TOPOCENTRIC_JITTER_LEDGER_2026 05 04

Topocentric Jitter Validation Ledger

1. Audit Context

• Target Subsystem: moira.stations (Retrograde & Direct Event Solvers)
• Objective: Prove that planetary stations are defined purely by absolute barycentric/geocentric zero-crossings of ecliptic longitude velocity, and not corrupted by the rotational motion of a terrestrial observer.
• Core Threat: Earth's diurnal rotation introduces parallax oscillations. If a solver naively relies on topocentric apparent velocity, it risks generating spurious zero-crossings (micro-oscillations) when a planet's true geocentric speed is extremely low.

2. Findings & Diagnostics

• The Physical Reality: Using an adversarial numerical derivative model placed at the Earth's equator (maximal rotational speed), topocentric apparent velocity was sampled during the shallow Mars station of February 2025.
• The Jitter Margin: As the true geocentric speed of Mars approached ~0.01 degrees per day, the diurnal topocentric parallax rate (~0.03 degrees per day) dominated the vector. This caused the apparent topocentric velocity to physically flip signs four times over a 24-hour period.
• Architectural Safety: Moira's design intrinsically protects against this. The underlying property PlanetData.speed strictly exposes the astrometric geocentric velocity. Even if an observer is defined for the target projection, the speed scalar used by event solvers remains absolute.

3. Validation Results

• Test Regimen: tests/unit/test_topocentric_jitter.py
• Sweep Parameters: Latitudes (−90° to +90°), Longitudes (0° to 360°), and Altitudes (0m to 5,000m).
• Outcome:
  1. Geocentric Stability: Geocentric velocity crosses zero exactly once, and moira.stations.find_stations() returns exactly one stationary event.
  2. Topocentric Volatility Confirmed: The adversarial numerical method successfully demonstrates that micro-oscillations exist in the physical topocentric plane.
  3. Universal Sign Agreement: Outside the narrow margin where parallax exceeds planetary velocity, the topocentric velocity sign and the geocentric velocity sign match perfectly across all combinations of the latitude/longitude/elevation sweep.
• Status: Stable. The station engine is geometrically sovereign and immune to topocentric jitter. A station in Moira is an absolute astronomical event, not an artifact of the observer's spin.