Long-Life Europa Geodesy Orbits Accounting for Navigation Uncertainties

Abstract

This work investigates the properties of phase space near a periodic orbit and their applications to orbit design and orbit determination. A low-altitude, near-polar periodic orbit is computed and an error covariance is generated by processing range-rate and altimetry measurements over seven days. The resulting covariance is used to disperse the orbit initial conditions in a Monte Carlo simulation. The distribution of the Monte Carlo run is biased toward longer orbit lifetimes, due to the stable and unstable manifolds associated with the periodic orbit. The orbit determination covariance is mapped into manifold coordinates and long lifetime orbits are shown to be aligned with the stable manifold. Periodic orbit continuation is used to generate a family of orbits with similar phase-space characteristics to understand the variation of manifold structure with orbit elements and Jacobi energy. The effect of Europa eccentricity on the phase-space location of long lifetime orbits is discussed and conclusions are given regarding the connection between orbit lifetime, design, and determination.