, deputy director of the National Astronomical Observatories of China (NAOC), in an interview with Xinhua.
“The field of view is the area of the sky that a telescope can see at the same time,” said Li Ran, project scientist for the CSST Scientific Data Reduction System . Hubble ‘s field of view is about 1 percent the size of a fingernail at arm’s length, so the telescope, in its thirties, saw only a tiny fraction of the sky, Li added.
The CSST , under construction, has a three-mirror anastigmatism design that helps it achieve superior image quality within a wide field of view, according to the researchers.
Furthermore, it is an unobstructed Cook-type off-axis telescope that can, in principle, achieve better accuracies in photometry, position, and shape measurements when sampled correctly.
“It has an advantage for survey observations in that it can scan a large part of the universe quite quickly,” said Zhan Hu, project scientist at the CSST Optical Facility .
The CSST will be installed with five instruments, including an inspection camera. The camera’s main focal plane is equipped with 30 81-megapixel detectors that will image and spectra over approximately 17,500 square degrees of galactic mid-to-high latitude and mid-to-high ecliptic latitude sky in multiple bands, according to the researchers.
Four other instruments mounted on the CSST are designed to observe individual objects or small fields, such as mapping star-forming regions of the Milky Way, obtaining instant color of rapidly varying objects such as comets and spinning asteroids, studying the co-evolution of supermassive black holes and galaxies and star formation in the near part of the universe, and direct images of exoplanets in the visible.
CSST is likely to be the largest space telescope for visible and near-ultraviolet astronomy in the decade before 2035, Zhan said.
Li used the analogy of photographing a flock of sheep to explain CSST’s capabilities. ” Hubble can see one sheep, but CSST sees thousands, all at the same resolution,” he said.
Flying with the space station
The telescope , during its normal observations, will independently fly in the same orbit as the China space station , but will remain at a great distance. China plans to complete the construction of its space station in orbit by 2022.
Zhan said the telescope was designed, in its initial plan, to be mounted on the space station , but there would be drawbacks such as vibration, potential contamination, stray light and obstruction of the line of sight from the space station. Later, a bold design was adopted: placing the telescope in the space station ‘s orbit , but keeping them far apart from each other during normal operations, and docking with the space station when necessary.
CSST can dock with the space station for refueling and servicing on schedule or as needed, making it more affordable to maintain than Hubble.
The CSST is expected to start science operations in 2024 and has a nominal mission life of 10 years, which could be extended in principle.
The CSST will take pictures of 40 percent of the sky and transmit massive data to Earth that scientists around the world can study, Li said, adding that its main goal is to tackle the most basic problems about the universe.
It will observe more than a billion galaxies and measure their positions, shapes and brightness, which may help explain how those galaxies evolve.
