Mars Rovers Head For Exciting Landings In January

Donald Savage
Headquarters, Washington               December 2, 2003
(Phone: 202/358-1547)

Guy Webster
Jet Propulsion Laboratory, Pasadena, Calif.
(Phone: 818/354-6278)

RELEASE: 03-387

MARS ROVERS HEAD FOR EXCITING LANDINGS IN JANUARY

     NASA'S robotic Mars geologist, Spirit, embodying 
America's enthusiasm for exploration, must run a grueling 
gantlet of challenges before it can start examining the red 
planet. Spirit's twin Mars Exploration Rover, Opportunity, 
also faces tough Martian challenges.

"The risk is real, but so is the potential reward of using 
these advanced rovers to improve our understanding of how 
planets work," said Dr. Ed Weiler, associate administrator 
for space science at NASA Headquarters, Washington. 

Spirit is the first of two golf-cart-sized rovers headed for 
Mars landings in January. The rovers will seek evidence about 
whether the environment in two regions might once have been 
capable of supporting life. Engineers at NASA's Jet 
Propulsion Laboratory (JPL), Pasadena, Calif., have navigated 
Spirit to arrive during the evening of Jan. 3, 2004, in the 
Eastern time zone.

Spirit will land near the center of Gusev Crater, which may 
have once held a lake. Three weeks later, Opportunity will 
reach the Meridiani Planum, a region containing exposed 
deposits of a mineral that usually forms under watery 
conditions. 

"We've cleared two of the big hurdles, building both 
spacecraft and launching them," said JPL's Peter Theisinger, 
project manager for the Mars Exploration Rover Project. "Now 
we're coming up on a third, getting them safely onto the 
ground," he said.

Since their launches on June 10 and July 7 respectively, each 
rover has been flying tucked inside a folded-up lander. The 
lander is wrapped in deflated airbags, cocooned within a 
protective aeroshell and attached to a cruise stage that 
provides solar panels, antennas and steering for the 
approximately seven month journey. 

Spirit will cast off its cruise stage 15 minutes before 
hitting the top of the Martian atmosphere at 5,400 meters per 
second (12,000 miles per hour). Atmospheric friction during 
the next four minutes will heat part of the aeroshell to 
about 1,400 C (2,600 F) and slow the descent to about 430 
meters per second (960 mph). Less than two minutes before 
landing, the spacecraft will open its parachute.

Twenty seconds later, it will jettison the bottom half of its 
aeroshell, exposing the lander. The top half of the shell, 
still riding the parachute, will lower the lander on a 
tether. In the final six seconds, airbags will inflate, retro 
rockets on the upper shell will fire, and the tether will be 
cut about 15 meters (49 feet) above the ground. 

Several bounces and rolls could take the airbag-cushioned 
lander about a kilometer (0.6 mile) from where it initially 
lands. If any of the initial few bounces hits a big rock 
that's too sharp, or if the spacecraft doesn't complete each 
task at just the right point during the descent, the mission 
could be over. More than half of all the missions launched to 
Mars have failed. 

JPL Director Dr. Charles Elachi said, "We have done 
everything we know that could be humanly done to ensure 
success. We have conducted more testing and external reviews 
for the Mars Exploration Rovers than for any previous 
interplanetary mission."

Landing safely is the first step for three months of Mars 
exploration by each rover. Before rolling off its lander, 
each rover will spend a week or more unfolding itself, rising 
to full height, and scanning surroundings. Spirit and 
Opportunity each weigh about 17 times as much as the 
Sojourner rover of the 1997 Mars Pathfinder mission. They are 
big enough to roll right over obstacles nearly as tall as 
Sojourner.

"Think of Spirit and Opportunity as robotic field 
geologists," said Dr. Steve Squyres of Cornell University, 
Ithaca, N.Y., principal investigator for the rovers' 
identical sets of science instruments. "They look around with 
a stereo, color camera and with an infrared instrument that 
can classify rock types from a distance. They go to the rocks 
that seem most interesting. When they get to one, they reach 
out with a robotic arm that has a handful of tools, a 
microscope, two instruments for identifying what the rock is 
made of, and a grinder for getting to a fresh, unweathered 
surface inside the rock," he said.

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 information 
about the Mars Exploration Rover project on the Internet, 
visit:

http://mars.jpl.nasa.gov/mer 

For Cornell University's Web site about the science payload, 
visit:

http://athena.cornell.edu 

  -end-