The effort to free NASA's Spirit rover, currently mired in
sand on Mars, will begin in earnest today, when engineers team send the first escape
commands to the stuck robot to try to move out of its trap late tonight.
Spirit has been stuck in the Martian dirt since April, when drove
into a spot of soft terrain called "Troy" back in April.
Mission managers have spent the past six months devising
strategies to move the rover out of the sand pit. They tested them with
model rovers back on Earth that are essentially replicas of Spirit and
its twin, Opportunity.
Rover drivers decided that the best strategy would be to
have Spirit backtrack, moving forward to retrace the tracks that brought it
into its current predicament. (The rover's broken right front wheel has meant
that Spirit's primary mode of driving is backwards.)
NASA announced
the strategy last week, and the rover team plans to write the commands for
Spirit to drive out of Troy today and send them up to the rover in the wee
hours of Tuesday morning.
The results of the drive are expected to come back sometime
on Tuesday, after which the team will spend at least a day analyzing them
before sending up any more commands.
The precarious nature of the embedding — Spirit's wheels are
dug in to their hubs, one wheel has stopped spinning and a rock is sitting
underneath the rover's belly, possibly even touching it — means that the team
has to be very careful about any movements they make with the rover.
"This is by far the most complicated and complex"
embedding the team has had, said John Callas, project manager for the Mars
Exploration Rovers (MER) at NASA's Jet Propulsion Laboratory in Pasadena,
Calif.
Callas said the team expects any motion the rover makes to
be small at first and the process to take several weeks.
If Spirit has not yet been freed by the time or the rovers'
annual review rolls around in February, NASA officials will weigh whether to
keep trying, to keep Spirit where it is and continue doing science there or to
call it quits.
The team is upfront about the chances of getting Spirit out.
Ray Arvidson, deputy principal investigator for the rovers (and based at Washington University in St. Louis) has told fans of Spirit to be "hopeful, but
realistic."
And whether or not Spirit makes it out, NASA considers the
mission an unqualified success, as both MER rovers have last 24 times as long
as initially planned, as they come close to rounding out their sixth year on
the red planet.
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