Spacecraft keeps date with Eros

Valentine orbit melds science, sentiment

February 15, 2000|By Frank D. Roylance | Frank D. Roylance,SUN STAFF

In a Valentine's Day marriage of science and sentiment, a Maryland-built spacecraft slipped into orbit yesterday around an asteroid named for the Greek god of love.

After a 57-second thruster firing at 10: 33 a.m., the Near Earth Asteroid Rendezvous spacecraft slowed its speed to that of a lover's stroll and slipped into a 280-mile-high orbit around the asteroid Eros, where it immediately began taking pictures.

It is the first man-made object ever to orbit an asteroid, and its arrival at Eros on Valentine's Day was a calculated melding of science and public relations.

To scientists eager to learn more about asteroids as pristine remnants of the early solar system, the day seemed more like Christmas Eve.

"All the presents are piling up under the tree, and soon we'll find out what's in all the boxes," a smiling NEAR project scientist Andrew Cheng said at the Johns Hopkins University Applied Physics Lab (APL) in Laurel, which is managing and controlling the mission. Yesterday's rendezvous took place about 162 million miles from Earth, near the orbit of Mars.

Eros is 20 miles long and 8 miles wide -- almost the size of Howard County. The first close-up photos returned by NEAR at 12: 40 p.m. yesterday showed it to be heavily cratered, as expected.

But scientists were surprised to see evidence of layering on the sides of a 3.4-mile-wide crater. There were also signs of slumping in the soil on the crater wall and the vertical tracks of boulders that had rolled from the crater's rim.

Some scientists had doubted whether Eros' weak gravity could produce such effects. A 200-pound man on the surface of Eros would weigh barely 2 ounces. And if he could run a 100-yard dash in 9 seconds (22 mph), he could launch himself into space.

`Exciting geology'

"There's a lot of exciting geology, and this is only the beginning," said Joseph Veverka of Cornell University, who heads NEAR's imaging team.

Scientists at APL were also busy yesterday analyzing the first spectroscopic data on Eros' mineral composition. Veverka said the information "looks absolutely fantastic."

It was too soon for any preliminary results. But NEAR's reports from Eros in the coming year are expected to yield clues as to how the swirling cloud of gas and dust that formed the solar system an estimated 4.5 billion years ago sorted itself out to form the sun, the rocky inner planets, the giant outer gas planets and the icy objects beyond Pluto.

Most asteroids -- tens of thousands of them -- circle the sun in the doughnut-shaped "main asteroid belt" between the orbits of Mars and Jupiter. There are enough of them to have formed a small planet. But Jupiter's huge gravitational influence has kept them stirred up like stew in a pot.

Pieces of those asteroids are thought to have fallen to Earth for billions of years as meteorites. But scientists have never been certain which of the kinds of meteorites they have found correspond to which classes of asteroids they have seen through their telescopes.

The $216 million NEAR mission "will enable us to link our meteorite knowledge to our asteroid knowledge," said Noam Izenberg, a member of APL's NEAR team.

Launched in 1996

NEAR, launched in 1996, will remain in orbit around Eros for nearly a year before its fuel and its budget are exhausted. It is controlled from APL's Laurel campus, where yesterday's success was greeted by cheers and applause.

The day was especially sweet in light of NEAR's brush with failure in December 1998, when a critical engine firing was inadvertently aborted by an on-board computer. Controllers grabbed some photos as the asteroid flew by, then began a yearlong pursuit that ended yesterday.

Daniel S. Goldin, administrator of the National Aeronautics and Space Administration, congratulated the NEAR team yesterday for its skill and pluck. "You don't often get a second chance at love," he quipped.

Sen. Barbara A. Mikulski, a Maryland Democrat, called it "a great morning." She noted that NEAR's analyses of Eros' structure and composition could help in the design of an effective means to deflect or destroy any asteroid found to be headed toward a collision with Earth.

"This is absolutely crucial," she said.

Mission manager Robert F. Farquhar noted that NEAR is the sixth craft in 43 years of space exploration to make the initial orbit of a celestial body. It follows Sputnik 1 (the first to orbit Earth, in 1957); Luna 10 (the moon, 1966); Mariner 9 (Mars, 1971); Venera 9 (Venus, 1978); and Galileo (Jupiter, 1995).

It is also the first to orbit such a small body, which is no small feat. Eros' mass, and consequently its gravitational pull, are barely enough to hold NEAR in orbit. To achieve orbit, controllers at APL had to slow the spacecraft's speed relative to the asteroid to 1 meter per second, about 2.2 mph.

The elongated asteroid's spin makes NEAR's orbit unstable. APL controllers will have to make repeated orbital adjustments to avoid a crash.

The craft is circling Eros once every 27.6 days, at an altitude ranging from 203 miles to 280 miles. In coming months, controllers will gradually lower the orbit to within 31 miles of the asteroid. NEAR will remain there for at least four months while conducting its primary science mission.

Planners hope to lower the spacecraft to as little as nine miles above the asteroid before the mission ends, and they might attempt a crash landing.

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