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12 Autonomous navigation software for a rover destined for Mars has passed initial tests at the European Space Agency (writes Nick Flaherty). A half-scale version of the rover, called the ExoMars Testing Rover (ExoTeR), manoeuvred through rocks and sand at the 9 x 9 m Planetary Utilisation Testbed, part of the ESA’s Planetary Robotics Laboratory at the ESTEC research centre in the Netherlands. Calculating its onward route, the AutoNav software allowed the ExoTeR to move at 2 m per minute, several times faster than the actual ExoMars rover, which will progress at 100 m per Martian day (which is about 37 minutes longer than an Earth day). The two-day test was conducted by ESA robotic engineers, joined by a team from France’s space agency CNES in Toulouse. “Rather than sending complete hazard- free trajectories for the rover to follow, autonomous navigation allows us to send it only a target point,” said Luc Joudrier at the ESA. “The rover creates a digital map of its vicinity and calculates how best to reach that target point. Looking at the map, it tries to place the rover in all the adjacent locations to work out if it would be safe in every one of them, or if the rocks are too high or terrain too steep. “Working from the local navigation map, the rover computes a safe path towards the goal and begins to move along a segment of the calculated path. At the end of the segment it repeats the same mapping process to progress,” he added. Previous rovers used the turn of the wheels to determine the distance travelled. This software however uses vision-based motion tracking from a stereo camera on the rover. That allows the navigation algorithm to take account of any wheel slippage if, for example, the rover is caught in deep sand. The ExoTeR was developed during 2017 by Altec in Italy, the site of ExoMars’ rover monitoring and control centre, coming to ESTEC last December. It will now return to Altec, allowing the control team to gain experience with the added functionality of autonomous navigation ahead of ExoMars’ flight software being completed. ExoMars’ final flight software will actually carry two sets of autonomous navigation software, with another developed by Airbus in Stevenage, UK. “The combination should give the rover added flexibility,” said Joudrier. “The idea is that one might turn out to perform better in more difficult terrain, while the other could move faster along easier ground.” Mars navigator hits target Space systems February/March 2019 | Unmanned Systems Technology Testing the ESA’s ExoMars Testing Rover with its autonomous navigation software (Courtesy of ESA)