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  Halo (L1) Orbit Insertion

Genesis entered orbit around the L1 point on Nov. 16, 2001. At arrival, the spacecraft's large thrusters fired to put it into an elliptical, or looping, orbit around the L1 point. Genesis completed five orbits around L1; nearly 80 percent of the mission's total time was spent collecting ions from the Sun.

Genesis Planned Trajectory


  What is LOI?

Don Sweetnam
Don Sweetnam

According to Mission Project Manager Don Sweetnam, "LOI is a spacecraft maneuver that enables a transition from the launch and early portion of the mission to the science sample collection portion of the mission. This is a mission milestone because a successful LOI maneuver will put us into an orbit that ensures we can collect solar wind samples for two years and puts us on the proper trajectory to get back to Earth when sample collection is completed."

   When did LOI happen?

The Genesis spacecraft went into perfect orbit insertion about the first Lagrangian point, L1, the morning of November 16, 2001. According to Mission Design and Navigation Team Lead George Carlisle, "Every mission begins with the design of a trajectory. The resulting trajectory must meet the mission requirements, primarily those defined by the scientific goals of the mission. On Genesis, those goals are to collect charged particles from the solar wind and return them to Earth. The Genesis mission trajectory was chosen because it takes the spacecraft and science instruments to a point in space far enough removed from the geomagnetic field of Earth to permit collection of solar wind samples before they interact with that field. Because of the ability to linger near the Lagrangian Point (L1) for many months, it also allows sufficient time for the solar wind particles to accummulate within the sample collection arrays.

The recent LOI (Lissajous Orbit Insertion) maneuver, on November 16, set up the five halo loops that Genesis will complete around L1 (lasting about 30 months), thus beginning the science part of the mission. Though this was a modest maneuver, it made the difference between allowing us to stay near L1 and collect the valuable science data represented by the solar wind particles over the next two and a half years, and falling back to Earth within a few months, empty handed.

It's true that other missions have monitored solar wind in halo orbits, but we are the first mission to collect samples of solar wind and return them to the Earth for scientific analysis. This is what makes us unique among other halo orbit missions. Our daytime return to Earth in 2004 will truly be an exciting event."

The term stands for Lissajous Orbit Insertion (LOI). Lissajous lines are curved lines that form a figure 8 pattern. button
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Curator: Aimee Meyer
Updated: November 2009

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