Based on the ordered binary decision diagram (OBDD) theory

a new OBDD data structure in view of the characteristics of space telemetry

tracking and command system (TT&C system) was defined

and an approach to mission reliability analysis of repairable TT&C system was proposed. By dividing time windows of each station into phases

component logic relationship of each phase was analyzed

and the OBDD model of each phase was established. Then the final mission OBDD model was established by combining all single phase OBDD models together. Continuous time Markov chain (CTMC) was adopted to analyze the transition behaviors of each repairable component

and the mission reliability calculating algorithm was presented based on the new OBDD data structure. The result of a contrastive analysis with Markov method and simulation method reveals that: the proposed method can be used to analyze the mission reliability of repairable TT&C system accurately; the algorithm efficiency is higher than Markov method when there are more than 30 components.