天问二号，向小行星进发！

Core Points - The Tianwen-2 mission successfully launched on May 29, 2025, aiming to explore and collect samples from asteroid 2016HO3 and later conduct scientific investigations on main-belt comet 311P [1][2][8] - The mission includes 13 flight phases, with the spacecraft expected to reach distances of approximately 150 million to 500 million kilometers from Earth [1][4][11] Mission Objectives - The primary goal is to collect samples from asteroid 2016HO3 and return them to Earth, marking a significant milestone in asteroid exploration [2][9] - The mission aims to advance key technologies such as sampling from low-gravity bodies, high-precision autonomous navigation, and small-thrust orbital transfer design [2][4] Scientific Goals - The scientific objectives focus on determining various physical parameters of the asteroid and comet, including orbital parameters, rotation characteristics, shape, size, and thermal radiation properties [2][3] - The mission will also analyze the samples to study their physical properties, chemical and mineral compositions, isotopic makeup, and structural characteristics, contributing to research on the early formation and evolution of the solar system [2][3] Technological Innovations - The Tianwen-2 spacecraft is equipped with 11 scientific instruments, including cameras and spectrometers, to facilitate data collection [3][4] - The mission employs a "fly while explore and decide" strategy to enhance the spacecraft's autonomy and adaptability to the unique characteristics of the target asteroid [6][11] Launch Vehicle - The Long March 3B rocket, which has successfully completed 108 launches, was used for this mission, marking its first execution of an Earth-escape trajectory [7][11] - The rocket's launch speed reached 11.2 kilometers per second, requiring high precision to ensure successful orbital insertion [7][11] Challenges and Comparisons - The Tianwen-2 mission presents unique challenges compared to the Tianwen-1 Mars mission, particularly in sampling under low-gravity conditions and the vast distances involved [10][11] - The average diameter of asteroid 2016HO3 is approximately 41 meters, posing difficulties in achieving stable attachment and sampling due to its weak gravitational field and high rotation speed [10][11]