Gadgets Allow Mars Lander to See, Hear

When the Mars Pathfinder spacecraft arrives at the Red Planet on Friday morning, it will do what any other tourist in a strange land would do: look around.

First, it will take in the panoramic view to make sure the coast is clear of boulders and other obstacles; then it will look up into the sky and check the weather; then it will sniff the air.

If all looks well, “We’ll [roll out] the rover and go exploring,” said science team chief John Wellman at a news briefing at the Jet Propulsion Laboratory in Pasadena on Wednesday.

In preparation for the Friday landing, scientists reviewed the cleverly constructed eyes, ears, nose and fingers that the spacecraft will use to get a good sense of this unexplored territory. They will also be on the lookout for illusions that can easily be produced when the human mind meets ambiguous data.

“The human imagination can run wild,” said Peter Smith, principal scientist on the Imaginer for Mars Pathfinder, the main camera that will be sending pictures back to Earth. He warned against mistaking distortions in the images for Martian life.

When the first Viking lander reached Mars 21 years ago, it saw a big rock that looked very much like an enormous toad, said rover scientist Henry Moore. “We even named it Mr. Toad.”

Viking also sent back pictures of a blue Martian sky much like Earth’s. But when the color was properly tuned, the sky turned out to be pink. This time, researchers are ready not only for a pink Martian sky, but also for a possible blue sunset. Just as the Earth’s air scatters blue light, leaving only red left at the end of the day, Mars’ dusty red atmosphere is expected to do the opposite.

The fact that Viking researchers first interpreted the Martian sky as blue is an example of the kind of “projecting that’s going on in your mind,” said Smith--seeing what you expect to see, instead of what’s really there. “You look at these pictures on a computer and then you have to imagine what the object is really like on Mars.”

Each night, said Smith, whose home base is the University of Arizona, he has been looking from his hotel window in Glendale and seeing Mars hanging in the western sky. In less than 48 hours, his IMP stereo camera will be “looking back at us.”

While Earth will appear to the camera only as a small blue dot in the Martian night sky, closer environments should come into sharp focus.

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The camera’s 10-pound “head” sits atop a five-foot flexible wire skeleton that’s traveling to Mars coiled up in a kind of tin can. But once Pathfinder lands, it will spring up like a jack-in-the-box to get a view.

With two wide eyes set twice as far apart as human eyes, IMP can take three-dimensional pictures in 12 colors. Its “neck” swivels 360 degrees like something out of “The Exorcist,” and it can look straight up at the sky, or straight down.

The camera will peer up at the sun to measure the amount of dust in the Martian sky; it will look straight down only during a dust storm to shade its eyes. It even has metal “eyebrows” built in for that purpose.

The human appearance of the robot is enhanced by a tiny smile made of air vents that was etched on its face by an engineer at Lockheed Martin with an impish streak.

Because IMP takes one frame at a time and then pieces them together, black “tiling” marks may appear in some images, as well as waffling and geometrical distortions. Although it is scheduled to begin transmitting pictures Friday, its first movies--scheduled to be beamed to Earth by Saturday--will be only nine frames long.

In addition to “eyes,” Pathfinder carries several sets of sensors much like the natural ones in the human ear that help people tell whether they’re accelerating in a roller coaster, or spinning around or standing on their head. These “accelerometers” will help orient the spacecraft and sense changes in gravity and pressure.

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The spacecraft also carries a complete weather station, with 3-inch gossamer metal windsocks fluttering from three heights on a pop-up mast, along with temperature, pressure and wind-speed sensors. The speed of the wind is calculated by its cooling effect on tiny wires facing six directions--and the extreme delicacy of these wires is a worry during Pathfinder’s rough landing, said JPL’s Tim Schofield, the science team leader on the instrument.

Pathfinder’s roving sidekick--the six-wheeled robot named Sojourner--also carries its own stereo “eyes” (cameras) that will send back pictures, as well as a sensitive “nose” that can sniff elements in the soil and rocks. Its electronic proboscis will be on the lookout for evidence that water once flowed on the now-dry planet; for example, if the soil has a much higher sodium content than surrounding rocks, that could indicate that water washed salt out of the rocks and deposited it in the dirt, just as it does on Earth.

Looking at the relative balance of different chemical elements should also prove whether meteorites thought to have traveled from Mars to Earth--like the one bearing structures that look like fossil life--are truly from Mars.

Receivers will also listen to radio signals between Earth and Pathfinder to obtain information about the way Mars wobbles as it spins on its axis. In turn, this should provide information on the internal structure of the planet--for example, whether it has a molten or metal core.

* ALL EYES ON MARS

Several venues will show live images from Mars. B2