DATE: Friday, July 4, 1997                  TAG: 9707040542

SECTION: BUSINESS                PAGE: D1   EDITION: FINAL 

SOURCE: BY AKWELI PARKER, STAFF WRITER 

                                            LENGTH:   89 lines

SCIENTISTS WAIT FOR SUCCESSFUL LANDING

Just before 1 p.m. today, the Mars Pathfinder probe is expected to hurtle into the Martian atmosphere, paving the way for a series of exploratory flights to the Red Planet into the next century.

Until it touches down, a group of scientists from NASA Langley Research Center will be holding their collective breath.

In a sense, the rest of Pathfinder's mission - exploring the Martian surface and reporting back to Earth by radio - rides on whether or not those engineers did their math correctly.

``We put all these thermodynamics together . . . based on fundamentals of chemistry and physics,'' says Robert Mitcheltree, an aerospace engineer with NASA's aerothermodynamics branch at NASA Langley.

About three years ago, Mitcheltree and about a half-dozen others began figuring out how to get Pathfinder from a point in space above Mars into the planet's atmosphere, without getting the high-tech laboratory broken or fried in the process.

If it comes in too steeply, the craft won't have time to perform a complex series of pre-landing tasks. Also, the high speed of a steep entry could burn up the module.

If Pathfinder approaches Mars at too shallow an angle, it will bounce off the atmosphere - like a stone skipping a pond - and be forever lost in space.

Other teams were charged with getting Pathfinder to Mars, landing it and designing the six-wheeled Sojourner rover that will explore the planet.

The stakes are much higher than the Pathfinder hardware's $280 million price tag: NASA desperately needs a slam-dunk success.

With last week's near-catastrophe on the Russian space station Mir and NASA's budget on the congressional equivalent of a Slim Fast diet, space exploration these days is requiring increasing validation from legislators and taxpayers.

Like post-Cold War Russia's shriveled space program, the National Aeronautics and Space Administration has had a string of troubles this decade.

In 1993, for instance, the $1 billion Mars Observer got lost in space along with seven scientific experiments.

``Space is risky - it's complicated,'' said Henry Hertzfeld, a senior research scientist with George Washington University's Space Policy Institute. ``You're not sending up something like your automobile.''

But Mars, with its proximity and relatively Earth-like climate, remains a tantalizing prospect to scientists and futurists.

Probes are expected to stake out the planet through 2005, with the possibility of a manned mission by 2014.

The unmanned missions will serve to confirm or refute NASA scientists' calculations on everything from the seven-month cruise there to actual surface conditions. The trips will build on information gleaned from the successful Viking missions to Mars in the mid-1970s and even re-examine the possibility of life there.

Precision is key to the Pathfinder mission - getting the module from Earth to the correct entry window above Mars is mathematically akin to hitting a golf ball from Pasadena, Calif., to a hole in Atlanta.

NASA Langley scientists had the help of powerful Cray supercomputers and Silicon Graphics workstations (made famous by the digital dinosaurs of Jurassic Park) in completing their tasks.

Among other things, they designed and tested the shape of Pathfinder's entry module. They also predicted how it and its Viking-derived heat shield would react when heated to thousands of degrees upon hitting Mars' thin atmosphere.

``It's very exciting to have worked five years on a mission developing computer tools from which we'll get flight data,'' says Mitcheltree.

He and possibly millions of others will be on the edge of their seats as reports on Pathfinder's progress come back via NASA officials, World Wide Web sites and the ubiquitous CNN.

Teammate Robert Braun will be at Pathfinder mission control at NASA's Jet Propulsion Laboratory in California, overseeing the entry phase of the mission.

By Monday, the NASA-Langley team will be poring over the flight data sent back from Mars, analyzing it, comparing it to their predictions and eventually applying it to future missions.

Although their work means the difference between receiving mountains of valuable data and the voyage ending in a brilliant fireball, Mitcheltree is self-effacing about his team's role.

Says Mitchelltree, ``What we do at Langley is just a piece of this mission.'' ILLUSTRATION: LAWRENCE JACKSON/The Virginian-Pilot

ARRIVAL ON THE RED PLANET Dr. Robert A. Mitcheltree, who's with the

aerothermodynamics branch at NASA Langley, holds the forebody shape

of Pathfinder, which is scheduled to land on Mars today. By Monday,

scientists at Langley will be poring over data sent back by the

project.

Color graphic by JOHN CORBITT, The Virginian-Pilot

Atmospheric entry: Shuttle vs. Pathfinder