Research Feature . . .
MAPPING SCIENTISTS TO HELP MARS ROVERS NAVIGATE
by Pam Frost Gorder
Despite its name, Silver Lake, CA, is anything but a lush, watery retreat. When Ohio State mapping scientist Ron Li ventured to that long-dry lakebed in the heart of the Mojave Desert, he might as well have stepped onto the surface of Mars.
NASA recently chose Li, professor of civil and environmental engineering and geodetic science, as a scientist for its Mars Exploration Rover (MER) 2003 mission. His team has traveled to the harsh environment of Silver Lake several times to test an innovative new mapping and localization system for two robotic rovers the space agency plans to launch in 2003. If all goes well, the six-wheeled rovers will roll out of their landing vehicle and prowl the Martian landscape in 2004.
Li's involvement with the program began in 1997, when he approached NASA with ideas for new computerized navigation techniques. Two years later, his team and collaborators at NASA's Jet Propulsion Laboratory (JPL) braved the punishing sun, sand dunes, and jagged rocks of Silver Lake, to test their system on the latest prototype rover.
"The only shade was inside our SUV," Li said, laughing as he recalled the field tests. "We drank a lot of bottled water."
The success of the mapping and rover localization system used at Silver Lake and later tests didn't guarantee NASA would choose Ohio State over the many competing research teams.
"We weren't the only game in town," Li said.
He and Kaichang Di, postdoctoral researcher and co-investigator on the project, feel especially honored to be chosen, since the mapping and rover localization system is critical to the rovers' operation.
"The rovers are solar powered, so each carries solar panels on top," he said. "If they were to climb a rock mistakenly because of poor mapping and navigation and tip over, they couldn't get any energy. The whole mission would just stop."
At the same time, the new MER rovers will face more challenges than the Sojourner robot did when it explored the red planet in 1997. NASA plans to collect many more samples of the Martian surface, over a wider area. The rovers will search for evidence of water as well as signs of possible ancient life on the planet, traveling as far as a kilometer over the 90-day lifetime of the mission.
With the help of digital mapping products, the rovers will find their way to specific target locations at the landing site that were chosen by NASA scientists. The robots will take core samples from rocks and from the surface itself, analyze the samples on-site, and transmit the data back to Earth.
The navigation system Li and Di are developing uses software to cross-match high and low altitude images -- taken by the rovers' landing vehicle as it descends to the surface -- with images the rovers will record once they are on the ground. Each Martian night, while the solar-powered rovers are at rest, the research team will use that day's images to incrementally map the landing site and plot the next day's path.
As one of the 28 selected participating scientists of MER 2003 mission, Li will collaborate throughout the project with engineers at JPL in Pasadena. In particular, he will work with Larry Matthies, supervisor of JPL's machine vision group.
Li and Di will travel to Pasadena during the rover operation period in 2004, but hope that their team -- including Fengliang Xu and other research assistants -- will conduct some of the work in Columbus. Here they can be involved in an extensive outreach program with ohio state undergraduates and local high school students.