WIND Nominal Mission Performance and Extended Mission Design

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WIND Nominal Mission Performance and Extended Mission Design

Franz, Heather / Sharer, Peter / Ogilvie, Keith / Desch, Mike

On November 1, 1994, the National Aeronautics and Space Administration launched the Interplanetary Physics Laboratory, or WIND spacecraft, as part of the Global Geospace Science program on a three-year mission to monitor the solar wind upstream of the Earth. The baseline mission design included a two-year dayside double lunar swingby orbit, followed by one year in a small-amplitude halo orbit at the Sun-Earth interior libration point, L₁. During operations, the double lunar swingby phase was expanded to three years. Execution of WIND’s seventeenth successful lunar flyby in October 1997, sending the spacecraft into an eight-month “halo orbit” loop of the double lunar swingby, marked the completion of the nominal mission phase and the inauguration of the extended mission. The extended mission design, which continues to evolve, has comprised various orbital phases and concepts, including the backflip, nightside double lunar swingby, deep-tail excursion, lunar orbit, high-inclination “petal” orbit, and Earth return trajectory, in the pursuit of new science objectives. This paper provides an overview of the original mission design and describes the evolution of both nominal and extended mission phases during WIND’s operational lifetime. The powerful mission design techniques that allowed accomplishment of a successful mission are discussed. Some of these techniques were first validated during flight of the International Sun Earth Explorer-3 (ISEE-3), while others constitute a novel approach to mission design implementation. Finally, WIND’s performance is summarized from both mission design and science perspectives.