Multi-Path Validation Dataset for ERA5-Derived Atmospheric Refraction Coefficient (κ): Path 5 — Cerro Champaquí–Aconcagua

Overview This deposit is the fifth entry in a multi-path validation panel supporting Real-Time Atmospheric Refraction Coefficient Determination Using ERA5 Reanalysis Data for Line-of-Sight Visibility and Geodetic Applications (Alkalali, K.Z.A., under revision, Geodesy and Geodynamics, manuscript GEOG-D-26-00098R1). Companion to Path 1 (Sağrak–Shkhara, DOI: 10.5281/zenodo.21413841), Path 2 (Pic de Finestrelles–Pic Gaspard, DOI: 10.5281/zenodo.21420699), Path 3 (Łysa Góra–Warsaw Mokotów, DOI: 10.5281/zenodo.21429405), and Path 4 (Karagöl Summit–Mount Elbrus, DOI: 10.5281/zenodo.21429686). Path 5: Cerro Champaquí → Aconcagua (483.5 km, 13 June 2023) On 13 June 2023, Roberto Antezana photographed Aconcagua — South America's highest peak — from Cerro Champaquí, Córdoba Province, Argentina, a 483.5 km line of sight that held the world record for longest photographed line of sight prior to the December 2024 Sağrak–Shkhara observation (Path 1 of this panel). This path is intentionally retained as a wide-margin ("comfortable") validation case, alongside Path 4: the observer–target elevation differential (4,170.8 m) is large enough that Aconcagua's summit is geometrically visible even at κ=0, with no atmospheric refraction at all. It is included to demonstrate that the method correctly predicts visibility across the full range of margin conditions, not only in near-threshold cases. Observer: Cerro Champaquí, Sierras de Córdoba, Argentina (31.983°S, 64.933°W, 2,790 m). Target: Aconcagua, north/main summit (32.65306°S, 70.01167°W, 6,960.8 m). Great-circle distance: 483.5 km. Date/time: 2023-06-13, ~21:45 UTC (dusk/sunset). Result: κ = 0.1316, required κ = 0.0000 — clear, visible even with zero refraction. Contents One JSON file containing the full path definition, κ result, S3 backfill note, and provenance/verification notes; and a README documenting method and data source provenance. Method Identical to Paths 1–4: refractivity N = 77.6·P/T + 3.73×10⁵·e/T² (Smith–Weintraub approximation to ITU-R P.453-14); ordinary least-squares regression of N against geometric altitude over the observer–target slice; κ = −R_Earth·(dN/dz)·10⁻⁶, R_Earth = 6,371,000 m. Full method detail in the main manuscript, §3.2–3.5. Provenance and verification Unlike Path 4, this dataset was retrieved via a direct call to the KAPPA backend API rather than the arc.kappasuite.com frontend, computed using a Python port of the production client-side κ/required-κ logic, verified line-by-line against the deployed frontend source code. ERA5 L137 data for this date was not present in the operational archive at the time of this validation and was manually backfilled for all four synoptic hours prior to computation. The documented observational difficulty of this specific event — a failed attempt one month earlier, extreme cold, and the need for exceptional atmospheric clarity — is attributable to atmospheric transparency/haze conditions, which this refraction-coefficient methodology does not model, rather than to refractive geometry. Notes This deposit extends the multi-path validation panel begun with Paths 1–4. Along with Path 4, it provides the panel's wide-margin comparison cases, complementing the near-threshold Paths 1–3.