The importance of being precise – inaccuracy and the crash of NASA’s Mars Climate Orbiter
Getting the details right
On 23 September 1999 the missions team at NASA should have been celebrating as the Mars Climate Orbiter successfully entered stable orbit. Instead they watched as the Orbiter flew too close to the surface and vanished from communications forever. The failure was caused by a simple conversion error between metric and imperial measurement systems and demonstrates how vital it is, particularly in mission-critical industries such as space exploration, to get the small things right.
Mars Climate Orbiter
The Mars Climate Orbiter was a small robotic space probe designed and built by Lockheed-Martin Astronautics with a navigation system created by Jet Propulsion Laboratories. Launched on 11 December 1998 it was designed to study the Martian climate, surface and distribution of water. It was also intended to act as the communications relay for the Mars Surveyor ‘98 Lander, launched three weeks later.
Smaller, lighter, faster spacecraft
At the time NASA was strongly focused on reducing the time and cost of space exploration projects. The Orbiter should have been a shining example of its ability to produce smaller, lighter spacecraft for a lower budget, but instead a simple miscalculation caused it to fly within 37 miles of Mars’ surface and disappear, presumably broken apart or burned up, and completely ruining NASA’s day.
Metric v imperial
When designing the Orbiter Lockheed-Martin used the imperial system in its calculations, expressing force in pound-seconds. Although it was standard practice to convert calculations to metric for space missions Lockheed Martin did not make the conversion. JPL navigation software engineers assumed the figures had been converted and made their own calculations in metric newton-seconds. The systems engineering function, responsible for checking all aspects of the project, failed to spot the error and the Orbiter’s fate was sealed.
Consequences
Metric conversion errors can be a problem in other industries, including oil and gas where projects frequently use a variety of different measurement systems. Other occurrences such as the Gimli Glider incident in 1983, where a jet ran out of fuel mid-flight and had to glide the last 100 miles, or medical prescription miscalculations show the potentially catastrophic consequences of a small error in measurement. The most sophisticated technology, equipment or medicine will fail if the measurements are wrong.
Further lessons
The metric mix-up was not the only reason the Mars Climate Orbiter failed. Cultural issues and communication failures played a significant role, as demonstrated further when the Mars Surveyor ’98 Lander was also lost – for different technical reasons this time, but affected by the same culture-based problems.
Systems failure
NASA carried out a comprehensive investigation into the failures and concluded that although the calculation error originated with Lockheed-Martin, it was not to blame. Although both Lockheed-Martin and Jet Propulsion Laboratories recognised their role in the disaster, NASA concluded that ultimate responsibility lay within. Accepting that human error should be expected NASA placed the blame with its own systems, which were not robust enough. Prior to launch navigation specialists had tried to raise concerns only to have them dismissed for bureaucratic reasons. Meetings had been held at which trajectory correction measures were suggested but never undertaken. Focus on reducing costs had caused too many corners to be cut.
Robust inspection culture
The combination of a calculation error with these cultural failings caused the loss of a $125m space exploration mission (rising to $285m when fuel and launch costs included). An open culture with robust inspection, reporting and checking procedures in place is vital for successful business operations in industries such as space exploration and oil and gas. Click here to read our blog on the value of third-party inspection.
Since the Mars Climate Orbiter and Surveyor ’98 failed NASA has revolutionised its culture and successfully launched the Mars Exploration Rovers Spirit and Opportunity, which completed their six-month missions and are still operational today.
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Posted 27.01.20
[5 minute read]