Based on the observability analysis of the measurement model under the modern control theory

this paper proposes the observability problem of the absolute clock state measurement model. It is inspired by measured state vector space and state vector algorithm

and transformed into the isomorphic mapping principle of vector space essentially. It establishes the minimum mean square error (MMSE) observable decoupling measurement model under equivalent transformation with basic measurement unit (BMU). This method reveals the essence of symmetric measurement performance under two-way message exchange

and realizes Kalman filtering algorithm for clock state tracking under the necessary conditions that the measurement model satisfies the observability. The proposed algorithm does not depend on the optimized initial point setting

the initial point selection is robust

and it is also robust to changes in network connectivity. The simulation results show that the observable measurement model can achieve scale expansion

and the proposed algorithm has local and global uniform of MMSE measurement performance

which is close to the boundary of the Bayesian Cramer-Rao lower bound (CRLB) measurement performance.