With remote control of rovers on Mars out of the question due to radio signals taking up to 40 minutes to make the round trip to and from the Red Planet, the European Space Agency (ESA) has developed a vehicle that is able to carry out instructions fully autonomously. The ESA team recently tested their Seeker full-scale rover in Chile where the rover was able to chart its own course through the Mars-like Atacama Desert.
The multidisciplinary team, which was put together by the ESA just six months ago, was challenged with demonstrating a planetary rover that could autonomously make decisions, traverse six kilometers (3.7 miles) in a Mars-like environment, and return to its starting point. With Mars lacking any GPS satellites to help with navigation, the rover must determine how far it has moved relative to its starting point. However, as ESA’s Gianfranco Visentin points out, any errors in this “dead reckoning” method can “build up into risky uncertainties.”
To minimize any uncertainties, the team sought to fix the rover’s position on a map to an accuracy of one meter (3.28 ft). To build a 3D map of its surroundings, assess how far it had traveled and plan the most efficient route to avoid obstacles, Seeker relied on its stereo vision.
After the prototypes were tested indoors and out, the team took Seeker to the Atacama Desert in May. Over a two-week period, the team put the rover through its paces, maintaining only radio surveillance as the rover traveled out of sight. The tests culminated with a final trial that saw Seeker programmed to perform a six-kilometer loop.
With the rover only traveling at a maximum speed of 0.9 km/h (0.56 mph), the journey would have taken all day. Unfortunately weather conditions weren’t ideal, with the desert winds that help to counteract the heat of the Sun dropping away during the day.
“The rover grew dangerously warm, and had to be stopped around midday. Then, when the wind finally picked up there wasn’t enough time to complete the loop before sundown,” said Gianfranco. “We managed 5.1 km (3.16 miles), 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.”
Gianfranco points out that the ExoMars rover that is due to land on Mars in 2018 will not travel more than 150 m (492 ft) per Martian day and not much more than three kilometers (1.86 miles) over the course of its mission.
“The difficulty comes with follow-on missions, which will require daily traverses of five to ten times longer,” he says. “With longer journeys, the rover progressively loses sense of where it is.”
The Seeker testing in the Atacama Desert is designed to help the ESA team meet these challenges.