# This is the untold story of how NASA lost a Martian probe due to a miscalculation.

Pop quiz: convert 10 centimeters to inches. Easy, huh? Admit it, we all didn’t like math class. That awkward moment your math teacher asks such a question, and you’re like…, “does it even matter?” Why not use metrics as it is, and imperials as such. Simple, right? Here’s the catch: in 1999, engineers working at the National Aeronautics and Space Administration (NASA) made a terrible calculation error on one of their satellites, they forgot to convert metric units into imperial units, and failed an entire Mars mission. Like what?

### Once Upon A Mistake

The story unfolded in the fall of 1999, when NASA’s 125-million-dollar Mars Climate Orbiter (MCO) — the first weather observer on another planet lost its signal. The orbiter was supposed to have reached its destination and in a stable orbit, but scientist realized that it had vanished, and was gone for good. Disaster investigators reported that the orbiter had burned up in the Martian atmosphere because of a technical error.

“It was pretty clear that morning, within half an hour, that the spacecraft had more or less hit the top of the atmosphere and burned up,” recounted NASA engineer Richard Cook, then project manager for Martian explorations at the time.

It was later confirmed to be a failure to convert metric units to imperial units by software engineers. A NASA review board found that the problem was a miscalculation in the software controllers of the orbiter’s thrusters. The software did calculate the force the thrusters needed with imperial units (pounds), whereas another software also took in that data assuming it was in metric units(newtons). There were several warning signs, according to the review board.

En route to Mars, the orbiter had to make 10 to 14 times more minor adjustments than the engineers expected. It was slightly dipping into the Martian atmosphere — about 169 kilometers (105 miles) lower than expected.

### The Metrics Vs Imperial Problem

Consequently, the orbiter was within 60 kilometers (37 miles) of the Martian surface, and simulations showed that, at any altitude lower than 85 kilometers (53 miles), the orbiter was at risk of the atmosphere tearing it apart. The whole deal was ruled as a miscommunication error by propulsion engineers at the Lockheed Martin Center who built the craft — who typically expressed force in pounds — but this was standard practice to re-check and convert to newtons for space missions.

So engineers at NASA’s Jet Propulsion Lab (JPL) thought the conversion was made, and didn’t re-check. And, lo and behold, disaster did strike. According to Cook, there was an underlying issue in the culture of NASA’s space exploration at the time. And on September 21, The New York Times published a preview article captioned ’Beginning a Bargain-Basement Invasion of Mars,’foreshadowing the disaster awaiting to happen.

The Mars Climate Orbiter wasn’t NASA’s only Martian probe casualty, 23 days later, the Mars Polar Lander (MPL) also disappeared on it’s way to the Red Planet due to vibrations in it’s landing gear, which was roughly 30.5 meters (100 feet) in the air, when miscalculations in the software led it to a crash landing.

“‘Better, faster, cheaper’ was the mantra at the time,” Cook said. “Certainly that project was trying to do a whole lot for a limited amount of money.” And ”the specific reasons [for that failure] were totally different, but the underlying part[s], this overly ambitious appetite, were the same,” he added.

### You Better Check, And Re-check

According to Cook, NASA made some “big-time” amendments afterwards, obviously. This included several planned missions like the … that was supposed to bring back rock samples back to Earth, but were scrapped. NASA went back to basics, rebuilding Mars programs based on well-tested concepts and conservative strategies. And this was a success.

Popular of these missions were the Mars Exploration Rovers — talking of Curiosity, Spirit, and Opportunity — which made dreams of Martian Sci-Fi movies a reality. These rovers, not only did they land on the Red Planet and completed their 90-day missions, they were (and are still) trekking on Mars years later.

“The units thing has become the lore, the example in every kid’s textbook from that point on,” Cook said. “Everyone was amazed we didn’t catch it.”

Source: NASA