The Mars Climate Orbiter (MCO) was a space probe launched by NASA to study the MArtian climate, atmosphere, ands surface changes. It was lauched on December 11 1998, but the communication with the spacecraft was lost on September 23 1999, when the spacecraft went into orbital intersetion.
The reason of this communication failure was becase a ground-base computer software produced an output in non-SI units, while a second systems that used those results expected them to be in metric units. The software that calculated the total impulse produced by the thruster firings during the Trajectory Correction Maneuver-4 calculated the results in pounds-seconds, instead of the spected output of newtons-seconds. The trajectory alculation used these results to correct the predicted position of the spacecraft for the effects of the thruster firings. This unit error made the spacecraft to encounter Mars on a trajectory that brough it too close to the planet, which cuased the spacecraft to desintegrate due to atmospheric stress when passing through Mars upper atmosphere.This error was previously noticed by at least two navigator, whose concerns were dismised. The execution of Trajectory Correction Maneuver- 5 was then considered, which was also in the schedule, but it was ultimately not done.
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