[meteorite-list] NASA Plots Escape for Stranded Mars Rover

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon May 9 16:14:33 2005
Message-ID: <200505092013.j49KDw423510_at_zagami.jpl.nasa.gov>

http://www.newscientist.com/article.ns?id=dn7356

NASA plots escape for stranded Mars rover
Kelly Young
New Scientist
09 May 2005

NASA could take its first steps to rescue its Opportunity rover from a
Martian sand dune on Monday.

On 25 April, the ground control team at NASA's Jet Propulsion Laboratory
in Pasadena, California, US, woke up to find that Opportunity had not
progressed to the point they expected. Some of its wheels had dug
themselves into a sand dune, and were slipping.

Controllers immediately halted Opportunity and instructed it to take
pictures of its wheels. Its corner wheels were between halfway and
three-quarters buried. "That's not where we'd like them to be," says Jim
Erickson, the rovers' project manager.

Since then, Opportunity has used its instruments to try to determine
what exactly its wheels have dug into, while NASA scientists on Earth
have tried to simulate the Martian soil and the dunes.

They made 2 tonnes of Mars-like soil using fine clay, playground sand
and diatomaceous earth, which has the consistency of flour but consists
of fossilised shells of diatoms. Erickson explains that it is the
consistency of the material and not the fact that it contains tiny
skeletons that is important for their tests.

The team then drove two test rovers backwards and forwards through the
manmade dunes. "Everything we try works like a champ," Erickson told New
Scientist.
          
Freewheeling

NASA is playing it safe with its $400 million rover, which has roamed
over 5.3 kilometres of Martian landscape since it landed on 25 January 2004.

On Friday, an external review board looked at options for getting the
rover off the dune. They were expected to present their final report on
Monday. "They generally agreed with the approach that we're taking,"
Erickson says.

If everything continues to goes well, ground controllers will begin
developing the first escape commands to send to Opportunity on Monday.
The first step will be to straighten rover's wheels, but getting the
rover clear of the dune may take days, possibly even weeks.

To get the wheels out of the sand, mission managers will not spin the
rover's wheels quickly or rock it back and forth, like a car stuck in
the mud. The rover is too light for this to result in any traction for
the wheels. Instead, they plan to turn the wheels very slowly.
          
Soil-caked cleats

"The early steps in the extraction process don't look like much," writes
rover chief scientist Steve Squyres on his website. "Even though you're
making crucial progress, moving soil bit by bit beneath the wheels, the
rover itself hardly moves, sometimes for quite a while."

Several factors may have contributed to Opportunity's dilemma. Pictures
show that the soil has caked between the cleats on the rover's wheels,
which may have contributed to its loss of traction.

Other factors include the height of the dune on which Opportunity is
parked. It is 30 centimetres high, slightly taller than the dunes it had
previously climbed, which were between 20 and 25 centimetres. The
current dune is also steeper, with a 15? incline.

Opportunity could alternatively take a longer but more gradually sloping
route, or even take a complete detour around the dunes by travelling on
a rocky surface.
 
Received on Mon 09 May 2005 04:13:57 PM PDT