ESA teaches rover to fetch

The European Space Agency’s scientists and engineers are working on a self-navigating system for ESA’s first robotic ‘precursor’ mission, ExoMars, due for launch around 2011.

ExoMars will explore the biological environment on Mars in preparation for further robotic and, later, human activity. Data from the mission will also provide input for broader studies of exobiology, the search for life on other planets.

The main element of the mission is a wheeled, robotic rover vehicle, similar in concept to NASA’s current Mars Rover mission, but having different scientific objectives and improved capabilities.

The rover will use solar arrays to generate electricity, and will travel over the rocky orange-red surface of Mars, transporting an up to 12-kilogram experimental payload including a first-ever lightweight drilling system, as well as a sampling and handling device, and a set of scientific instruments to search for signs of past or present life.

Due to distance time-lag and complexity, ExoMars will self-navigate using ‘smart’ electro-optics to visually sense and interpret the surrounding terrain and will be capable of operating autonomously using intelligent onboard software.

In one typical example of the rover’s autonomous operation, ground controllers might radio up a high-level command telling it to drive to a scientifically interesting spot anywhere from 500 to 2000 metres away and conduct science operations, such as drilling beneath the surface to sample soil for life signs. But the vehicle would handle the details of the move on its own.

It would survey the ground with a 3D camera, create a digital terrain model, verify its present location, run internal simulations and then make an autonomous decision on the best path to follow, based on obstacles, the rover’s current status and risk/resource considerations.

“Then it will drive itself to the target. We expect its target accuracy to be within one-half metre over a traverse of 20 metres,” says Bob Chesson, head of the Human Spaceflight and Exploration Operations Department in ESA’s Operations directorate.

ESOC (European Space Operations centre) will serve as the overall mission operations control centre (MOCC), controlling the launch and early orbit phase (LEOP), the cruise to Mars, the separation and landing of the Descent Module and the Rover egress, with management of rover surface operations likely to be conducted from the Rover Operation Centre located at ALTEC, the Advanced Logistic Technology Engineering Centre, in Turin, Italy.

The ground control system will require computing facilities to enable high-level mission planning tools and to allow monitoring of the rover’s digital terrain and 3D modelling, ground path and trajectory planning, on-ground simulation and tight integration with the payload control and scientific operations.

“Classic direct control methods just won’t work when we operate on the surface of Mars in an unstructured environment and with a significant signal time delay, says Reinhold Bertrand,” a planning engineer and robotics expert at ESOC. “ExoMars will require a change in culture; we have to ‘let the child walk on its own’ while we develop a truly interdisciplinary operations concept.”