China unveils its Hubble telescope

Xuntian is one of China’s pivotal programs to become the world’s leading scientific power by 2050. timing is tight: the space telescope must be ready at the end of 2023 for a launch in 2024. For the first time, we have begun to see in recent weeks an image of the structure being assembled. This will lead to the integration of the various subsystems, mirrorsinstruments, then many tests before the final review.

The pandemic of the Covid-19 hitting China hard for several weeks, the work on the telescope is greatly disrupted.

Smaller than Hubble but covering more sky

Unlike the James Webb Space Telescope, Xuntian will be able to observe the Universe in the same wavelengths thatHubblethat is to say in the visible, the near infrared and theultraviolet. However, it will be a little less precise. Her resolution angular is supposed to be 0.15 second of arcagainst 0.1 for Hubble. It will also be less sensitive to light, with a mirror two meters in diameter. This is undeniably considerable, but remember that Hubble’s primary mirror measures 2.4 meters in diameter.

In contrast, Xuntian’s field of view is wider than that of Hubble. He will be able to see portions of the sky 300 times larger, and thus cover more targets. Xuntian should observe 40% of the visible sky. The data will be distributed among four research centers.

The Xuntian Space Telescope will not be assembled according to a traditional model. If Hubble is mounted according to a Ritchey-Chrétien scheme – a primary mirror concave and a secondary convex, Xuntian will use three spherical mirrors. The third is concave and will flatten the focal length and so get that wider field of view. This technique also reduces the aberrations optics.

Maintenance in orbit from the station

At the start of the project, Xuntian was to be attached to the current chinese space station being assembled. Eventually, the space telescope will be detached from the station but will remain on a orbit near. Thus, if there is a need to repair it, it will suffice to connect it to the station so that the Chinese astronauts can intervene.

China is anticipating the Hubble experiment, which required four in-orbit maintenance missions with the american space shuttle. These missions were complex and cost the American taxpayers dearly. The Chinese option is cheaper and guarantees the survival of the space telescope for as long as the station lives.

Before it is put into orbit, it will first be necessary to join the next two modules of the Chinese space station. For now, only the Tianhe module composes the station. Two additional modules (Wentian and Mengtian) are supposed to be affixed by 2023. After that, it will be the turn of the space telescope.

Fleet of space telescopes

Xuntian is far from the only space telescope planned. The Chinese space agency has designed a set for any field of observation: a solar telescope (ASO-S) on track, followed by a project of space telescope baptized Einstein and dedicated to the observation of the Universe in X-rays to study visible extreme events, or very heavy objects such as black holes. Last March, the project received approval from the Chinese Academy of Sciences to begin its construction. The launch is scheduled for 2023. With Xuntian, Chinese scientists plan to study different objects in the Universe: galaxies (training and development), clouds of gas and dust, stars and clusters of stars, and of course the Solar system.