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 |
 |
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."
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.
|
