WIND Nominal Mission Performance and Extended Mission Design
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WIND Nominal Mission Performance and Extended Mission Design 1 Heather Franz,' Peter Sharer,' Keith Ogilvie," and Mike Desch 4 Abstract 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, L 1. 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.
Introduction The Interplanetary Physics Laboratory (WIND), launched on November 1, 1994, is one of two spacecraft that comprise the National Aeronautics and Space Administration's (NASA) Global Geospace Science (GGS) program. Both WIND and fellow GGS spacecraft POLAR are elements of the International Solar Terrestrial Physics I An earlier version of this paper was presented at the AIAA/AAS Astrodynamics Specialist Conference, Boston, Massachusetts, August 1998. 2Senior Member of Technical Staff, Computer Sciences Corporation, NASA Goddard Space Flight Center, Greenbelt, MD 20771, e-mail: [email protected]. 3Ellicott City, Maryland, e-mail: [email protected]. 4 NASA Goddard Space Flight Center, Laboratory for Extraterrestrial Physics, Greenbelt, MD 20771.
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(ISTP) program, the goal of which is to understand the physical processes of the solar-terrestrial system. The cornerstone of WIND's nominal mission design is a dayside double lunar swingby (DLS) orbit, in which multiple lunar gravity assists alternately raise and lower the orbit apogee and maintain a Sun-synchronous apsidal rotation rate [1]. This trajectory has allowed WIND to monitor the solar wind upstream from the Earth, studying the interaction of the solar wind
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