Subject: Testing A Supplemental Earth Orientation Model
From: Daniel Adamo <[email-masked]>
To: "ATIG (L-Z)" <[email-masked]>
Date: Thu, 10 Aug 2023 21:59:51 -0700

ATIG Members-

The subject model computes rotation, nutation, and precession (RNP) dynamics transforming coordinates between an Earth-fixed system such as latitude/longitude/altitude and an inertial system such as the Earth mean equator and equinox of epoch J2000.0.  The Swift-based trajectory design/modeling system I’ve been developing since 2017 uses data files from JPL to provide precision Earth orientation transformations, but these highly accurate files do not support times before year 1972.  In accurately reconstructing Apollo Program trajectories, it is therefore necessary to perform precision RNP computations in Swift code.  The attached paper provides testing data demonstrating these computations are sufficiently accurate for Apollo trajectory reconstruction.  Your comments on this material are invited.

-Dan