<h2>AAS 95-408</h2><h2>Mitigation of Orbit Errors Resulting from the Numerical Integration Across Shadow Boundaries</h2><h4>J. B. Lundberg, Auburn University, Auburn, AL</h4><h2> Abstract </h2>The long arc, precision orbit determination solutions for Lageos II indicate that the numerical integration errors introduced by the apparent force discontinuities when the boundary of the Earth's shadow is crossed are being aliased into the parameters used to model the Solar-Yarkovsky effect.  A model is proposed that predicts when this type of numerical integration error is amplified by a "resonance" caused by the selection of the numerical integration stepsize.  Various techniques for mitigating these errors are investigated including the method of modified back differences.<br><br>