September 18, 1995 in City

Prof’s Life’s Work Rides On Spaceship

Eric Sorensen Staff writer

It will take 54 tension-filled minutes for David Atkinson to find out if 15 years of his life’s work will bear fruit.

It will begin in early December as a probe from the spaceship Galileo pierces Jupiter’s atmosphere at 106,000 miles an hour. In just one minute, most of the probe’s heat shield will be evaporated by an incandescent shock wave nearly twice as hot as the surface of the sun. Approaching 350 Gs, the 750-pound probe will assume the weight of a DC-10.

A minute later, after a Dacron parachute opens and the heat shield drops off, the probe will begin to take the first direct measurements of the Jovian atmosphere. It will take another 52 minutes for those measurements to travel 600 million miles to Earth.

Only then will Atkinson have an inkling that his experiment, one of only eight on the $250 million probe, is working.

If engineers of the effort are questioning whether it’s all worth it, they aren’t letting on.

“This is data we’re never going to get again,” said Marcie Smith, the probe project manager, as she visited from NASA’s Ames Research Center to give a research colloquium Tuesday. “I think it’s invaluable.”

Because Jupiter is so massive, holding two-thirds of all the solar system’s matter outside the sun, it is likely to have elements in proportion to the original solar nebula. That makes it the ideal laboratory of the cosmos.

“It’s like a time capsule,” Atkinson said. “Where the solar system was formed 4 or 5 billion years ago, you have one planet that is essentially what the solar system was made of.”

The more scientists like Atkinson can learn about Jupiter, the more they might learn about the formation of the solar system - and life itself.

Since Galileo Galilei first saw Jupiter nearly 400 years ago, science has had only a passing aquaintance with the great planet. By breaking down its light waves, scientists have deduced the gases of the planet’s atmosphere. Radio waves sent by the passing Pioneer and Voyager spacecrafts in the 1970s provided more information about the atmosphere’s intense temperatures and pressures.

By comparison, the Galileo probe’s experiments will look at the the atmosphere’s temperature, pressure and density, the gases at varying altitudes, the ratio of hydrogen to helium, the location of the cloud layer and its particles, the atmosphere’s energy flux, and lightning and radio emissions in the planet’s radiation belts.

For Galileo engineers, it will be the end of a six-year journey, not counting the delays brought about by the Challenger disaster and engineering concerns raised by each new launch date.

For Atkinson, 39, it will be a milestone in 15 years of work, including a stint at the Ames Research Center and a Ph.D. program in electrical engineering at Washington State University. By the time the spaceship was launched in 1989, Atkinson had already been a University of Idaho professor for two months.

Come Dec. 7, Atkinson aims to start determining the different wind speeds in the Jovian atmosphere by analyzing the rate at which radio signals change while the probe is hurled crosswise during its descent. The speeds are key to gauging the energy balance in the atmosphere - whether it comes from the sun or energy in the planet itself.

It is a dicey proposition.

If the probe entry is off by one degree, his measurements can be thrown askew.

If the probe’s batteries don’t work - engineers can’t test them without draining them - the probe can vanish as mysteriously as the ill-fated Mars Observer.

Already, problems with the main spacecraft’s antenna have forced engineers to rethink how they will receive signals from the probe.

When they do, it will be at a rate of 128 bits per second, a fraction of the rate sent by the typical desktop computer modem.

By the time Atkinson first fields that data, the bulk of the probe’s descent will be over. The probe will be in a zone of clear, hot hydrogen. It will be in a pressure cooker, with a temperature rising above 200 degrees Fahrenheit and air pressure 30 times as great as on Earth.

One hour and 15 minutes after entry, the probe will be incapacitated and well on its way to a meltdown.

And if all goes well, Atkinson will have his life’s data.

, DataTimes ILLUSTRATION: Graphic: Probing Jupiter’s secrets

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