Go To That Crater And Turn Right: Spirit Gets A Travel Itinerary
January 13, 2004
NASA's Spirit has begun pivoting atop its lander platform on Mars,
and the robot's human partners have announced plans to send it
toward a crater, then toward some hills, during the mission.
Determining exactly where the spacecraft landed, in the context of
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," said Dr. Steve Squyres of Cornell
University, Ithaca, N.Y., principal investigator for the science
instruments on Spirit and on its twin Mars Exploration Rover,
Opportunity.
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.
"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," said JPL's
Chris Lewicki, flight director. "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," said JPL's Dr. Tim
Parker, landing site-mapping geologist.
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, said 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. For more information about
NASA and the Mars mission on the Internet, visit
http://www.nasa.gov. Additional information about the rover
project is available from NASA's JPL at
http://marsrovers.jpl.nasa.gov and from Cornell University at
http://athena.cornell.edu.
