Mars rover approaches heat shield
Hardware was cast off last January as part of rover's landing system
By Leonard David
SPACE.com
(SPACE.com) -- The Opportunity Mars rover has turned into a junkyard dog, prowling ever closer to a hunk of space litter at Meridiani Planum -- a discarded heat shield.
During its January 25 plunge toward the red planet, the Opportunity rover was encapsulated in a protective aeroshell comprised of two key parts: a heat shield and a backshell that contained essential landing gear.
After taking the brunt of atmospheric friction, the heat shield was jettisoned high above Mars. The hardware fell several miles before hitting the Meridiani Planum landscape at a smashing speed.
Double bonus
Fresh from exploring the remarkable Endurance Crater, the Opportunity rover is now rolling toward the beat up heat shield that's been sitting on Mars for nearly 11 months.
Steve Squyres, principal investigator for the Mars Exploration Rover effort, said the Opportunity assessment of the heat shield offers a double-bonus.
"For the scientists, it may be a chance to look at the deepest fresh hole in the ground that we'll ever see on Mars." said Squyres of Cornell University. "For the engineers, it's an unprecedented chance to see how a heat shield performed during entry through the martian atmosphere. There's something for everybody."
As the robot wheels across the martian plain that is Meridiani Planum, its panoramic camera has begun snapping clearer and clearer images of the distant heat shield. The Pancam is a high-resolution color stereo pair of CCD cameras located on a camera bar that sits on top of the mast of the rover.
Furthermore, there is discussion about making more than a drive-by camera shooting of the refuse -- perhaps using the robot's microscopic imager (MI) to examine the spent heat shield up-close and personal.
"We'll definitely do a lot of careful imaging with Pancam. We will use the MI only if we find that it's safe and productive to do so. Stay tuned," Squyres added.
Entry and impact
There's good science ahead, said Ray Arvidson, an Earth and planetary sciences expert at Washington University in St. Louis, Missouri, and deputy principal investigator for the Mars Exploration Rover instruments.
"The heat shield campaign is focused on an inventory of the heat shield and its components, including analyses of what happened during entry and impact," he said.
Arvidson said that along the way and next to the shield, Opportunity scientists will be conducting observations aimed at understanding the mechanical properties of the surface, based on excavations during the impact.
"We are also interested in looking at the soils and rocks exposed during impact and making imaging and other measurements of these materials. This latter set of experiments will allow us to probe subsurface characteristics," Arvidson explained.
First-ever inspection
Spacecraft engineers are keen on making the first-ever inspection of a heat shield that penetrated Mars' atmosphere.
Lockheed Martin Space Systems in Denver, Colorado designed and built the Mars Exploration Rover aeroshell structure and thermal protection system.
The blunt-nosed cone of a heat shield was covered with a layer of phenolic honeycomb. A phenolic compound is made from benzene and is typically used in various plastics, disinfectants, and pharmaceuticals. This phenolic honeycomb is filled with an ablative material -- also called an ablator -- which dissipates heat generated by atmospheric friction.
The ablator itself is a unique blend of cork wood, binder and many tiny silica glass spheres. The heat shield has a thick, one-half inch (12.7 millimeter) layer of the ablator.
Images taken by Opportunity might reveal how well the protective shield withstood the atmospheric fireworks it encountered in slicing through Mars' atmosphere, as well as yield data leading to better heat shield designs.
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