Noise and Index Decomposition of Taiji-2 Interferometer System

The Taiji program for space-based gravitational wave detection is a mission initiated by the Chinese Academy of Sciences to explore gravitational waves in the mHz frequency band. It consists of three satellites orbiting the Sun in an equilateral triangle formation with an arm length of 3×10⁶ km, employing laser interferometry to measure picometer-level displacement fluctuations between satellites. As a pivotal link in Taiji’s “three-step” development strategy, Taiji-2 will comprehensively validate all key technologies of the program. The satellite configuration of the Taiji-2 satellite shares the same configuration as Taiji-3, with its laser interferometry system requiring a noise level of 30 pm·Hz^–1/2 as the core measurement technique. This paper systematically decomposes the top-level requirements into subsystem noise budgets and key parameters, including the laser system, interferometer optical bench, phasemeter, telescope, and breathing angle compensation mechanism. The research findings establish a theoretical foundation for subsequent engineering task allocation in the Taiji-2 mission.