PASADENA, Calif. -- NASA's Spirit rover has been on Mars for more than a week but still hasn't landed.
Instead, the six-wheeled vehicle sits parked 16 inches above the dirt and rocks of a planet it traveled 300 million miles to explore. Its wheels have yet to touch down on the surface.
The sequence of maneuvers needed to get the rover to roll into action has taken longer and proved more complex than expected. And the air bags that cushioned the rover's landing on Mars have been obstructing the vehicle's path, despite repeated efforts to pull them back.
As a result, the rover will probably not set its wheels down on the martian soil until Wednesday or Thursday, at least 12 days after its arrival on Mars. That is a week longer than NASA anticipated at launch.
The delays have caused much teeth-gnashing among mission members.
"The timing is a sign of the complexity and the complexity is the concern," said Richard Cook, deputy project manager of the $820 million double rover mission.
The scientists on the project are eager for Spirit to begin exploring Mars for signs that it was once wetter and more hospitable to life. But the engineers worry about the rover becoming stuck, toppling or otherwise damaging itself, perhaps fatally. Both groups want Spirit rolling on Mars before its identical twin, Opportunity, arrives Jan. 24.
For now, Spirit remains atop the opened petals of the lander that delivered it to the Red Planet
When Spirit bounced onto the surface of Mars on Jan. 3, NASA thought it would take a week for Spirit to unfold, photograph its surroundings and make some cursory scientific measurements before trundling off. But the process has gone more slowly than expected.
Further delaying Spirit's departure were two sections of the air bags blocking the ramp straight ahead of Spirit. NASA has been forced to plot a secondary and more risky route for the rover to use. That will require the rover to pirouette 115 degrees to its right.
Spirit's first steps should take 75 seconds to complete. It is a maneuver engineers have simulated more than 500 times on Earth.
"In all likelihood, it will be our most dramatic move," said Kevin Burke, a mechanical systems engineer on the mission,
The only previous rolling robot that the National Aeronautics and Space Administration sent to Mars was a simple affair. The microwave oven-sized Sojourner stood up, raised its antenna and shoved off just a day after its July 4, 1997, arrival on Mars aboard the Pathfinder spacecraft.
The golf cart-size Spirit is the robotic equivalent of the Sojourner rover and the Pathfinder lander rolled into one. There's nothing simple or fast about getting it ready.
"People want to know why it's taking so long. Well, it's a lot more complicated," said Rob Manning, who oversees the entry, descent and landing portion of the mission for NASA's Jet Propulsion Laboratory.
NASA had to fold, origami-like, the boxy rover to fit it into its pyramid-shaped lander. Just about everything that sticks out from the rover's foil-covered body had to be tightly stowed, including its solar arrays, camera mast, high-gain antenna, wheels, suspension and robotic arm.
"It boils down to putting a square peg in a round hole," mission manager Jennifer Trosper said.
Reversing the process takes time.
Chris Voorhees, a mechanical systems engineer on the mission, called it one of the most complex sequences ever performed on a robotic spacecraft.
Just getting Spirit to stand up from the crouched position it held during the seven months since launch required 12 pyrotechnic devices, nine motors, six latches and four sets of hazard-avoidance camera images - plus numerous sensors to monitor the entire orchestration, Voorhees said.
NASA hopes the design will also work for Opportunity. After that, the space agency probably will drop the landing scheme altogether for rover missions now on the drawing board.
"Certainly, it's more complicated than you'd like it to be," Trosper said.
For now, NASA officials continue to counsel patience with Spirit.
"You have this expensive asset on the surface of Mars. If you don't get it off on day 10, it's not the end of the world," said Firouz Naderi, manager of the Mars exploration program at JPL. "You have to take your time."
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