Progress of the Earth 2.0 space spacecraft system design

Abstract

The Earth 2.0 (ET) mission is a next-generation Chinese space mission aimed at detecting thousands of Earth-sized planets, including habitable Earth-like planets around solar-type stars (Earth 2.0s), cold low-mass planets, and free-floating planets. ET will carry six 28 cm transit telescopes, each with a 550 deg² field of view, and one 35 cm microlensing telescope with a 4 deg² field of view. The stringent requirements for ultra-high-precision transit photometry and long-term microlensing monitoring impose demanding constraints on the spacecraft’s stability and performance. ET is scheduled to enter Phase C in 2026. During Phase B, the spacecraft system underwent detailed design and optimization, with key updates to better meet the scientific requirements. These include improvements to the overall configuration, pointing stability, data downlink capability, and other aspects. Notably, the pointing stability requirement has been tightened by more than an order of magnitude. This paper report recent progress in the ET spacecraft system design, highlighting the scientific drivers and associated engineering trade-offs. The increased pointing stability requirement has driven major enhancements in the measurement and control architecture of the Attitude and Orbit Control System (AOCS), as well as optimized thermo-elastic control of the optical bench. In addition, telescope layout and overall configuration have been optimized to minimize mitigate stray light during long-term observations. The data transmission system has been selected to maximize scientific downlink capacity without interrupting the observation cadence.