China’s Tianwen-2 mission
Gauri Gupta

On 28 May, China’s Tianwen-2 spacecraft successfully launched a Long March 3B/E rocket from the Xichang Satellite Launch Center in China. The spacecraft deployed its solar arrays 18 minutes after liftoff and entered a trajectory to escape Earth’s gravitational pull, creating a significant advancement in the country’s deep space exploration efforts.

Background to Tainwen
Tianwen's program comprises a set of interplanetary missions that aim to improve the capabilities of space exploration in China. The Chinese philosophy and poetry “Qu Yuan” pose a classical poem that encapsulates the essence of China’s scientific goals in space exploration. The excerpt “Heavenly Questions” is the equivalent of “Tianwen,” which serves as the title of the poem.
 
In 2018, Tianwen-2 was proposed as part of the deep space exploration program by the Chinese Academy of Sciences. Subsequently, Zhouzhai Orbiting Center underwent a series of scheduling adjustments, which called for a programmatic change to its launch schedule from 2022 to 2025. The China Academy of Space Technology (CAST) was responsible for the construction of the spacecraft, which developed a 2100 kg mass space vehicle designed to operate for 10 years after its deployment. It is the first time a Long March-3B rocket has been used to reach the second cosmic velocity (over 11.2 km/s), enabling the spacecraft to escape Earth's gravitational field. The China National Space Administration (CNSA) executed advanced autonomous guidance and terminal correction systems to maintain the spacecraft's precise trajectory and to meet the demand for high precision.
 
It is China’s first trial of high-speed atmospheric reentry. The return capsule is expected to withstand reentry speeds of up to 12.1 km/s. This mission builds on the achievements of Tianwen-1, which successfully orbited and landed on Mars in 2021. The future missions include Tianwen-3, which will focus on returning samples from Mars, and Tianwen-4 is aimed at exploring Jupiter and Uranus.
 
What are its Objectives?
First, asteroid sample collection from Kamoʻoalewa. It aims to collect at least 100 grams of material, which includes organic compounds and minerals, from the surface of Kamoʻoalewa, a small asteroid measuring approximately 40 to 100 meters in length. It is considered to be a “living fossil” of the solar system. The asteroid has a unique orbit, and its composition suggests it could be a fragment of the Moon.
 
Second, reaching comet 311P/PANSTARRS. After the sample return, Tianwen-2 will journey to 311P/PANSTARRS, a main-belt comet between Mars and Jupiter, exhibiting both asteroid and comet characteristics.  The spacecraft will conduct remote sensing to analyze the comet's composition, activity, and potential for harboring volatiles, contributing to the understanding of the early solar system and the origins of water on Earth.
 
Third, testing technological innovation. The mission will test innovative sampling techniques, including the anchor-and-attach method, which involves the spacecraft anchoring itself to the asteroid's surface to collect samples. This technique requires precise autonomous navigation due to the time delay in communications between Earth and the spacecraft.
 
Fourth, carrying scientific payloads. It carries 11 scientific instruments, which include multispectral and infrared spectrometers, high-resolution cameras, a radar sounder, a magnetometer, and dust and gas analyzers.  These instruments will study the surface composition, geological features, subsurface structures, magnetic fields, and interactions with solar wind at both Kamoʻoalewa and 311P/PANSTARRS.