June 19, 2012
ESA Tests Out Rover In Chile Desert
Lee Rannals for redOrbit.com
A challenge that ESA set out to have an engineering team create a rover that could steer itself in a Martian desert has finally been met.
“Their challenge was to demonstrate how a planetary rover — programmed with state-of-the-art software for autonomous navigation and making decisions — could traverse 6 km (3.7 miles) in a Mars-like environment and come back where it started,” ESA´s Gianfranco Visentin said.
Mars rovers are unable to be "driven" from Earth because it takes radio signals up to 40 minutes to make the trip to Mars and back. Scientists instead give out instructions for the rovers to carry out.
“ESA´s ExoMars rover, due to land on Mars in 2018, will have state-of-the-art autonomy,” added Gianfranco. “However, it will not travel more than 150 m (500 feet) each Martian day and not much more than 3 km throughout its mission."
He said the follow-up missions will be the difficult part because they will require daily traverses of five to ten times longer.
“With longer journeys, the rover progressively loses sense of where it is," Visentin said in the statement. “Lacking GPS on Mars, the rover can only determine how far it has moved relative to its starting point, but the errors in ℠dead reckoning´ build up into risky uncertainties.”
The engineers fixed their position on a map to about 3-feet of accuracy. Their rover used its stereo vision to map its surroundings and assess how far it had moved to plan its route.
The team took out their rover Seeker to the Atacama Desert in May after testing out prototypes in indoor and outdoor tests. The Chilean desert is one of the driest places on Earth and has similar conditions as Mars.
“The European Southern Observatory´s nearby Very Large Telescope was an additional advantage,” Gianfranco added. “The observatory kindly provided refuge for the cold and windy desert nights.”
The engineers set out Seeker within a Mars-like zone, and watched as it wandered out of sight. At that point, they maintained only radio surveillance of the rover.
They set the rover on about a 4 mile loop for the final trial, but had to stop the mission short due to the weather.
“But this was an unusual day. The usual desert winds counteracting the fierce heat of the Sun died away," Visentin said. “The rover grew dangerously warm, and had to be stopped around midday.
He said that when the wind finally picked up and the heat cooled-off, there was not enough time to complete the loop before sundown.
“We managed 5.1 km, somewhat short of our 6 km goal, but an excellent result considering the variety of terrain crossed, changes in lighting conditions experienced and most of all this was ESA´s first large-scale rover test — though definitely not our last," said Visentin.