The dynamics of orbit uncertainty in an unstable orbital environment are discussed

with specific application to the orbit determination of a halo orbit about

the Earth{Sun L1 point. This article documents a simplified orbit determination

covariance program developed under Telecommunications and Mission Operations

Division Technology support. The program is ideally suited to investigate spacecraft

trajectory navigation in challenging environments, where the basic dynamics

of the trajectory can no longer be modeled using near-Keplerian motion.