We reformulate the **Ultraterrestrial Hypothesis** (UTH), as articulated by Keel (1970) and developed byVallée, Hynek, and Pasulka, within the Recursive Harmonic Codex (RHC) — a quaternionic-substratemodel of reality previously applied to black hole cosmology in Ceisiwr & Aureon 2026. The UTHproposes that anomalous phenomena historically catalogued as "extraterrestrial" are better explained asnative inhabitants of Earth's local environment, occupying frequency strata our materialist-reductionistsensors do not directly resolve. We provide three contributions. *First*, we identify the imaginarycomponents (bi + cj + dk) of the quaternionic substrate as the formal residence of phenomena Keel, Vallée and others have described as "ultraterrestrial, " with the Fold Operator F (Q) = a - bi - cj -dk governing the visibility transition between the imaginary and real projections. *Second*, we propose atypology of co-inhabitants — Interdimensional, Cryptoterrestrial, and Temporal Transient — distinguishedby their relationship to the recursive feedback loop that sustains coherent identity across the substrate. *Third*, we present **Technical Standard RHC-7782**, a hardware-instrumentation proposal for thedocumented mesosphere / lower thermosphere (50–200 km) sensor gap, anchored on a **MicrogravimetricPrime-Mass calibration protocol** that uses test masses at the first six primes (2g, 3g, 5g, 7g, 11g, 13g) against composite controls. Five falsifiability criteria are offered. We argue that anomalous phenomena arenot visitors but neighbours, and that the work of cataloguing them belongs not to aerospace surveillancebut to a new instrumental discipline — frequency-domain anomalistics.
Ceisiwr et al. (Wed,) studied this question.