Reminder from Mars: This is rocket science

Night after sleep-deprived night, NASA scientists crowded into tiny Room 225, the Mars Operation Center at NASA's Jet Propulsion Laboratory in Pasadena, Calif., and scanned the skies for overdue signals from the wayward Mars Polar Lander.

They munched the traditional NASA mission food - salted peanuts - and hoped for a sign. None came, and when the last meaningful chance for contact - and salvaging the mission - passed in the wee hours of Dec. 7, scientists were left to ponder the loss of two missions to Mars in the past 2-1/2 months.

Yet as designers begin the task of discovering what went wrong, some space scientists are saying that these recent episodes serve as an important reminder:

Yes, folks, this really is rocket science. And it isn't easy.

The art of running a space mission involves mind-numbingly complex calculations, affecting vehicles hundreds of millions of miles away, hurtling though space at 20 times the speed of sound. Missing an entry angle by one degree can mean three years of work will burn up in the atmosphere.

"It is very, very rare that everything works perfectly," says Ralph Kahn, a research scientist at the Jet Propulsion Laboratory. "You learn to work around things, to do the best you can with what you have."

The litany of failed Mars missions runs long. Russia, for instance, has yet to complete a Mars mission, despite more than a dozen efforts stretching back to the 1960s.

More technologically advanced and better-funded American missions have enjoyed a higher success rate, but the US has also lost its share, including the $1 billion Mars Observer in 1993, a major blow that spurred the agency's move to more numerous and cheaper missions.

But if NASA ever needed to nail a mission, the Mars Polar Lander was it. Still smarting from the September failure of the $120 million Mars Climate Orbiter - when engineers failed to make metric conversions - NASA has felt extraordinary pressure to successfully deploy the Polar Lander.

To ensure that the mission would come off cleanly, NASA beefed up efforts to check and evaluate everything about the Mars Polar Lander. This entailed going through millions of lines of computer code written for the mission - an area that many consider an Achilles' heel for NASA.

"Most of the cost of this mission is not in the physical hardware. It is in the testing and the checking," says Dr. Kahn. "The cost is primarily labor, and most of us work 70 or 80 hours a week to make these things work."

Until Friday, it looked as if their efforts had paid off. The passage from Earth to Mars appeared flawless. But the craft never reestablished contact after passing through the Martian atmosphere.

Any number of things could have gone wrong during the final 15-minute descent:

LIIf the lander's separation from the cruise vehicle that carried it and the two Deep Space 2 probes through space didn't happen just right, all three craft might have missed the planet or burned up.

*The lander had to slow from 15,000 m.p.h. to 5 m.p.h. using an aeroshell, a parachute, and a burst of rocket thrusters. The thin atmosphere on the pole made the task of braking the craft more difficult due to less resistance on the way down.

*The Deep Space 2 microprobes had to survive a 400 m.p.h. impact.

*The exact topography of the area near the south pole - where the lander touched down - is unknown. It could have lodged in a gully or on the edge of a hole. Or it could have fallen through a frozen crust on the surface and plunged into the soil.

Any of these scenarios could have presented problems for the Mars Polar Lander's primary antenna, which has an error tolerance of only 5 degrees. If the craft tilts even slightly, then data would broadcast uselessly in the wrong direction.

"It does take a fair amount of accuracy in pointing to get a signal," says Richard Cook, the project manager for the Mars mission.

Meanwhile, the tiny transmitters on the Deep Space 2 microprobes send out signals that are only a half watt in strength, barely enough to light a Christmas tree bulb. This made it nearly impossible for Earth-bound antennae to find the probes, which were to communicate through the Mars Global Surveyor.

"It's like trying to talk to someone with a cell phone on Mars," says Sarah Gavit, Deep Space 2 project manager, referring to her team's unlikely efforts to find signals using terrestrial listening devices.

Should the loss of the mission indeed prove total, NASA would suffer its first back-to-back failures in Mars exploration. Moreover, the loss of the lander would force the agency to rethink coming missions.

None of these mission are scheduled to go to the polar regions of Mars, where scientists say layers of sediment may hold critical evidence whether the Red Planet could have sustained life.

"We need to study those layers on the poles for the history of life and the history of the atmosphere," says Kahn.

(c) Copyright 1999. The Christian Science Publishing Society