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Robotic Rockhounds: Twin Mars Rovers to Use High-Tech Tools By Tariq Malik Staff Writer posted: 07:00 am ET 16 April 2003 |
The first geologists on Mars are not going to be humans of flesh and bone, but robot automatons of metal and wheels.
This summer, NASA plans to launch the Mars Exploration Rovers mission (MER), sending a pair of robotic twins into space. If all goes well, the six-wheeled rovers will be rolling around the Red Planet sometime in January 2003.
While there are some similarities to Mars Pathfinder, NASA's 1997 lander that deployed the small Sojourner rover, the MER mission is far from a mere echo of planetary probes gone by. With a total of nine cameras, a sophisticated set of instruments and a human-sized robot arm, each rover will serve as a geologist proxy, seeking out any indications of water -- past or present -- on Mars.
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"The Pathfinder mission was just what it sounds like, a pathfinder," said Cornell professor Steven Squyres, principal investigator for the rover mission's science payload, during a telephone interview. "It proved the key technology to get to Mars and land."
Getting there with what works
Like Pathfinder, both MER rovers will be delivered to Mars by rocket and use an aeroshell to deflect heat as they punch their way through the Martian atmosphere. A parachute will slow each lander, with the folded-up rover nestled inside, until an airbag envelope inflates and the craft makes a bouncy landing on the Martian surface.
It's a tried and true method of dropping something on Mars.
"[The lander] will basically slam into the Martian atmosphere like a bullet," said Rob Manning, MER manager of Entry, Descent and Landing Operations at NASA's Jet Propulsion Laboratory (JPL). Manning also oversees MER systems engineering for the project and served on the 1997 mission as well. "It's entry and descent is based in entirety on its Mars Pathfinder cousin."
But, Manning told SPACE.com, despite their similarities, each MER probe landing procedure does have some advancement over its predecessor, including more motors and gears than Pathfinder ever needed.
Once the airbags deflate and the lander petals open, the rover will unfurl its solar array and raise its mast, as the front two wheels fold out from their stowed position. The MER rover will then abandon its landing shell like a butterfly leaving its chrysalis and begin exploring the Martian surface.
A geologist's proxy
Each MER rover carries the Athena science package, a cluster of scientific instruments that researchers hope will paint a comprehensive climate history on Mars, while looking for signs of water.
"What we tried to do was take everything you'd find in a field geologist's toolkit on Earth and make a robotic field geologist for Mars," Squyres said.
Sitting atop the rover mast is Pancam, the most powerful color imaging system ever to land on another world. The camera system will return high-definition views of Mars, and serve as the surveying tool for MER researchers in deciding where to send the robot. A filter wheel on each of Pancam's two cameras allows observations in multiple spectrums. Next to Pancam on the mast is the Miniature Thermal Emissions Spectrometer (Mini-TES), the first of three infrared spectrometers aboard each rover that will work in tandem with the Pancam to determine suitable target rocks and soil for study.
Reach out and touch rock bottom
Each rover also has an arm similar in size and movement to that of a human adult, with three flexible joints and a cluster of instruments at the end. Among them are the Mössbauer and Alpha X-Ray spectrometers, which will look for iron-bearing formations that could have been shaped by once-running water and determine their mineral composition, respectively.
Also at on the tip of the arm is the tiny Microscopic Imager (MI), a combination between a microscope and black-and-white CCD camera that will provide detailed images of some of Mars' tiniest features.
"The Mössbauer and the MI are instruments so different than anything we've ever sent to Mars," Squyres said. "We're going to try and put that arm into action rather quickly."
To peek deeper into the Red Planet's geologic past, each MER robot is equipped with a Rock Abrasion Tool -- or RAT -- capable of grinding a hole 2 inches (45 millimeters) wide and 5 millimeters deep into any rock within reach. By scraping away even millimeters of the rock's surface, researchers can use other instruments to study material undisturbed by the harsh Martian weather.
Finally, an array of magnets built into the rover's deck, arm and undercarriage will attract Martian dust and other small particles that could provide freeze-dried evidence of water.
But MER researchers stressed that the Athena package works best as an ensemble, with no one instrument dominating the pack. "I love all my children equally," Squyres said of the MER instruments.
Roving about Mars
The MER rovers are not quick robots. While scientists expect them to traverse 330 feet (100 kilometers) each of their 90 days on Mars, they typically move about 2 inches (5 centimeters) per second. The limitation is set not so much by the rotation speed of its wheels as by the amount of data each robot must analyze before making a move.
A pair of navigation cameras sit up top on the robot's mast, while four hazard cameras, two front and two aft, consistently record images of the terrain around each rover. Each time a MER robot moves, the hazard cameras take more images, feed them into the onboard computer which analyzes them to decide whether an obstacle can be surmounted or avoided. If it gets in a real jam, then it phone's home for instructions. Both rovers will be in contact with Earth via NASA's Deep Space Network and be able to relay data through the Mars Odyssey spacecraft, currently in orbit around the planet.
"The rule is, 'Don't go over anything larger than your wheel,'" Squyres said. The wheels on each of the 400-pound (180-kilogram) rovers stand about 10 inches (25 centimeters) tall.
But MER scientists will also be able to tailor the hazard level up or down depending on Martian terrain each robot faces. "So if we land in a parking lot, and think the terrain is relatively safe, then we'll give the rover a longer leash," Manning said, adding that rover controllers can also set waypoints for each MER robot to pause and reevaluate its surroundings before moving on.
Manning added that the challenge is to get the most science out of each day on Mars. The MER robots will typically be in "sleep" mode for up to 18 hours each Martian night, but some experiments will be conducted in darkness. After 90 days, researchers expect dust build-up on the MER solar arrays to impact the rover's power supply and ability to conduct experiments.
First you have to get there
The original launch date for the first MER mission, MER-A, was set for May 30. But this week NASA rescheduled the launch for no earlier than June 6, after a
problem was detected with the cables that connect the rover's main computer with the cruise stage that will ferry it to Mars. Engineers will have to make the necessary adjustments before MER-A can launch, though the setback should not affect the second rover mission expected to liftoff between June 25 and July 15."Right now we just want to make sure we have everything worked out, and there's some cushion built into our [launch] schedule," Manning said. "But it's going to be an exciting mission once we get there. "
