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ZL2VAL > ROVERS 07.05.05 13:26l 108 Lines 5621 Bytes #999 (0) @ WW
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Subj: Press release, 6th May
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Sent: 050507/1010Z @:ZL2AB.#46.NZL.OC #:61642 [New Plymouth] FBB7.00g
From: ZL2VAL@ZL2AB.#46.NZL.OC
To : ROVERS@WW
NEWS RELEASE: 2005-072
May 06, 2005
Rover Team Tests Mars Moves on Earth
Mars rover engineers are using a testing laboratory to simulate specific
Mars surface conditions where NASA's rover Opportunity has spun its
wheels in a small dune. Careful testing is preceding any commands for
Opportunity to resume moving to get out of the dune and continue exploring.
The rover team at NASA's Jet Propulsion Laboratory, Pasadena, Calif.,
has cooked up recipes combining various sandy and powdery materials for
the best simulation on Earth of the dune where Opportunity dug itself in
to wheel-hub depth last week. The team has not asked Opportunity to turn
its wheels at all since the rover bogged down during a drive on April 26.
"We choose to proceed cautiously, so we don't expect to begin actually
driving out of the dune before next week, possibly later," said Jim
Erickson, rover project manager at JPL. "Both Opportunity and Spirit
have already provided many more months of scientific exploration than
anyone expected. By taking good care of them, we hope to keep them
exploring for more months to come. Tests so far have sustained our
optimism about Opportunity's ability to drive out of this dune, but we
have more testing ahead to understand how robust that capability is."
Opportunity had driven about 40 meters (131 feet) of a planned 90-meter
(295-foot) drive on the rover's 446th martian day when its wheels began
slipping. The rover was driving backwards at the time. The team
frequently alternates between backwards and forwards driving to keep
wheel lubrication well distributed. The wheels kept rotating enough
times to have covered the rest of the distance if they hadn't been
slipping, but the rover eventually barely inched forward. After a turn
at the end of the planned drive, Opportunity sensed that it had not
turned properly and stopped moving.
Opportunity is positioned across the ridge of an elongated dune or
ripple of soft sand that is about one-third meter (one foot) tall and
2.5 meters (8 feet) wide. "We've climbed over dozens of ripples, but
this one is different in that it seems to be a little taller and to have
a steeper slope, about 15 degrees on part of its face," said Mark
Maimone, a JPL rover mobility engineer.
Last week, engineers arranged a simulated dune using sand that was
already at JPL's rover testing facility and put a test rover into a
comparably dug-in position. The test rover had no difficulty driving
away, even when sunk in belly-deep. However, that sand offered better
traction than the finer, looser material that appears to make up the
surface at Opportunity's current position. "We needed to do tests using
material more like what Opportunity is in, something that has a fluffier
texture and cakes onto the wheels," said JPL rover engineer Rick Welch,
who is leading the tests.
Experimenting with different mixtures, engineers and scientists came up
with a recipe that includes play sand for children's sandboxes,
diatomaceous earth for swimming pool filters and mortar clay powder.
Then they went to several home supply and hardware stores to find enough
bags and boxes of the ingredients to make more than 2 tons of the
simulated Mars sand for more realistic mobility tests, said JPL rover
mobility engineer Jeff Biesiadecki.
Dr. Robert Sullivan of Cornell University, Ithaca, N.Y., a rover science
team member, worked with engineers in the JPL testbed to match the
properties of the test sand as closely as possible with those of the
sand beneath Opportunity, based on images of wheels and wheel tracks on
Mars. "We found that when the wheels dig in, the material we're using
does stick to the wheels and fills the gaps between the cleats, but it
doesn't stick when you're just driving over it. That's good because it's
the same as what we see in the images from Opportunity," Sullivan said.
Experiments indicate that in this more powdery material, the test rover
positioned comparably to Opportunity can drive out after some initial
wheel-spinning. More testing, analysis, planning and review will precede
any actual commands for Opportunity to begin driving away from the dune.
Meanwhile, Opportunity has been using its cameras to study its
surroundings at the edge of a region called "Etched Terrain." Since
landing more than 15 months ago, it has driven 5.35 kilometers (3.32
miles). Spirit, halfway around Mars, has recently been using all of its
research tools to examine an outcrop called "Methuselah," the first
outcrop of layered rock that Spirit has found. The rover has also been
taking short movies of dust-carrying whirlwinds called "dust devils." On
some afternoons, the rover sees several at once moving across the plain.
Spirit has driven a total of 4.31 kilometers (2.68 miles).
JPL, a division of the California Institute of Technology in Pasadena,
has managed NASA's Mars Exploration Rover project since it began in
2000. Images and additional information about the rovers and their
discoveries are available on the Internet at:
http://www.nasa.gov/vision/universe/solarsystem/mer_main.html
and: http://marsrovers.jpl.nasa.gov
-=###=-
73, Alan
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