There are no gas stations on Mars and no clerks to give you directions.
In layman terms, Rongxing Li, creates maps. But for NASA’s twin Mars rovers, he is as close as it comes to a Martian tour guide.
Li, an Ohio State mapping expert, was recently awarded a three-year $900,000 contract from the National Aeronautics and Space Administration to continue developing navigation technology for possible use in NASA’s 2009 Mobile Science Lab mission.
“We were pretty confident we would get (the contract),” said Kaichang Di, a research associate who has been working with Li for four years.
Li, along with NASA’s Jet Propulsion Laboratory, created Ohio State MarsMapper, a software system being used to help rovers Spirit and Opportunity traverse the Red Planet.
To be considered for the 2009 mission, which will have a single rover larger than Spirit and Opportunity, Di said the research team must demonstrate that their technology and software are mission ready.
The MarsMapper software, which uses photogrametry, a method of extracting information from photographs to create maps, will have to be updated to include orbital images and more automatic data processing.
With just over a four-year gap between now and the next mission, there is plenty of time to make the software “bulletproof,” said Joy Crisp, lead project scientist for the current Mars mission.
The original mission estimated the rovers would travel half a mile and stop functioning after 90 days. Nearly nine months later the rovers have traveled a combined distance of five miles and are currently in an extended mission that will come to an end this month. There is also the possibility of another six-month extension, Crisp said.
To date the two rovers have taken over 50,000 images. LI’s team, which concentrates on photographs taken from four mounted cameras with a 360 degree turning radius, use the software to analyzes and create 3-D maps of the surrounding terrain.
“What we did was collect two adjacent pictures and overlap them,” said Xutong Niu, a graduate teaching associate who compared the process to how human eyes work.
These maps were then used by scientists and engineers to direct the rovers.
According to the OSU research team, their software corrected the estimated position of the rovers by as much as 13 percent in the case of Opportunity.
Mars’ loose sandy surface poses a problem for the rovers onboard odometers, which can be inaccurate because of slippage, a term used when a rover’s wheels spin through the soil without moving the robot.
Li, described by his students and colleague as a strict and capable man who gives good advice, realized rover navigation could be improved in 1997 when he watched the Mars Pathfinder rover exploration on TV. He contacted NASA with a proposal and was selected as one of 28 participating scientists.
Li travels between the laboratory and OSU and has been working on not just eastern and pacific times zones but also sol, the equivalent of a Martian day (24 hours and 40 minutes).
For the first 93 days the mission scientists worked on sol, coming to work 40 minutes later each day.
“It was a killer,” Crisp said.
When asked how it felt to be a part of the Mars mission Li said it he was excited and that it was a once-in-a-lifetime experience for a researcher.
“After so many years of work, we wanted it to be successful.” Li said about the January 3 landing of Spirit.
