Scientific Objectives and Payloads Configuration of China’s Tianwen-2 Asteroid Exploration Mission

Introduction: Asteroid exploration is a new frontier in Solar System exploration and a key research field for understanding its origin [1-7]. Building on the success of lunar and Mars exploration projects, China's Tianwen-2 (TW-2) asteroid mission is designed for a high scientific return. It will comprehensively investigate two distinct and scientifically valuable small bodies: the near-Earth asteroid 2016 HO₃ (Kamo'oalewa) [8-9] and the main-belt comet 311P [10]. This dual-target strategy is designed to address fundamental questions about the formation and evolution of our Solar System.

Scientific Questions and Objectives: The mission's scientific objectives are organized around five themes: characterizing the basic features of small bodies, understanding their origin and evolutionary history, exploring the origin of life and Earth's water, revealing solar influence, and investigating asteroids impact threats. For 2016 HO₃, a recently identified Earth quasi-satellite, the mission will determine its orbital parameters, rotation state, shape, size, and thermal radiation properties to study the origin and dynamical evolution of such rare co-orbital objects. Detailed mapping of its surface morphology, composition, and internal structure will provide essential context for the returned samples. Laboratory analysis of these samples will focus on physical properties, chemistry, mineralogy, and isotopic age, offering direct evidence to constrain Solar System formation models and the delivery of material to the inner planets. For main-belt comet 311P, the mission will perform similar measurements and study its unique orbit. Crucially, it will search for evidence of water and organic materials, and analyze its gas activity and near-space environment, which could provide key insights into the distribution of volatiles in the inner Solar System and the nature of transitional icy bodies.

Payload Configuration: To achieve these goals, the TW-2 mission carries ten scientific payloads. The remote sensing package is comprehensive: a visible and infrared imaging spectrometer (AVIRIS) for mineralogical mapping, a thermal emission spectrometer (ATES) for thermophysical property analysis, a multispectral camera (AMSCam), and a medium angle camera (AMAC) for high-resolution morphological and color imaging. Subsurface structure will be investigated by a core scan radar (ACSR). In-situ instruments include a Magnetometer (AMAG) to study remnant magnetic fields, a charged and neutral particle analyzer (CANPA) to characterize the solar wind interaction with the bodies, and a dust and volatiles analyzer (ADVA) to study dust and gas emissions from the main-belt comet. Additionally, a narrow angle camera (ANAC) and a laser detection and ranging (ALADAR) serve dual purposes for precision navigation and scientific observation. The technical specifications of these instruments, such as their spectral ranges, spatial resolutions, and detection sensitivities, are meticulously designed to fulfill the specific measurement requirements outlined for each scientific objective.

Characteristics of the Tianwen-2 Mission: TW-2 mission is distinguished by its pioneering target selection. It will perform the first dedicated exploration of an Earth quasi-satellite (2016 HO₃), investigating the origin and stability of this rare dynamical configuration. Simultaneously, it will conduct the first close reconnaissance of a main-belt comet (311P), a hybrid object that exhibits characteristics of both asteroids and comets, to study its volatile content and activity mechanisms. The mission employs a multi-phase strategy: remote sensing, in-situ analysis, and sample return from 2016 HO₃, followed by a flyby and remote sensing investigation of 311P. This integrated approach, combining sample return with detailed remote sensing of two unique small bodies, is expected to yield transformative results. The mission will advance our understanding of solar system dynamics, the nature and diversity of small bodies, the origin of Earth's water and prebiotic materials, and will demonstrate key technologies for future deep space exploration.

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