Station Keeping History of Hayabusa at Itokawa
- From: baalke@xxxxxxxxxxxxx
- Date: 29 Sep 2005 08:57:05 -0700
http://www.isas.ac.jp/e/snews/2005/0929.shtml
Station Keeping History of Hayabusa to Itokawa
JAXA
September 29, 2005
Hayabusa arrived at what we call the Gate Position, about 20 km from
Itokawa on September 12th. Since then to 21st, Hayabusa had kept the
relative position control (Station Keeping) via the Optical Hybrid
Navigation. A three dimensional view of the trajectory as well as its
time history are shown below.
The coordinate used here is, so called, HP (Home Position) frame, in
which the Z axis is taken to the Earth direction and Y-axis is
southward
in ecliptic frame and normal to the plane that is spanned by
Sun-to-Itokawa and Sun-to-Earth lines and X-axis should constitute the
right-hand coordinate. The station keeping maneuver maintains its
altitude (Z-position) at the same time controls the Itokawa direction
at
the center in X-Y plane. The control box defined is a little loosened
so
that the number of corrections can be minimized. Note even 1 cm/second
velocity residual leads to the drift of up to 1 km per day, and this
station keeping is performed very carefully.
As the following figures indicate, the station keeping has been carried
out satisfactorily. Next week, Hayabusa lowers its altitude to the Home
Position, where this task will be much harder due to the high
sensitivity. The operation team will continue making an intensive
effort
to accomplish the proximity observation.
HP Coordinate Station Keeping History
[Station Keeping Time History]
[Station Keeping at a glance]
The figure shows the station keeping locus
at a glace including Itokawa. Here, the size of Itokawa is not in
scale.
This tells how accurately the spacecraft position has been controlled.
The next web report will introduce how Hayabusa lowers its altitude and
reach the Home Position.
.
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