July 4 a Red-Letter Day for Mars Probe

Donna Shirley, manager of NASA’s Mars program, idly tosses a paper airplane into the sky and watches it loop about in the breezes of Dabney Courtyard at Caltech--no doubt wishing that the landing will be as easy July 4, when NASA’s pint-size Pathfinder spacecraft arrives on the surface of Mars.

As the first emissary from Earth to the planet next door in more than two decades, Pathfinder is poised for a perilous--and spectacular--drop to the Martian surface. “It’s going to be better than New Year’s Eve,” said Shirley.

Someone sitting on Mars this Independence Day would look into the predawn darkness to see a shooting star streak by. Then darkness would return for a few silent minutes before “all hell breaks loose,” said Tony Spear, project manager for the mission at the Jet Propulsion Laboratory in Pasadena.

A parachute will sprout from the spacecraft’s back to slow its descent. Retrorockets will fire, bringing it to a halt about 50 feet above the planet’s surface. Then, poof! Enormous balloons will inflate explosively, encasing the whole lander in a cocoon.

Seconds before touchdown, the connection to the parachute will be cut, liberating the balloon-clad lander to fall toward the rocky surface below, bouncing like a superball--maybe 10 stories high--before rolling to a stop.

When the red dust settles, Pathfinder will open its petals to reveal its VIP cargo, a six-wheel-drive dune buggy named Sojourner that will stand up to its full 1-foot height, then descend a runway like Miss Universe herself into the red Martian dawn.

“Won’t that be something?” Spear said. “God, I would love to be there. I think about that all the time.”

In fact, the entire second floor of the Space Flight Operations Center at JPL has a bad case of preflight jitters. A giant backlighted clock counts down the days, hours, minutes and seconds to Pathfinder’s arrival. “It’s the scariest thing I’ve had to deal with in my life,” said Spear. MARS OR BUST signs are everywhere, along with wishes from schoolchildren and fellow scientists.

If past experience is any guide, the probability of success is not great. NASA’s billion-dollar Mars Observer disappeared near the Red Planet in 1993, and Russia’s Mars96 is believed to have crashed in Bolivia. Corpses of failed Russian landers litter the planet’s surface. And engineers joke that the Great Galactic Ghoul lurks near the fourth planet from the sun, waiting to gobble up uninvited visitors.

“People don’t realize that it’s very, very hard to land on another planet,” Shirley said.

But the stakes couldn’t be higher. Ever since NASA researchers found possible evidence of fossil life on a Martian meteorite last summer, getting to Mars has acquired a special urgency. “The larger theme is not Mars,” says Planetary Society President Bruce Murray. “It’s that four-letter word spelled L-I-F-E.”

Mars History Could Offer Clues to Earth

Like any close relative, Mars has a lot to tell us about our own history. The rocks that bear the earliest record of Earth’s past have long since been plowed under the surface by shifting continental plates, cooked and mixed into unrecognizable forms and churned about by ice ages and volcanoes. On the relatively still surface of Mars, however, such record-bearing rocks lie about the surface, “just waiting to be picked up by a small rover,” said Dan McCleese, program scientist for the Mars Surveyor program.

These rocks might well hold clues to how life got started here and how our planetary home might evolve in the future. Mars was once a watery blue marble in space, much like Earth. No one knows what happened to its atmosphere, its lakes and rivers. “Mars is a laboratory in the sky for studying climate change,” McCleese said.

Mars also has a mystical pull that’s given it a starring role in countless science fiction sagas. “Mars is special,” said NASA chief Daniel Goldin. “It gets to everybody’s heart and soul. I’m going to be out there watching it with my grandson.”

NASA is mining that mystique. The Independence Day landing was determined in part by the close alignment of the planets during early July. “We could have landed on the third or fifth,” said McCleese, but the fourth was chosen primarily in tribute to the successful Viking mission to Mars 21 years ago.

On July 4, 1976, Viking was to have settled into the permanent sunset of the Martian sky to celebrate the nation’s 200th birthday. Alas, a dust storm blew away those well-laid plans, and the lander was deterred for several weeks while the weather cleared.

No such storms seem to be in store for Pathfinder, however. Both the Hubble Space Telescope and scores of amateur astronomers are keeping an eye on the planet, and so far, the weather looks good--clear and cold.

In any event, Pathfinder couldn’t do much to avoid a storm. Unlike the Viking landers, which rode to Mars aboard orbiters, then circled the planet waiting for the weather to clear, Pathfinder has been thrown at the Red Planet like a rock, on a direct, straight-line trajectory. “We’re going to hit the planet no matter what,” Shirley said.

The risks are high, but that’s the point--to test bold new technologies for getting to Mars cheaply and quickly. This is the first time, Spear said, that a spacecraft has ever taken itself to Mars rather than being chauffeured into Mars orbit by a mother ship, then dropped gently to the surface. Pathfinder is a lone explorer. “It’s in charge,” Spear said. “It’s got the brains.”

Hurtling toward Mars at more than 17,000 mph, Pathfinder will tear into the thin Martian atmosphere, heat shield first. Within minutes, friction will have slowed the craft to about 900 mph.

The parachute opens, the heat shield gets dumped, and Pathfinder descends. Mere seconds from the surface, the rockets flash briefly, the balloons, or air bags, inflate and Pathfinder hits the surface at about 20 mph. It could bounce and skid for 10 minutes or more before settling down. Designed like a flak jacket with four layers of bulletproof-vest material, the balloons should take whatever punishment Mars serves up.

It’s all over in five minutes--assuming everything goes precisely as planned. “A hundred things have to happen, and they all have to happen right,” said Matthew Golombek, Pathfinder project scientist. A slight malfunction anywhere in the chain of events could send Pathfinder crashing to a dusty death. “We’re all going to be standing by, worrying like crazy,” Golombek said.

The landing site--an ancient flood plain called Ares Vallis--was chosen largely for safety reasons. “If you crash and burn, nobody gets any science done,” said Golombek. The terrain had to be low, providing enough of an atmospheric cushion to brake the craft. It had to be flat to reflect radar signals required for safe landing. It had to be sunny enough to feed the lander’s solar panels.

Engineers are aiming for an enormous 60-by-120-mile oval, as big as the entire area from Santa Barbara to Orange County. But the smallest detail they can see--even with close-ups from Viking--is larger than a football field. “There’s a tremendous amount we can’t see,” Golombek said. “I have no idea what the landing site’s going to look like [close up].”

Chosen also for its geological interest, the site contains a grab bag of rocks, ranging from relatively young volcanic specimens to ancient rocks dating back to the origins of the solar system--4.5 billion years. Those ancient rocks are similar to the now famous meteorite containing possible evidence of ancient life. Researchers hope that the story of the dawning of life may be locked inside.

The wheel-less Viking landers of 1976 found no signs of life, but they were stuck where they landed, and any interesting rocks beyond arm’s length were simply out of reach. In contrast, Sojourner--named after Civil War-era reformer Sojourner Truth--rolls around on six wheels that operate independently. It can look ahead for obstacles with laser sensors, and it turns on a dime. If it bumps into something, it has the ability to back away.

Sandbox a Practice Field for Rover

For the last seven months, the little Sojourner has been scrunched down to 7 inches for its trip to Mars. Meanwhile, its exact duplicate at JPL--named Marie Curie--has been putting in long hours in the faux Martian “sandbox,” rehearsing every move that Sojourner will make.

Based on lessons learned from testing Marie, controllers last week sent a command to wake the sleeping robot and install new software, Shirley said.

At 120 million miles from Earth, the rover has to be a smart operator. Because it takes more than 10 minutes for a signal to travel from Earth to Mars even at light speed, a warning from JPL controllers to watch out, say, for a looming cliff would arrive too late to do any good.

Engineers at JPL wear 3-D goggles that allow them to view Sojourner’s relayed images of the Martian landscape and direct the rover to various sites. But Sojourner must navigate on its own. More than 100 scientists from all over the globe have descended on JPL, getting ready to retrieve and make sense of the two to three hours’ a day worth of data they expect to pull down from the lander and its roving companion.

Sojourner carries a sophisticated instrument that can reach out to a rock like an elephant’s trunk, shooting subatomic particles at a small patch and analyzing what bounces back to obtain the atomic number, and therefore the identity, of elements in the rock.

“It does what a geologist in the field does,” Golombek said, including taking 3-D pictures. By looking at a rock, he said, any trained geologist can tell when, how and where it was formed--clues to the planet’s history.

At just over $250 million, the entire mission is a radical departure for NASA, says former JPL chief Murray. By comparison, the Viking missions cost about $3.6 billion in today’s dollars. “Cost was no object in Viking,” said Golombek. Pathfinder, in contrast, was a fixed-price mission. In fact, the JPL team actually returned $7.07 of its budget, Spear said.

The pared-down budget was achieved largely through cheap commercial technology. The rover communicates with the lander, for example, using off-the-shelf (though modified) Motorola radios, Shirley said.

It was also part of NASA chief Goldin’s mandate of fast, cheap and focused missions. No more spacecraft decorated like Christmas trees with decades’ worth of experiments. Instead, JPL is planning to send a total of 10 small spacecraft to Mars over the next 10 years to test new technologies, bring back rocks and scout likely landing sites for future missions.

Goldin, said Murray, gave planetary exploration a focus: Mars. “Dan Goldin does not believe all planets are created equal,” Murray said. “The dust ring around Jupiter is interesting, but it’s not the same.”

Only Mars (and possibly Jupiter’s icy moon, Europa) seem possible harbors for life. “This is an agency that’s trying to see if life is unique to this planet,” Goldin said.

“This is the frontier,” Shirley said. “We’re Lewis and Clark, and we don’t quite know what we’re getting into. When we get through the first expedition, we’re going to come back and tell the next expedition to carry better weapons or more food. That’s how we’re going to build this up.”

Eventually, she said, “we’ll send the settlers in covered wagons.” Any human missions, agreed Goldin, will have to learn to live off the land--just like the early pioneers on planet Earth.

In the meantime, there will be plenty of nervous waiting. Although Pathfinder is due to land on Mars at 10 a.m. Pacific time Friday, “it isn’t expected to signal that all is well until 1:30 that afternoon,” Golombek said. “That’s 3 1/2 hours of an awful lot of worry.”

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Mission to Mars

On Friday, July 4th, NASA’s Pathfinder spacecraft is due to plunge into the thin red Martian sky, the first U.S. visitor to the planet next door since the Viking missions 21 years ago. Primarily intended to test untried-technologies for landing on Mars cheaply, the mission will also road test a semi-intelligent rover and determine the elements present in the Martian soil.

PATHFINDER LANDER

Designed to open its petals like a flower when it settles on the Martian surface the lander serves as life support for the rover. It takes pictures with stereo cameras, handles communications between the rover and Earth, and takes weather readings, including wind speed, temperature and pressure during descent and throughout the mission.

ROVING VEHICLE

The six-wheeled traveling science laboratory of dune buggy design needs to navigate on its own, since communications to Earth take too long--about 10 minutes. Lasershelp the Sojourner spot obstacles and divert around them. The loosely jointed design allows it to climb over boulders without tipping.

The Sojourner, named after Civil-War-era reformer Sojourner Truth, also carries two stereo cameras for close inspection of rocks and sophisticated instrument called an Alpha Proton X-Ray Spectrometer that allows it to detect elements in the Martian rocks.

ENTRY, DESCENT AND LANDING

Coming in from space with a speed of about 17,000 miles per hour, Pathfinder has to slow down dramatically before landing softly on the Martian surface. The heat shield burns up in the thin C02 atmosphere getting rid of about 98% of the energy put into the spacecraft at launch. Throughout the landing, the spacecraft is under its own control--the first time a craft has ever landed itself on Mars without the help of an orbiting “mother ship”.

1. Cruise Stage Separation: The cruise stage is then jettisoned from the entry vehicle about one- half hour before landing.

2. Entry: An aeroshell (including the heat shield) protects the lander from the intense heat of entry.

3. Parachute Deployment: A 24-ft. diameter parachute is deployed after 2-3 minutes.

4. Heat Shield Separation: Small explosives separate heat shield from lander.

5. Lander Separation/ Bridle Deployment: The lander is lowered into position at the end of the bridle made of Kevlar.

6. Radar Ground Aquisition: The lander’s radar altimeter is expected to locate the surface about 32 seconds before landing.

7. Airbag Inflation: Airbags are inflated above the surface about 8 seconds before landing.

8. Rocket Ignition: Rockets bring the lander to a halt 13 yards above the surface.

9. Bridle Cut: A cutter releases the bridle thereby freeing the back shell from the lander. The rockets launch the back shell up and away taking the parachute with it.

10. Landing: Airbags made of high-strength fiber called Vectran encase the lander as it falls, bouncing on the surface.

11. Once the lander comes to a standstill on the surface, small winches on each of the lander sides retract the airbags. Vents are forced open on the side of each bag.

12. Should the lander come to rest on its side, it will be righted by a motor on each of the three panel hinges.

13. About 3 hours is allotted to retract the airbags and deploy the lander solar panels. After 3.5 hours, the lander will be fully operational. Ramps then extend from one of the panels, from which the rover will drive out.

Sources: Jet Propulsion Laboratory, Pasadena, California

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Mars Pathfinder

The Pathfinder spacecraft above, is scheduled to complete a seven-month journey Friday when it touches down on the surface of Mars.

Earth at launch Dec.2, 1996

Mars at arrival July 4, 1997

Note: 30 day increments

Source: Jet Propulsion Laboratory in Pasadena

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Where to Find Mars on TV

Working with the Jet Propulsion Laboratory, KLCS-TV Channel 58 will offer 6 1/2 hours of live programming Friday pegged to the spacecraft Pathfinder landing on Mars.

The coverage, beginning at noon, will originate from the Planetfest ’97 conference in Pasadena and will feature the first pictures of Mars as they are beamed back from outer space.

KLCS is a public-TV station operated by the Los Angeles Unified School District.

Other TV news outlets will be covering developments during the day Friday. In addition, CNN will air a half-hour special at 7:30 p.m.,”Journey to the Red Planet,” and the Discovery Channel plans an hourlong report a 8 p.m., “Mars Live.”