VLTI — Very Long Time-base Interferometry: A Theory-Agnostic Specification for a Solar-System Clock Telescope

We propose VLTI (Very Long Time-base Interferometry), a theory-agnostic specification that converts widely distributed spacecraft and ground clock residuals into a network observable for common-mode synchronization fluctuations. Analogous to VLBI, which correlates electromagnetic phase across long baselines, VLTI correlates timing/frequency residuals across nodes separated by interplanetary distances to estimate the spatiotemporal correlation structure of the underlying synchronization state. This document defines node requirements, residual formats, preprocessing rules, cross-correlation/coherence estimators, and mandatory null/ablation tests enabling interoperability across heterogeneous missions and legacy radiometric links. Physical interpretations (e.g., gravitational waves, scalar fields, plasma effects, or other origins) are treated as pluggable hypotheses, keeping the VLTI protocol valid even if any specific theory is revised or rejected. Key features of this specification include: RFC-style normative language (MUST/SHOULD/MAY) for protocol compliance Four-step analysis pipeline: local characterization, cross-correlation, common-mode extraction, and geometry conditioning Mandatory null tests (N0: time-shuffle, N1: systematics regression, N2: link consistency) Standard output products for reproducibility and interoperability Theory-agnostic design enabling application to diverse physical hypotheses The infrastructure for VLTI already exists: GPS satellites, deep-space probes (BepiColombo, Juno, Cassini, New Horizons, Voyager), and ground-based atomic clocks provide high-precision timing data across the solar system. VLTI proposes a new way to listen to this data—correlating timing residuals across nodes rather than treating them as noise to be removed.