A prototype of NASA's next generation of Martian rovers, nicknamed Rocky 7, has navigated successfully over a corner of Lavic Lake, an ancient lake bed about 275 kilometers (175 miles) east of Los Angeles, taking panoramic photographs and close-ups of the cratered terrain.
The three-day experiment, conducted Dec. 17-19 by a team of engineers at NASA's Jet Propulsion Laboratory and other institutions, was designed to demonstrate the rover's ability to drive a much greater distance than current rovers over rugged terrain reminiscent of Mars. The tests also demonstrated new mechanical innovations for 21st century rovers, such as a robotic arm that would be used to dig into soil and an agile mast that could be used to image the surrounding terrain and position miniature science instruments in tricky locations, said Dr. Samad Hayati, experiment engineer at JPL.
"The rover was very successful in making a long journey on its own, driving more than 200 meters (655 feet) to its target and relying on only specified location points along the way and information about the target," Hayati said. "Some of the key objectives of the next series of rovers will be their ability to navigate much greater distances autonomously and their ability to study the nooks and crannies on Mars where other robots were unable to go."
Robotic exploration of Mars over the next 10 years will focus on climate, the search for water and hints that life may have existed once in Mars' early history, and the identification of natural resources that could be mined and used for eventual human expeditions to the red planet. Autonomous rovers capable of traversing long distances, making in-situ measurements of soil and rock properties, and caching the samples for later return to Earth will be central to those scientific goals.
The Rocky 7 experiment team working with Hayati included scientists and engineers from NASA's Ames Research Center in Mountain View, Calif., Washington University in St. Louis, Mo., Cornell University, Ithaca, N.Y., and scientific institutions abroad. Most of the team congregated at the test site to observe Rocky 7's performance in the 29 Palms Marine Corps Base near Palm Springs, Calif. The site was chosen because it is a playa, not unlike some regions of Mars, with flat areas, mud-cracked areas, regions strewn with basalt rocks and numerous craters and ejecta generated by Marine Corps shells.
The Rocky 7 rover represents the newest, super-deluxe model of rover, but looks very similar to its predecessor, Sojourner, which is currently on its way to Mars. Rocky 7 weighs slightly more at 15 kilograms (33 pounds) compared to Sojourner, which weighs a petite 11.5 kilograms (25 pounds). The Rocky 7 robotic vehicle stands about as tall and has about the same dimensions as Sojourner, measuring 48 centimeters (19 inches) wide by 64 centimeters (25 inches) long by 32 centimeters (12.5 inches) tall. The rover also sports the same six-wheeled chassis and springless "rocker-bogie" mobility system, which allows the vehicle to conform to the contours of the surface and scale objects almost as tall as itself without tipping over.
Rocky 7 carries a 32-centimeter (12.5-inch) long manipulator arm with four degrees of freedom. Mounted on the front of the vehicle, the arm can reach 10 centimeters (4 inches) below the surface. Among its many uses, the arm will help scientists determine whether there are traces of water locked beneath Mars' polar ice caps or buried deep inside its crust.
Engineers have also fashioned a new 1.5-meter (5-foot) tall, antenna-like mast, which would be deployed once the robot was out and about on Mars. The mast has three degrees of freedom and carries three cameras: a pair of wide-angle stereo imagers for panoramic shots of the landscape and a narrow-angle imager for close-up shots of rocks and other geologic features. The mast can be used in much the same way as an arm, deploying science instruments against rocks or aligning them in the nadir, or down-pointing, position.
During testing, Rocky 7 carried all three cameras on its mast, in addition to a spectrometer on its digging arm and a pair of stereo imagers on the front and back of the vehicle, which acted as its "eyes." The rover was furnished with simulated descent imaging to recreate landing, then asked to deploy its mast and take a panoramic photograph of the landscape. Part of the field testing also involved demonstrating how well the rover could be controlled remotely from JPL using a World Wide Web operator interface, called the Web Interface for Telescience (WITS).
"The data system worked very well and the images that were delivered to the team were quite adequate," said Dr. Ray Arvidson, science team leader from Washington University. "Once the panoramic image was shot, the rover proceeded to traverse over a fairly smooth surface, using its hazard avoidance software to avoid obstacles.
"If you compare Rocky 7's first traverse of more than 200 meters (655 feet) to Sojourner's capability, you'll see the improvement," he said. "Sojourner can only travel tens of meters around the immediate landing site and relies 100 percent on a companion lander to relay and receive information. Rocky 7, on the other hand, is not only capable of roaming greater distances but is far more autonomous. Eventually, this new robot will be able to go over the horizon and conduct a full day's worth of in-situ experiments entirely on its own."
In addition to the navigation and mobility tests, a class of sixth graders from Eagle View Middle School in Colorado Springs, Colo., performed a remote commanding experiment. The students sent commands from their classroom to the rover. A local computer systems integration company, 3SI of Englewood, Colo., assisted in setting up the software interface for the remote operations experiment.
"The students sent commands to Rocky 7 over the Internet to carry out a 'dig and dump' experiment using the rover's robotic arm," said Dr. Paul Backes, a JPL engineer on the remote operations team. "The students commanded the rover to traverse through selected waypoints and then to use its robotic arm to scoop up some soil near one of the craters at Lavic Lake, and then dump it out. They then commanded another traverse and a science image task, and they were able to view the image that the rover took with its camera.
"All of this was done remotely using WITS, which was accessible from a common Web browser that scientists on a future rover mission might use," Backes said. "This distributed data and command system will allow scientists to participate in future planetary rover missions from their home institutions."
Pictures of the students in their classroom are available on the Internet at http://robotics.jpl.nasa.gov/tasks/scirover/operator/fieldTests/lavicDec96/eagleView.html.
Results of the Rocky 7 field tests will also be documented and posted on the Internet in a variety of formats as soon as they are available. Internet users may access the results at http://wundow.wustl.edu/rocky7/.
The Rocky 7 rover development and field testing was supported by JPL's Robotics and Mars Exploration Technology Program Office for NASA's Office of Space Science, Washington, D.C.
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