|
Asteroid sample return mission MUSES-C (Hayabusa) |
|
Hayabusa
arrived in proximity of Itokawa on September 12th 2005,
and performed a detailed observation of the asteroid, including a global mapping. A candidate area for the two touch downs has been
defined on November 1st 2005. The first candidate for the touch
down has been identified in the area named MUSES-Sea (point A in the left figure
below). The second point candidate for the touch down has been identified in
the area named “Woomera
Desert” (point B in the right figure below)
（These pictures are from the JAXA press release） On November 9th Hayabusa
approached within 70 meters of the asteroid, and it took closer pictures of
the two prospective touch down areas. In the below pictures is shown on the
left a closer view of “MUSES-Sea” area, and on the right a closer
view of “Woomera Desert”
area.
（These pictures are from JAXA press
release, in Japanese） From these pictures it is possible to see clearly
rocks formation (boulders) of several meters in size (the red line on the right
corner in the above left picture represents a distance of 10 meters). These
rocks can be a major obstacles during the touch down and successive ascent
phase, thus here we show the results from numerical simulations for two cases
where extreme conditions have been considered.
During the development stage, experimental verifications have been conducted
on the sampler horn supposing that the surface around the contact area has a
30 degrees maximum inclination. The effects of a larger inclination have been
analyzed through numerical simulations, using different descending velocities
and different surface coefficients of friction. In both of the previous animations the
inclination of the surface in the contact area exceeds 50 degrees, but the
flexible horn worked correctly to effectively compensate for such surface
inclination. Another critical situation is represented
by the possibility that some parts of Hayabusa other than the horn
come in contact with the surface during the descending maneuver. This can happen
if there is a significant difference in height between the surface in the
contact area and the surface around it. In particular, it can be critical if
a part of the left and right solar paddles, each one measuring approximately
4.2m x 1.4m, is damaged, since it will be used to generate the electric power
needed by the ion engine used to take Hayabusa back to the earth. To avoid this problem, Hayabusa is
equipped with a Fan Beam Sensor (FBS). The sensor has the scope to scan the
area under the two solar paddles to detect any obstacle. If an obstacle is
detected, the four thrusters under the probe main body are fired, and the
descending operation is aborted. The below animation shows an example of
aborted touch-down due to the FBS obstacle detection. As possible to see,
such a situation can arise for example if Hayabusa ends up descending
in a gorge-like surface. Even if the touch down spot is relatively smooth
like in “MUSESC-Sea” area, still there is the possibility of damage caused by an high
isolated rock, and the FBS will be useful.
(clicking on the picture will start the movie). Available movies from Part 3 (November
2005) · Touch
down on a large inclined surface, case A (MPEG, 2.8M) · Touch
down on a large inclined surface, case B (MPEG, 2.8M) · Aborted
touch down due to FBS obstacle detection (MPEG, 2.8M)
· Touch
down on a smooth surface, example A (MPEG, 2.8M) · Touch
down on a smooth surface, example B (MPEG, 2.8M) · Touch
down on a rough surface, example A (MPEG, 2.8M) · Touch
down on a rough surface, example B (MPEG, 2.8M)
· MUSES-C
hovering on the asteroid surface (MPEG, 2.3M) · The
sampling collection procedure in slow motion (MPEG, 1.9M) · Complete
example of touch-down (MPEG, 2.3M)
The presentation
here is our outreach effort of research activities carried out with
responsibility of Space
Robotics Lab at Images and
animations in this page can be freely used. But please acknowledge to Dr. Yoshida when
used in news or publication medias. If you want an high definition version of
the animations (avi), please contact here. Space Robotics Lab at
Tohoku University Main
research topics (in English)
|
