ESA tests self-steering rover in 'Mars' desert
(麻豆淫院) -- ESA assembled a top engineering team then challenged them to devise a way for rovers to navigate on alien planets. Six months later, a fully autonomous vehicle was charting its own course through Chile鈥檚 Mars-like Atacama Desert.
The recent test of the Seeker full-scale rover was the outcome of gathering a multidisciplinary team at a single site, working against the clock to achieve a breakthrough.
鈥淭heir challenge was to demonstrate how a planetary rover 鈥� programmed with state-of-the-art software for autonomous navigation and making decisions 鈥� could traverse 6 km in a Mars-like environment and come back where it started,鈥� explained ESA鈥檚 Gianfranco Visentin.
Long-range rovers risk getting lost
Mars rovers cannot be 鈥榙riven鈥� from Earth 鈥� it takes radio signals up to 40 minutes to make the trip to Mars and back. Instead, they are given instructions to carry out autonomously.
鈥淓SA鈥檚 ExoMars rover, due to land on Mars in 2018, will have state-of-the-art autonomy,鈥� added Gianfranco.
鈥淗owever, it will not travel more than 150 m each martian day and not much more than 3 km throughout its mission.
鈥淭he difficulty comes with follow-on missions, which will require daily traverses of five to ten times longer.
鈥淲ith longer journeys, the rover progressively loses sense of where it is.
鈥淟acking GPS on Mars, the rover can only determine how far it has moved relative to its starting point, but the errors in 鈥榙ead reckoning鈥� build up into risky uncertainties.鈥�
The team aimed at fixing their position on a map to 1 m accuracy. Seeker used its stereo vision to map its surroundings, assess how far it had moved and plan its route, making sure to avoid obstacles.
Desert testing
First, prototypes were tested indoors and outdoors. Then, in May, the Seeker team took their rover to the Atacama Desert, one of the driest places in the world 鈥� selected for its similarities to martian conditions.
鈥淭he European Southern Observatory鈥檚 nearby Very Large Telescope was an additional advantage,鈥� Gianfranco added. 鈥淭he observatory kindly provided refuge for the cold and windy desert nights.鈥�
For two weeks the team put the rover into action within a particularly Mars-like zone. Like anxious parents, they watched the rover wander out of sight, maintaining only radio surveillance.
Their daily efforts culminated in the final trial, when Seeker was programmed to perform a 6 km loop.
鈥淚t took a whole day because the rover moves at a maximum 0.9 km/h,鈥� Gianfranco recalled.
鈥淏ut this was an unusual day. The usual desert winds counteracting the fierce heat of the Sun died away.
鈥淭he rover grew dangerously warm, and had to be stopped around midday. Then, when the wind finally picked up there wasn鈥檛 enough time to complete the loop before sundown.
鈥淲e 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鈥檚 first large-scale rover test 鈥� though definitely not our last.鈥�
Provided by European Space Agency
