Digital twin used to test space telescope

Before it even reaches orbit, China's newest space telescope is already exploring the universe through a complex digital rehearsal.

Scientists have spent six years building a sophisticated simulation system that creates "pixel-perfect" data that mimics what the telescope will see at a pixel level to test the Chinese Space Station Survey Telescope.

This digital twin allows researchers to solve technical problems on the ground before the hardware ever leaves Earth.

The CSST is a flagship project for China's space program. Featuring a 2-meter aperture — the opening that lets in light — it is designed to be a "super eye" in the sky.

While it has a similar resolution to the Hubble Space Telescope, its field of view is 300 times larger, allowing it to photograph much bigger patches of the sky at once.

The details of the simulation system were published in the journal Research in Astronomy and Astrophysics on Wednesday.

"Once launched into orbit, fixing the telescope would be extremely expensive. Therefore, we must eliminate as many errors as possible through ground testing and software corrections," said Chang Jin, an academician at the Chinese Academy of Sciences.

Chang described the computer system as a "rehearsal" that provides a repeatable way to test the telescope's reliability.

The simulation is particularly vital for the telescope's main camera, which must survive the harsh conditions of outer space.

In orbit, the camera faces challenges like uneven solar heating, where the sun's rays heat one side of the instrument more than the other and cause components to expand.

It also contends with structural deformation, a process where changes in gravity and temperature can slightly warp the telescope's frame. Additionally, the system must account for imaging jitter, which are tiny vibrations that can cause the telescope's high-resolution pictures to appear blurry.

By combining thermal and structural models into the software, the team can predict how these issues will affect the images and adjust the design to compensate.

The system also simulates how cosmic rays — high-energy particles from deep space — might damage the telescope's sensors over time.

Once it begins its mission, the CSST is expected to survey 17,500 square degrees of the sky — nearly 40 percent of the entire firmament — and detect billions of galaxies.

This will create a massive amount of information.

Scientists expect to collect nearly 100 petabytes of data — roughly the same amount of storage found on 20 million DVDs. Processing that much data with high precision will be a major hurdle for astronomers.

The simulation system is currently being used to push the data processing software to its limits to ensure it can handle the workload after launch.

"With code and pixels, we have etched the future's starlight onto hard drives in advance," Chang said. "As the CSST opens its 'eye', we will embark on a new era of big-data astronomy."

limenghan@chinadaily.com.cn