In 1998, the National Aeronautics and Space Administration (NASA) launched the Mars Climate Orbiter (MCO) as part of the Mars Surveyor ’98 program. Upon arrival at Mars, MCO was to enter an elliptical orbit around the planet. On the day of orbit insertion, ground control was able to track the spacecraft visually up to the point when it vanished behind the planet. Unfortunately, the spacecraft never reappeared on the other side. It was later discovered that the probe came too close to the planet, and crashed into the Martian surface. The cause? A previously undiscovered mismatch in the use of unit systems for performing certain calculations in parts of the ground station software [43].