Design

• Every spacecraft is a sophisticated, custom-made piece of equipment. During its design, engineers use computers to plan out its many thousands of parts. Large teams of engineers, technicians and managers share the computer files, approving one assembly after another until they complete the design. After they build it, they create automated tests run by computers, simulating the vibration, cold and vacuum the craft will encounter in space. When it passes the tests, it is ready for launch.
  
  

Planning

• A spacecraft may travel billions of miles on its mission. Since there are no refueling stations out there, the craft must carry all its fuel with it. Planning a fuel-efficient mission takes very high priority. Scientists play a game of celestial "pool," aiming the space probe along a precisely-defined path that takes it near neighboring planets. The craft picks up speed as it approaches a planet. The path must be computed and timed very exactly, taking into account the motions of the craft and all the planets involved. While missions that use this strategy take longer, they use a fraction of the rocket fuel.
  
  

Diagnostics

• When a Mars rover develops a problem, you can't send a repair crew 40 million miles to fix it. The engineers that built the rover understood this and included computers and software to check its status and run diagnostic tests. If a wheel gets stuck, for example, the computer will note that its rotation is different than the other wheels and report a problem to the mission team on Earth. The team may have the rover computer check the wheel's motor and plan a strategy to free the stuck wheel.
  
  

Navigation

• Deep-space missions take many years. During that time, the spacecraft travels many millions of miles on a complex path that may visit several planets. A computer on the spacecraft communicates its speed, direction and location back to Earth. At critical times, it will fire navigation rockets to adjust its course. Since radio signals can take minutes to hours to reach the craft, the computer must manage some maneuvers on its own, informing the mission team of its progress along the way.
  
  

Robotics

• The cost of a robotic mission to another planet is far less than a manned mission, so robotic explorers have become the mainstay of deep space research. On-board computers control a robot's various functions, including power management, communications, movement and analysis. During the course of a mission, the project team can send the computers new programming and data, so the robot can better handle changing conditions.