Two Teams, Two Measures Equaled One Lost Spacecraft

October 1, 1999
By ANDREW POLLACK

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LOS ANGELES -- Simple confusion over whether measurements were metric or not led to the loss of a $125 million spacecraft last week as it approached Mars, the National Aeronautics and Space Administration said on Thursday.

An internal review team at NASA's Jet Propulsion Laboratory said in a preliminary conclusion that engineers at Lockheed Martin Corporation, which had built the spacecraft, specified certain measurements about the spacecraft's thrust in pounds, an English unit, but that NASA scientists thought the information was in the metric measurement of newtons.

The resulting miscalculation, undetected for months as the craft was designed, built and launched, meant the craft, the Mars Climate Orbiter, was off course by about 60 miles as it approached Mars.

"This is going to be the cautionary tale that is going to be embedded into introductions to the metric system in elementary school and high school and college physics till the end of time," said John Pike, director of space policy at the Federation of American Scientists in Washington.

Lockheed's reaction was equally blunt.

"The reaction is disbelief," said Noel Hinners, vice president for flight systems at Lockheed Martin Astronautics in Denver, Colo. "It can't be something that simple that could cause this to happen."

The finding was a major embarrassment for NASA, which said it was investigating how such a basic error could have gone through a mission's checks and balances.

"The real issue is not that the data was wrong," said Edward C. Stone, the director of the Jet Propulsion Laboratory in Pasadena, Calif., which was in charge of the mission. "The real issue is that our process did not realize there was this discrepancy and correct for it."

Some experts also wondered how something so basic could have gone undetected so long.

"Last time I checked I could sort of visually detect the difference between a foot and a meter," Pike said.

"This is kind of the very first thing in Physics 101 or Engineering 101. This is the only significant program failure that anyone's ever heard of that's due to this."

The failure could raise questions about whether NASA and its contractors are skimping on safety in order to cut costs. The Mars Climate Orbiter, the first spacecraft designed to study the climate of another planet, was exceedingly inexpensive by NASA's standards. It is part of a new strategy to fly more but less expensive, missions to Mars.

That limits the damage done by the failure of any single mission. "There is not a single mission in the program that is critical to the overall program," said Stone, the Jet Propulsion Laboratory director.

But Pike said "Obviously the question they are going to have to ask is maybe it was a little too cheap. The question that will have to be asked here is whether in cutting costs, they cut corners."

The failure is also another black eye for Lockheed, the nation's largest military contractor, which in the last year or so has suffered several failures of rockets and missiles it has developed. These failures led the company to restructure its operations and change management in its space business.

NASA officials said they are checking to make sure the same error does not occur in the Mars Polar Lander, which is now en route to Mars and scheduled to reach the planet on Dec. 3.

Two separate review committees have already been formed to investigate the loss of the Mars Climate Orbiter -- the internal Jet Propulsion Laboratory peer review team, which made today's preliminary findings, and a special review board of experts from the laboratory and elsewhere.

An independent NASA failure review board will be formed shortly.

It is not known with certainty what happened to the Mars Climate Orbiter. At first there was speculation that it crashed on Mars or burned up in the atmosphere.

But the review team now tends to think that the spacecraft might have never left Mars' orbit and is now orbiting the sun, a Jet Propulsion Laboratory spokesman said. Under this theory, the spacecraft approached too close to Mars and got to hot, causing the engine that was burning to bring the craft into orbit to stop functioning, so the Orbiter went back into space.

NASA and Lockheed officials said the full details of how the mistake occurred are not known. But, basically, Lockheed was providing the Jet Propulsion Laboratory with data on the amount of energy imparted to the spacecraft by its thrusters that are fired periodically. This was measured in pound-seconds, Hinners said.

But scientists at the Jet Propulsion Laboratory assumed the figure was in newton-seconds and incorporated it into computer models that are used to calculate the spacecraft's position and direction. These models supplement other data about the spacecraft's position, Stone said.

Since one pound equals about 4.4 newtons, it would seem that such an error would be readily detected, but Hinners said this was not the case because the thrusters contributed only a little to the orbit. "The firings would have been a very small piece of a larger number," he said.

The miscalculations put the spacecraft off course by only about 60 miles out of a journey of roughly 416 million miles, Stone said.