$ 125 million, crash on Mars.
Poor communication, lack of testing.
The Mars Climate Orbiter was intended to enter orbit at an altitude of 140-150 km above Mars. However, a navigation error caused the spacecraft to reach as low as 57 km. Contact was lost and never re-established, and no further signal was ever received from the spacecraft.
Findings of the failure by the review board indicate that the navigation error was caused by the reporting of spacecraft data in imperial instead of metric units. This caused the spacecraft to miss its intended 140–150 km altitude above Mars during orbit insertion, and instead to enter the Martian atmosphere at about 57 km. At this low altitude, the spacecraft was destroyed by atmospheric stresses and friction.
The metric/imperial mix-up that destroyed the craft was caused by a human error in the software development, back on Earth. The thrusters on the spacecraft, which were intended to control its rate of rotation, were controlled by a computer that underestimated the effect of the thrusters by a factor of 4.45.
This is the ratio between a pound force (the standard unit of force in the imperial system) and a newton (the standard unit in the metric system). The software was working in pounds force, while the spacecraft expected figures in newtons (1 pound force equals approximately 4.45 newtons).
The software had been adapted from use on the earlier Mars Climate Orbiter, and was not adequately tested before launch. The navigation data provided by this software was also not cross-checked while in flight.
The Mars climate orbiter failure board released a report quoting the contributing causes of the failure of this project. These included inadequate consideration of the entire mission and its post-launch operation as a total system, inconsistent communications and training within the project, and lack of complete end-to-end verification of navigation software and related computer models.
In particular the board cited:
- the operational navigation team was not fully informed on the details of the way that Mars Climate Orbiter was pointed in space, as compared to the earlier Mars Global Surveyor mission
- some communication channels among project engineering groups were too informal
- the small mission navigation team was oversubscribed and its work did not receive peer review by independent experts
- personnel were not trained sufficiently in certain areas, such as the relationship between the operation of the mission and its detailed navigational characteristics, or the process of filing formal anomaly reports
- the process to verify and validate certain engineering requirements and technical interfaces between some project groups, and between the project and its prime mission contractor, was inadequate.