A test prototype of ESA's ExoMars 2020 Mars rover is getting a workout in Spain's Tabernas Desert – which is odd because mission control was a thousand miles away at the Harwell Space Cluster in Oxfordshire, England. The ExoFit rover, called "Charlie," was tasked with testing hardware and software for the final Mars rover set to fly in 2021 and the practice science operations.

Building an autonomous rover to explore the Red Planet involves a lot more than just drawing up plans, writing some software, then slapping it together and sticking it atop a rocket after a few bench tests. Because it will be over a hundred million miles away on a planet where it takes up to half an hour for a radio signal to reach it, each rover must be tested and retested under realistic conditions to be certain that it's both up to the job and able to be properly controlled from Earth.

That's the function of ExoFit Charlie. Under remote orders from Harwell, the British-built rover has conducted its first tests on a simulated Martian surface. These included driving off its lander ramp, identifying a geological outcrop at a distance, moving toward it, and taking a sample with its drill.

The purpose of these tests is to see how Charlie works as a whole as well as prove its individual subsystems. These include the WISDOM ground penetrating radar, CLUPI close up imager, and the Panoramic Camera (PanCam) mast imager for creating stereographic maps to help guide the rover and drilling arm. In addition, it allows the team to figure out better ways of working with the robotic explorer. This is particularly important because the time lag means that the ExoMars 2020 rover will be more of a partner than a puppet.

"One of the primary goals of ExoFiT is the setup of efficient remote science operations," says Ben Dobke, Airbus project manager for ExoFiT. "It will allow the team of instrument scientists and engineers to practice how to remotely operate and interpret the data from rover mounted instruments. It is set up as a blueprint to develop operational experience for both ExoMars and future robotic Mars missions."

For the tests, which are still ongoing, each science team has a remote operator at the Science and Technology Facilities Council Harwell Mission Operation Centre's Remote Control Centre for Charlie, where they work with digital maps and limited information sent each day by the rover from Spain. This allows them to interact under the same realistic constraints that they will face on Mars.

According to the UK Space agency, the current series of tests will be followed up in 2019 by field tests in the Atacama Desert in Chile – the driest and most lifeless place on Earth, where even bacteria can't survive. This will help the ExoMars mission as it ramps up to be the first to actually dig down into the Marian surface to look for direct evidence of life since the NASA Viking missions that landed in 1976.

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