January 13, 2004
Spirit's
Travel Plans: See Crater, Head for Hills
NASA scientists are currently planning
to have the Mars Exploration Rover Spirit investigate a nearby
crater before sending it off to the horizon to see if it can
reach the closest set of hills.
Rover's Location Found by
Identifying Hills on Overhead Images
Click
for larger image
Courtesy NASA/JPL/MSSSS
Determining where the spacecraft landed
by using images taken from orbit has given planners a useful
map of the vicinity. After Spirit drives off its lander and examines
nearby soil and rocks, the scientists and engineers managing
it from NASA's Jet Propulsion Laboratory, Pasadena, Calif., intend
to tell it to head for a crater that is about 250 meters (about
270 yards) northeast of the lander.
"We'll be careful as we approach.
No one has ever driven up to a martian crater before," Dr.
Steve Squyres of Cornell University, Ithaca, N.Y., principal
investigator for the science instruments on Mars Exploration
Rovers, said.
The impact that dug the crater about 200
meters (about 220 yards)wide probably flung rocks from as deep
as 20 to 30 meters (22 to 33 yards) onto the surrounding surface,
where Spirit may find them and examine them. "It will provide
a window into the subsurface of Mars," Squyres said.
Craters come in all sizes. The main scientific
goal for Spirit is to determine whether the Connecticut-sized
Gusev Crater ever contained a lake. Taking advantage of the nearby
unnamed crater for access to buried deposits will add to what
Spirit can learn from surface materials near the lander.
After that, if all goes well, the rover
will head toward a range of hills about 3 kilometers (2 miles)
away for a look at rocks that sit higher than the landing neighborhood's
surface. That distance is about five times as far as NASA's mission-success
criteria for how far either rover would drive. The highest hills
in the group rise about 100 meters (110 yards) above the plain.
The Hills in the East, Labeled
as in the Map Above, as Seen from the Rover.
Click
for larger image
Courtesy NASA/JPL/MSSS
"I cannot tell you we're going to
reach those hills," Squyres said. "We're going to go
toward them." Getting closer would improve the detail resolved
by Spirit's panoramic camera and by the infrared instrument used
for identifying minerals from a distance.
First, though, comes drive-off. Overnight
Monday to Tuesday, Spirit began rolling. It backed up 25 centimeters
(10 inches), turned its wheels and pivoted 45 degrees.
"The engineering team is just elated
that we're driving," JPL's Chris Lewicki, flight director,
said. "We've cut loose our ties and we're ready to rove."
After two more pivots, for a total clockwise turn of 115 degrees,
Spirit will be ready for driving onto the martian surface very
early Thursday morning, according to latest plans.
Engineers and scientists have determined
where on the martian surface the lander came to rest. NASA's
Mars Odyssey orbiter was used in a technique similar to satellite-based
global positioning systems on Earth to estimate the location
of the landing site, said JPL's Joe Guinn of the rover mission's
navigation team. Other researchers correlated features seen on
the horizon in Spirit's panoramic views with hills and craters
identifiable in images taken by Mars Global Surveyor and Odyssey.
"We've got a tremendous vista here with all kinds of features
on the horizon," JPL's Dr. Tim Parker, landing site-mapping
geologist, said.
The spacecraft came to rest only about
250 to 300 meters (270 to 330 yards) southeast of its first impact.
Transverse rockets successful slowed horizontal motion seconds
before impact, according to JPL's Rob Manning, who headed development
of the entry, descent and landing system. The spacecraft, encased
in airbags, was just 8.5 meters (27.9 feet) off the ground when
its bridle was cut for the final freefall to the surface. It
first bounced about 8.4 meters (27.6 feet) high, then bounced
27 more times before stopping.
Analysis of Spirit's landing may aid in
minor adjustments for Opportunity, on track for landing on the
opposite side of Mars on Jan. 25 (Universal Time and EST; 9:05
p.m. Jan. 24, PST).
JPL, a division of the California Institute
of Technology in Pasadena, manages the Mars Exploration Rover
project for NASA's Office of Space Science, Washington.
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