NEXT STOP: RED PLANET; MARS MISSION RIGHT ON TIME, SCIENTISTS SAY.

Byline: Tony Knight Daily News Staff Writer

Streaking toward the Red Planet at 12,000 mph, NASA's Mars Pathfinder space probe is right on target for an Independence Day landing, mission scientists said Tuesday.

``It looks like we're going right down the middle of the barrel for entry,'' mission manager Richard Cook told an assemblage of the world's press that has convened at Pasadena's Jet Propulsion Laboratory for the interplanetary encounter.

Launched Dec. 4, the 3-foot-tall spacecraft has hurtled through millions of miles of space for its historic rendezvous with Mars.

Mission control is at the JPL's famed Arroyo Seco campus. Designed and largely built by JPL engineers and scientists, this is one of the first of the National Aeronautics and Space Administration's ``smaller, faster, cheaper'' Discovery missions.

It also is the first American mission to the Martian surface since 1976, when two Viking landers sent back the first-ever pictures from the surface of another planet.

If all goes as planned, new pictures from the Red Planet will be available to the earthbound public by about 6 p.m. Friday.

Pathfinder also will deploy a 23-pound rover, equipped with cameras and other sensors, to explore several hundred yards of Martian real estate over the next 60 days. The rover has been named Sojourner after American civil rights crusader Sojourner Truth.

But first, the spacecraft will have to plunge into the thin Martian atmosphere at more than 16,000 mph and survive 2,000-degree heat before deploying a parachute at twice the speed of sound.

``This is a very hot entry,'' said Brian Muirhead, deputy project manager.

Then comes the really risky part. Slowed to a mere 120 mph, the space pod will inflate three giant air bags, enveloping itself in a protective cocoon. Retrorockets will fire, stopping the descent at about 100 feet, and the $171 million spacecraft will drop the rest of the way to the surface.

The first bounce could be as high as a 10-story building. But Pathfinder is supposed to be able to take the punishment as it bounces and rolls around the Martian surface before coming to a stop in the flat, sandy reaches of Mars' Ares Vallis region.

``The air bags are the things we're most concerned about,'' Muirhead said. ``That's the biggest uncertainty. We don't know the nature of the terrain on which we're going to be landing.''

At the first of what is planned as a series of news briefings leading up to the landing and the first days of the mission, JPL scientists said they are getting the jitters as the crucial entry-and-descent phase approaches. But they said they are confident because the spacecraft's hardware has performed flawlessly during its seven-month journey.

Pathfinder will land shortly before 10 a.m. Friday. Within minutes, JPL scientists should receive a signal confirming that the landing was a success.

But it won't be until 3 p.m. Pacific time, a little over an hour after the sun rises over the Ares Vallis site, that the first data is received confirming that the spacecraft is healthy and in reasonably good condition.

If the lander's high-gain antenna is working, the first pictures from Mars should be received on Earth at about 6 p.m., and NASA will continue to release images throughout the evening, as the rover is deployed to the Martian surface.

CAPTION(S):

2 Photos

PHOTO (1) Brian Cooper will use special glasses to drive Pathfinder's rover from his JPL computer in Pasadena.

(2) Full-scale reproductions of Pathfinder, background, and its rover are shown.

Hans Gutknecht/Daily News