Introductions
On December 11, 1998, NASA launched the Mars Climate Orbiter (MCO). The mission of the MCO was to gather Martian climate data and serve as a relay station for the Mars Planet Lander (MPL), which would follow shortly thereafter. For nine months the MCO traveled through space. Some unplanned course corrections were executed during the trip, but no major issues were identified. On September 23, 1999, the MCO entered Martian atmosphere. It began an orbit that would take it temporarily out of radio contact behind the planet, as expected. The satellite was never heard from again.
Subsequent investigation revealed that a systemic failure caused the MCO to enter the atmosphere at an altitude approximately 100 miles lower than planned. The failure was traced to thrusters designed to use Metric units but supplied data programmed in English units. The satellite may have incinerated in the Martian atmosphere or continued traveling through space, unable to communicate with Earth.
The Mars Climate Orbiter Mishap Investigation Board was commissioned to investigate what happened. This investigation report identified 8 contributing causes that allowed the units problem to remain undetected .lists these contributing causes. A selected set of these items will be discussed in this paper and suggestions will be made to address them. This paper will also examine the concept of Intellectual Bias as it applies to the loss of the MCO. The investigation report also proposed 15 general recommendations for mitigating problems in the future. These recommendationsare, in the main, generalizations that require specific mappings into existing processes used by NASA.The general recommendations are enumerated .
An XML-formatted file could be contrived to specify English/Metric as well as specific units of measure for all the values in the file.illustrates how such an XML file might be structured.
Metric
Newtons
X
100