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.”
Unexpected plans
During the Martian night, dozens of scientists, including Gupta, anaylse the images and data coming back from the Red Planet and discuss what they want to do next. They hold a series of meetings to prioritise time on the instruments, choose which images to capture and where the rover’s going to move.
“It’s quite complicated because you have to work out how much power each instrument is going to use and how much heating time they require,” Gupta says. “Because they’re so many instruments, everybody wants to have a go – so one instrument might get five minutes, another ten minutes.”
Once the arguments are had and decisions reached, the drivers get to work, coding the next day’s instructions. And this is way more complicated than programming one of those ‘80s-era Big Trak robot toys.
Curiosity is the fourth rover (since the 1996 Pathfinder mission) Nasa has run on Mars in recent years, and the procedures have got better with every mission. Armed with 3D images from its navigation cameras, the drivers work through the Martian night to map out the best, smoothest, route to the next destination. They factor in any stops along the way, to take pictures or operate an instrument, and run a simulation of the journey to double-check they have got it right.
