Thrills - and no spills - in NASA's asteroid landing

It was a moment Giuseppe Piazzi might have savored.

On Jan. 1, 1801, in the days when astronomers actually peered through eyepieces in the back ends of telescopes to learn about their cosmic neighborhood, the Italian monk spotted an object in the night sky that failed to show up in a star catalog he was revising. He had discovered the first asteroid, later named Ceres.

Two hundred years later, planetary scientists hugged and high-fived as they added another chapter to the history of solar-system exploration: landing on an asteroid.

While the landing Monday came long after the cold-war space race, it marked a national as well as a scientific breakthrough: the first time the United States has been first to land a craft on any object in the solar system. (Russian missions made the initial touchdowns on the moon, Mars, and Venus.)

Today, NASA tracking stations are scheduled to pull the plug on communications links to the craft, which has been beaming "I'm OK" signals since it touched down at 3:02 p.m. Eastern time Monday.

The landing caps a year-long study of the asteroid Eros, and researchers involved in the mission are thrilled with the results. "The payoff has been tremendous," says Joseph Veverka, a Cornell University astronomer who led one of the science teams for the Near Earth Asteroid Rendezvous (NEAR).

Indeed, the $223 million mission epitomizes NASA's current style, which milks the most out of its lean funding. The so-called NEAR Shoemaker craft came in $8 million under budget, leaving more money for the mission's research.

And in a way, the scientists have gotten three missions out of one.

For the seven months it orbited Eros, the spacecraft sent back a global view of the asteroid "that answered all the basic questions we were smart enough to ask," Dr. Veverka says. Then mission managers tweaked the craft's orbit to bring it closer to the surface last fall. Images showed features - rocks with fine dust rings around them, and evidence of silt that slumped down the side of craters and ponded at the bottom - that left researchers scratching their chins. Monday's touchdown represents the third mission, and even here, closer images as the craft neared the surface have revealed puzzling features.

Apart from the science, Monday's landing has written a new chapter in space-navigation textbooks - setting a craft down on an oblong space rock that is slowly tumbling end over end as it orbits the sun. "I'm a believer in Murphy's law, and there were a couple of hundred things that could have gone wrong," says mission director Robert Farquhar. "But it went perfectly."

The impressive landing was controlled not from Houston but from a cramped room at the Johns Hopkins University's Applied Physics Laboratory here.

"That's some straight shootin'," whispered one watcher in in a nearby auditorium, where an audience was made up largely of friends and relatives of those involved in the mission. A computer was tracing the craft's glide path to the surface and comparing it with what planners hoped would happen. The match was virtually perfect.

But "straight shootin' " hasn't always been this mission's mode..

NEAR was to have started orbiting Eros in 1999, but an engine misfired that December, sending the craft hurtling past the asteroid and back into deep space. "I left the control room in a state of shock," recalls scientist Andrew Cheng. "Part of me was concerned we'd never hear from the spacecraft again. I went to bed that night looking like a zombie."

That event makes the mission's success all the more fantastic.

The experience landing on oddly shaped low-gravity objects is expected to benefit missions planned by the European Space Agency and Japan to put landers on a comet and an asteroid. "NEAR has set a foundation for future asteroid missions," says Richard Binzel, an asteroid expert at the Massachusetts Institute of Technology. "The next steps ... would be to visit protoplanets like Ceres, Vesta, and Juno. Today, we're putting the first robotic footprint on the surface of one of these tiny worlds. Someday in the far future, we may follow with the first human footprints."

(c) Copyright 2001. The Christian Science Publishing Society