Analysis Of Artemis Ii Flight-Derived Ephemeris Planar Geocentric Operational Baseline With Post-Measurement Geoid And Spherical Corrections

Abstract

The official flight-derived ephemeris for Artemis II (NASA BET product, April 10, 2026) is examined after systematic removal of all post-measurement spherical, geoid, and rotational corrections. When these terms are stripped, the resulting dataset collapses to a short-duration ballistic parabolic arc on a stationary planar geocentric baseline with local uniform gravity. Curvature drop remains below 1 m, velocity components reduce to north-down/east-down planes, and the final splashdown velocity matches the engineered 17-20 mph value under the simple gravity-pendulum model employed by the parachute pendulosity observers. This analysis confirms that raw sensor measurements, inertial navigation, and descent control algorithms operated entirely on a planar geocentric reference frame, with spherical corrections applied exclusively during Best Estimated Trajectory (BET) reconstruction via Kalman filtering. The raw engineering reality of Artemis II is therefore consistent with a stationary planar geocentric Earth.