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Rover driver Eric Baumgartner is one of eight rover drivers. There are four for Spirit and four for Opportunity. Two rover drivers are on station for any given sol. "It's a lot of fun to come to work and drive the rovers on Mars and drive the rover arm, which is a whole other story in itself," said Baumgartner. The rover drivers for the two rovers have had very different experiences due to the difference in terrain at the two sites.
Image
right: Navigation camera image taken from Opportunity
on February 27. Notice the large tilt of the
horizon due to the success of the climb up
the outcrop. As Opportunity tilts up the slope,
the rover's cameras snap pictures at an angle.
Credit: NASA/JPL.
"At the Opportunity site, it's like we're driving on snow with little traction on the slopes, but the Spirit site is like monster truck driving with the rocky terrain," laughed Baumgartner.
Spirit is on flat, rocky terrain, while Opportunity is in steep terrain with a low distribution of rocks, so the two rover driving teams will be swapping lessons learned when each rover moves to a different location. "If Spirit makes it to Bonneville crater, the rover drivers will have to rely on what we've learned at Meridiani, and once we get out of the crater at Meridiani, we may need to learn how to drive far in a rock-strewn landscape from the Spirit team," said Baumgartner.
On Your Mark, Get Set, Rove!
In order to build the drive commands for Spirit and Opportunity, rover drivers use sophisticated software created at NASA's Jet Propulsion Laboratory to make a three-dimension simulation of the martian terrain using navigation camera images and a simulation of the actual movement of the rover. Rover drivers must simulate the rover movement in a computer program because there isn't enough time to sprint to a test bed (a sandbox with an engineering rover model) every day to run the command sequence. Schedules are extremely tight to turn around new, complex robot moves and send the commands to a planet over 150 million miles away.
Image
left: Spirit's traverse map after the rover had
driven 131 meters (430 feet) in 45 sols. Credit:
NASA/JPL/OSU/Cornell.
"We run many, many simulations -- up to 20 per move -- to figure out what the best path is for each segment of the drive," explains Baumgartner. Rover drivers for Opportunity have to add in the slippage estimates created by the mobility experts. Rover drivers use the slope information and tell the rover to stop short of its target when it's heading down a slope so that the rover will slide into home plate on its own. When the rover has to trek up a slope, engineers do the opposite since it is harder for the wheels to churn upward. If the rover needs to go up a slope, engineers command the rover to actually go farther than necessary to compensate for the upward tilt.
Image right: Screenshot of the software rover drivers
use to simulate the commands sent to the
rovers every sol. Credit: NASA/JPL.
"I didn't think adding in slippage would be part of my work as a rover driver," said Baumgartner. "The foresight of the mechanical team was tremendous, and if we didn't have the slippage chart, we would be putting our thumbs to the air and saying, ‘I think the rover will slip about this much here,'" laughed Baumgartner. "Within about five hours every day, we have to write hundreds of lines of commands to drive the rover to the scientists' dream location. Without the efficient slip estimates, which the mobility team constantly refines, we would be in a lot of trouble here," said Baumgartner.
Body Movin'
On February 18, the wake up song for Opportunity was ‘Body Movin' by the Beastie Boys in honor of the 15-meter (49-foot) drive, which was Opportunity's farthest distance to date. "We were off by less than 0.5 meters (1.6 feet) from our desired final destination, which is an error of about 3%. In contrast, Opportunity actually slipped between 10% and 17%, so without this slippage planning, we would have been off by as much as 2.6 meters (8.5 feet). That would have cost us another day on Mars to get close enough for the pancam and mini-TES work that was planned at the target," said Lindemann.
"We've moved from sad folk music to body movin' rap music for wake up songs, so I'm pretty happy," said Lindemann with a smile.
Watch a video of Testing the Rovers for the Treacherous Martian Terrain
More information about Moving Around on Mars
Mars
Exploration Rover Drivers |
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| Brian Cooper | Chris Leger | |
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| Eric Baumgartner | Frank Hartman | |
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| Jeff Biesiadecki | John Wright | |
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| Robert Bonitz | Scott Maxwell | |