Modeling and Analysis of Terahertz Inter-Satellite Communication-Ranging System Under Platform Vibrations

Inter-satellite links (ISLs) are pivotal for information interaction and orbit determination in mega-constellation networks. Terahertz (THz) band, with its abundant spectral resources, exhibits significant potential for high-speed ISL establishment. However, due to frequent operations of Low earth orbit (LEO) satellites, the combined impacts of multi-source time-varying platform vibrations and two-dimensional asymmetrical features of each source on THz inter-satellite communication-ranging systems have yet to be revealed. This paper proposes a vibration-constrained THz-ISL system with LEO satellite attitude dynamics and spatial effects. Specifically, we establish a multi-peak frequency model using Semiconductor Inter-Satellite Link Experiment (SILEX) spectra, complemented by an optimized sum-of-sinusoids (SOS) time-domain model to address high dynamics and multi-source vibrations in LEO scenarios. Statistical link gain models are formulated, encompassing steady, sporadic, and universal scenarios. Subsequently, the proposed ISL gain model is applied to assess communication and ranging performance. We derive the signal-to-noise ratio (SNR)-vibration quantitative relationship through Stirling’s approximation, where SNR quantifies communication performance degradation. Ranging precision is evaluated via the Fisher information matrix (FIM), revealing vibration deterioration of Cramér-Rao bounds (CRB). Under given power constraints, we define truncation distance as the maximum vibration-tolerant link range where performance remains unaffected, and derive its closed-form solution. Simulations utilizing SILEX orbit data indicate that under typical settings: 1) inter-satellite vibrations are on the order of hundreds of μrad and cause a 5% pointing error attenuation; 2) vibrations alter system performance boundaries, with 600 km communication distance reduction and 2.2 dB ranging accuracy degradation with 0.03° deviation; and 3) vibration effects can be mitigated via phased array dimensions and beamforming design, achieving capacity-robustness trade-off.