AAS 98-134

DETERMINATION OF CLOSE APPROACHES FOR EARTH-FIXED LAUNCH TRAJECTORIES

J. Woodburn - Analytical Graphics, Inc.

Abstract

This work focuses on the determination of close approaches just after launch for cases where the trajectory is known in the Earth-Fixed reference frame but uncertainty exists in the time of launch. An algorithm is presented to determine all possible close approaches based on a launch time contained anywhere within a specified launch window in a single run. The corresponding blackout times during the launch window are also computed. This new algorithm requires substantially less computation time and is more robust than the simple technique of computing close approaches based on sampling throughout the launch window.

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