UTCS: A Planet-Independent Atomic Coordinate-Time Representation for Interplanetary Systems

Universal Temporal Coordinate System (UTCS) This record contains the manuscript, reference documentation, and supporting materials for the Universal Temporal Coordinate System (UTCS), a deterministic atomic timestamp representation designed for distributed interplanetary systems. UTCS does not introduce a new metrological time scale. Instead, it defines a canonical hierarchical representation over existing atomic coordinate time scales (e.g., TAI, TT), aligned with the J2000.0 epoch. The goal is to provide a monotonic, integer-based timestamp layer suitable for delay-tolerant distributed mission architectures. Modern space systems simultaneously employ multiple time representations, including UTC (with leap seconds), TAI, TT, mission elapsed time (MET), spacecraft event time (SCET), and planetary local solar time (e.g., LMST). While atomic time scales are continuous, representation-level handling of leap seconds and conversion chains introduces complexity in distributed event ordering and long-duration archival systems. UTCS addresses this by: Representing elapsed SI seconds as a deterministic integer hierarchy. Separating atomic chronology from planetary environmental overlays. Confining leap-second adjustments to UTC conversion boundaries. Preserving strict monotonic ordering for distributed coordination. Maintaining compatibility with CCSDS 301.0-B-4 unsegmented time code (CUC) encoding. This record includes: The full manuscript (LaTeX and PDF). A CCSDS-aligned encoding profile. Numerical simulation demonstrating representation divergence under heterogeneous leap handling. Reference materials for integration into distributed space systems. The contribution of UTCS lies in architectural simplification and deterministic representation for interplanetary systems engineering — not in redefining established time standards.