{"UUID":"7102ef9a-a7ae-4215-a8fe-167a4a8c1de3","URL":"https://en.wikipedia.org/wiki/Mars_Climate_Orbiter","ArchiveURL":"","Title":"Mars Climate Orbiter unit conversion failure","StartTime":"1998-12-11T18:45:51Z","EndTime":"1999-09-23T09:04:52Z","Categories":null,"Keywords":["mars climate orbiter","nasa","lockheed martin","unit conversion","metric","imperial","spacecraft","mission failure"],"Company":"NASA","Product":"Mars Climate Orbiter","SourcePublishedAt":"2003-09-09T18:07:38Z","SourceFetchedAt":"2026-05-04T17:49:23.077695Z","Summary":"Use of different units of measurement (metric vs. English) caused Mars Climate Orbiter to fail. There were also organizational and procedural failures[[ref](https://space.stackexchange.com/a/20241)] and defects in the navigation software[[ref](https://spectrum.ieee.org/aerospace/robotic-exploration/why-the-mars-probe-went-off-course)].","Description":"The Mars Climate Orbiter, launched on December 11, 1998, was a robotic space probe intended to study the Martian climate and serve as a communications relay. On September 23, 1999, during its critical orbital insertion maneuver around Mars, communication with the spacecraft was permanently lost. The orbiter entered the Martian atmosphere at a significantly lower altitude than planned, leading to its destruction or re-entry into heliocentric space.\n\nThe primary cause of the failure was a measurement mismatch between two software systems. Ground software provided by Lockheed Martin calculated thruster impulse in pound-force seconds (US customary units), while a separate NASA system expected these results in newton-seconds (SI units), contrary to the Software Interface Specification. This unit discrepancy resulted in incorrect trajectory calculations, causing the spacecraft to approach Mars at an unsafe altitude.\n\nNASA acknowledged its own responsibility for failing to implement adequate checks and tests that would have detected this critical error. Concerns raised by navigators regarding the trajectory discrepancy were reportedly dismissed. The mission's failure led to the complete loss of the spacecraft and its scientific objectives, which included studying the Martian atmosphere and surface changes, and providing communication support for the Mars Polar Lander.\n\nThe incident was investigated by the Mars Climate Orbiter Mishap Investigation Board. Although not explicitly detailed as remediation, the article notes that the Mars Reconnaissance Orbiter later accomplished most of the original mission objectives. The failure also brought to light underlying issues such as inadequate funding and poor management within the Mars Surveyor '98 program."}