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Communications of the ACM

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Mars Code

Mars Code, illustration

On August 5, 2012, 10:18 P.M. PST, a large rover named Curiosity made a soft landing on the surface of Mars. Given the one-way light-time to Mars, the controllers on Earth learned about the successful touchdown 14 minutes later, at 10:32 P.M. PST. As can be expected, all functions on the rover, and on the spacecraft that brought it to its destination 350 million miles from Earth, are controlled by software. This article discusses some of the precautions the JPL flight software team took to improve its reliability.

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To begin the journey to Mars you need a launch vehicle with enough thrust to escape Earth's gravity. On Earth, Curiosity weighed 900 kg. It weighs no more than 337.5 kg on Mars because Mars is smaller than Earth. Curiosity began its trip atop a large Atlas V 541 rocket, which, together with fuel and all other parts needed for the trip, brought the total launch weight to a whopping 531,000 kg, or 590 times the weight of the rover alone.

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