The Mars Climate Orbiter failed due to a metric-imperial unit conversion error. The spacecraft's software used metric units while ground teams entered data using imperial units, resulting in incorrect calculations that sent the orbiter too low into Mars' atmosphere, where it disintegrated. The failure was caused by human error in not ensuring consistent use of units across software and teams. It underscores the importance of strict protocols and training to prevent mistakes when using different measurement systems.

1. MarsClimate Orbiter Failure So what exactly happened on The Mars Climate Obiter? It suffered a tragedy in 1999 when it entered too high into the atmosphere and disintegrated! Read more to find out more about why this happened and what should have been done to prevent this from happening again. Ye Jiadong (29)1A1 Science ACE

2. Mars Orbiter (December 11, 1998 to September 23, 1999) It was clearly a tragic accident. An accident that had to do with the metric and imperial system conversion mix up. But human error was mostly at fault. Just like Air Canada’s Gimli Glider, the ground crew were not given enough training for the metric system. Although, the only difference was that this Mars Obiter accident had nothing to do with technology or computer failure. It was mainly cause by human error. On the December 11 1998, Mars Obiter was launched in the Cape Canaveral Air Force Station and it was to cover up the mission of the Mars Observer which also met with a tragic ending when its fuel pump ruptured. It was supposed to study Mars, its probability for water sources, the weather, temperature, atmospheric effects, climate change and lastly, water vapour and dust content of Mars. The Obiter was very modernized, with standard equipment installed in it, with also thrusters for speed gain and travelling through space. The Obiter was supposed to start its insertion maneuver on September 23, 1999. However, the obiter lost contact as it had encountered Mars at a very low altitude, and disintegrated due to atmospheric stress.

3. Investigations So, what exactly caused this accident? Metric and Imperial systems, called a metric-mix up. When the obiter lost contact, it was at an altitude of 110km. The Mars Obiter could only withstand the atmospheric pressure at an altitude of 80km. Thus, the spacecraft had exceeded an altitude of 30km and had disintegrated due to pressure. The flight system software on the Mars Obiter was using the metric system while the ground crew was entering course correction and thrusters data using the Imperial measure Pound-force . Thus, the ground crew and the computer had wrong calculations and thus let to the accident. The main error was the failure to use metric units in the coding of a ground software files. Thus, everything was instead converted in the imperial form and the altitude calculated was wrong. The ground crew should have been using metric statements instead of imperial. Thus, this incident could have been more avoided if they were given more metric training. Mars Climate Orbiter undergoing acoustic testing.

4. Timeline On September 23, 1999, during the Mars orbital insertion manoeuvre, Mars Climate Orbiter went out of radio contact when the spacecraft passed behind Mars at night 49 seconds earlier than expected, and communication was never re-established. On November 10, 1999, the Mars Climate Orbiter Mishap Investigation Board released a Phase I report, detailing the suspected issues encountered with the loss of the spacecraft. Previously, on September 8, 1999, Trajectory Correction Maneuver-4 was computed and then executed on September 15, 1999. It was intended to place the spacecraft at an optimal position for an orbital insertion manoeuvre than would bring the spacecraft around Mars at an altitude of 226-kilometers on September 23, 1999. However, during the week between TCM-4 and the orbital insertion manoeuvre, the navigation team indicated the altitude may be much lower than intended at 150-kilometers to 170-kilometers. Twenty-four hours prior to orbital insertion, calculations placed the orbiter at an altitude of 110-kilometers; 80-kilometers is the minimum altitude that Mars Climate Orbiter was thought to be capable of surviving during this manoeuvre. Final calculations placed the spacecraft in a trajectory that would have taken the orbiter within 57-kilometers of the surface where the spacecraft likely disintegrated because of atmospheric stresses. The primary cause of this discrepancy was human error. Specifically, the flight system software on the Mars Climate Orbiter was written to calculate thruster performance using the metric unit Newtons (N), while the ground crew was entering course correction and thruster data using the Imperial measure Pound-force. This error has since been known as the metric mix-up and has been carefully avoided in all missions since by NASA.

5. Conversion and calculation errors The dual usage of metric and imperial units can result in serious errors. These include: According to the National Transportation Safety Board, the confusion between pounds and kilograms means that aircraft are sometimes overloaded. The Institute for Safe Medication Practices has reported that confusion between grains and grams is sometimes the reason for medical errors. One example given is a case where a patient received Phenobarbital 0.5 grams instead of 0.5 grains (0.03 grams) after the prescriber misread the prescription. The Canadian "Gimli Glider" accident in 1983, when a Boeing 767 jet ran out of fuel in mid-flight because of two mistakes in figuring the fuel supply of Air Canada's first aircraft to use metric measurements,NASA's 1999 loss of the $125 million Mars Climate Orbiter because one engineering team used metric units while another used US customary units (Imperial system) for a calculation. Thus, I feel that the whole world should be using the metric system because the imperial system has caused dozens of accidents, including near fatal ones. It is just a matter of tie before another FATAL accident occurs. It Is better safe than sorry! America should really consider changing their imperial system to the metric one despite of the huge costs because lives are more important than money or cash. Adapted from : http://en.wikipedia.org/wiki/Mars_Climate_Orbiter

6. Videos on the Orbiter This is an animation of what exactly happened to the Mars Climate Orbiter. For my Gimli Glider project submission, there are also a few videos on YouTube which showcases exactly what happened on that fateful day. Thanks for watching 

7. Reflections I feel that this incident could be avoided and save NASA loads of money if not for the confusion in the imperial and metric system. For example, why didn’t NASA know that the computer in the Mars Orbiter was fitted with the metric system and instead asked its engineers to calculate using the imperial system?It was all because of human carelessness and error. The engineers were just too lazy to check and they were oblivious to any of the Orbiters machinery! If they had checked the computer systems in the first place, they would have found out the calculation mistake! Also, another problem was that NASA had not given its engineers any training at all! Why was the spacecraft fitted with the metric system and the engineers instructed to use the imperial system? All the fault lies on NASA’s shoulders. It did not check properly, neither did it caution its engineers and it did not learn from its mistake when two years ago, another orbiter also lost communication because of a human error during the set up! Also, I feel that NASA should not follow America’s imperial system and instead change all its systems to the metric one. Even if it really wants to stick to the imperial system, it must still ensure that its spaceships or Orbiters are fitted with the imperial systems calculations and not the metric one! Thus, I deeply regret the loss of this Mars Climate Orbiter as it was a saddening tragedy all because of human err! Never should it be repeated again! NASA should keep a checklist and caution its engineers in future!