Unit mix-up sinks NASA's Mars Climate Orbiter after nine months in space

NASA’s Mars Climate Orbiter, a $125 million mission, was lost after nine months in space when one ground team used English units and another expected metric, delivering pound-force-seconds instead of metric newton-seconds and steering the orbiter onto a too-low Mars approach. The error, compounded by solar radiation pressure, tracking blind spots, and a breakdown in anomaly reporting, was later attributed by a Mishap Investigation Board to eight contributing factors, with the measurement mismatch as the root cause. The incident led to safety reforms and ongoing lessons for future Mars missions, including the later Mars Polar Lander loss.