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									Controlling Curiosity: How do you drive a
Mars rover?
        Engineers at Nasa’s Jet Propulsion Laboratory (JPL) in Pasadena, California, have the
ultimate iPhone app. But it’s not something you will find in the App Store. With a few taps on
the screen, I can send a replica of Nasa’s Curiosity rover trundling - at a slow walking pace -
across the rocky terrain of JPL’s outdoor test area, known as Mars Yard.I find myself treating the
experience like a video game: starting out cautiously with a few gentle turns, before
commanding the car-sized rover to cross some sizable boulders. Mobility test engineer Daniel
Fuller calls ‘game over’ when I manage to ground one of the vehicle’s six wheels on a
particularly large lump of stone.

       Thankfully the real rover, some 200 million kilometers (125 million miles) away on the
Red Planet, is in safer hands. And the way it’s driven is rather different.“It’s a common
misconception that we’re just ‘joysticking’ it or we’re driving and sending these commands and
we’re suffering a 15 minute delay,” says Fuller, who divides his time between the rover control
room and Mars yard. “We actually plan an entire day – or a sol as it’s called on Mars.”Each of
these daily missions is overseen by people like Sanjeev Gupta from Imperial College London.
When I meet him, the geologist and senior member of the JPL science team is living on Mars
time.

        “During the Mars night we prepare the sequences the rover has to do,” he explains. “Then
we uplink those commands and, when the rover wakes up, it carries out those tasks. But a Mars
day is 40 minutes longer than an Earth day so you get progressively out of synch, so the time I
arrive at work changes by an hour every day.”And that’s not all. “We don’t get a signal direct
from the rover to Earth,” says Gupta. “It has to go through communications satellites - Mars
Reconnaissance Orbiter (MRO) and Odyssey - and these obviously have different times [when
they’re overhead].”“Generally you’re moving an hour forward each day but suddenly, like
tomorrow, I’m going to step back two hours. I’m progressively getting used to it but the first
three weeks were awful,” he groans, “I was permanently exhausted.”

								
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