One team, two measurement systems, one huge definition mistake
On December 11th 1998 NASA launched the Mars Climate Orbiter. The probe was designed to measure water distribution on the surface of Mars. 286 days after launch the $328 million probe arrived at Mars. It missed the correct orbit by 100km. The probe dipped into the atmosphere, overheating the engine system. It crashed into the surface of Mars on September 23rd 1999.
A review concluded that NASA lost a Mars orbiter because a Lockheed Martin engineering team used English (we English call this measurement system 'Imperial', how confusing?) units of measurement while the agency's team used metric system for a key spacecraft operation. The units mismatch prevented navigation information from transferring between the Mars Climate Orbiter spacecraft team at Lockheed Martin in Denver and the flight team at NASA's Jet Propulsion Laboratory in Pasadena, California. In short, a definition mistake in the units led to the total loss of the mission.
Lockheed Martin helped build, develop and operate the spacecraft for NASA. Its engineers provided navigation commands for Climate Orbiter's thrusters in English (Imperial) units although NASA has been using the metric system since at least 1990.
A single mistake, involving something as basic as a definition mistake for the unit of measurement, unravelled years of engineering and science and and $328m investment.
It would be easy to blame the individuals involved, but this really represents a systemic failure.
- A failure of measurement definition.
- A failure of to react to multiple queries raised by engineers.
- A failure of the US to move completely over to the metric measurement system.
We can never be sure if properly constructed measure definitions would have prevented this catastrophe, but they certainly would have helped.
How can we avoid our own definition mistakes?
The good news is that measurement and KPI definition may be dull, but it's not hard. Here are some critical questions to get you started and a template to help you record your answers. With a little forward planning you should be able to avoid your own KPI version of the Mars Climate Orbiter.