NASA: Human error caused loss of Mars orbiter

The report also said the mission navigation team was overworked and not closely supervised by independent experts.

The panel made 10 different recommendations to ensure that a similar mishap is avoided with the Mars Polar Lander, currently en route for a December 10 touchdown on the red planet.

Artist's conception of the Polar Lander on Mars

Initially, NASA officials associated the failure with the agency's so-called "better-faster-cheaper" approach to unmanned space exploration -- a philosophy adopted in recent years that accepts a higher margin of risk in order to launch frequent missions at lower cost.

But NASA has since conceded that the failure was primarily the result of human error and that cost-cutting had little if anything to do with the fiasco.

The spacecraft was to be a key part of the exploration of the planet. From its position overhead, the Mars Climate Orbiter was to relay signals from the Mars Polar Lander once it reached the surface of the planet.

Signs of trouble came early

Months before the Climate Orbiter reached Mars, controllers at NASA's Jet Propulsion Laboratory saw signs of trouble but failed to understand the implications until it was too late.

"When the earlier trajectory work was being done it was noticed that the predictions ... were not as exquisitely accurate as they normally are," said mission controller Ben Clark of Lockheed Martin Aeronautics.

Such computer predictions are crucial because Earth-bound antennas offer controllers a one-dimensional and thus incomplete picture of where to find a spacecraft. But the discrepancies were so slight, the team simply discounted the predictions.

The Mars Climate Orbiter was equipped with one large solar array on one side, which was bombarded with millions of tiny solar particles as the spacecraft traveled to Mars. This solar "wind" tended to roll the spacecraft over.

A flywheel on board spun in the opposite direction to correct for the wind. Each day when it reset by spinning back the other way, tiny thrusters fired to counteract those forces.

Over a nine-month period, these small thruster activities gave the spacecraft more of a push off-course than controllers were able to track with their available data, said Richard Zurek, a project scientist for the mission.

Will Polar Lander be safe?

The prime contractor for the mission, Lockheed Martin, measured the thruster firings in pounds even though NASA had requested metric measurements. That sent the Climate Orbiter in too low, where the $125-million spacecraft burned up or broke apart in Mars' atmosphere.

That incident has prompted some 11th hour considerations about how to safely fly the Polar Lander.

"Everybody really wants to make sure that all the issues have been looked at," says Karen McBride, a member of the UCLA Mars Polar Lander science team.

The Polar Lander blasted off on January 3 from Cape Canaveral, Florida.

The spacecraft is designed to use a robotic arm to dig for water ice in the martian soil and conduct other science experiments in Mars' southern polar region

Correspondent Miles O'Brien and The Associated Press contributed to this report.