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NASA Plans to Land Research Craft on Eros Asteroid Monday Closing in on the Eros Asteroid to Conduct Research

By Curt Suplee
THE WASHINGTON POST -- An airless lump of rock that looks like a mutant spud is about to become one of the scientific celebrities of the solar system. Monday, NASA’s NEAR spacecraft is scheduled to reach the asteroid, called 433 Eros, ending a dogged, four-year pursuit with a rendezvous 160 million miles from Earth.

If all goes according to plan, the 1,775-pound spacecraft -- about the size of a highway toll booth topped by four solar panels -- will ease up to Eros at 33 feet per second, fire its braking jets, and snuggle into orbit around the asteroid.

“That would be a major first,” said Robert Farquhar, mission director for NEAR, short for Near Earth Asteroid Rendezvous. “No one has ever orbited a small body in space.”

Spacecraft have encountered several other asteroids at a distance since 1991, and the NEAR probe itself got within 750 miles of a dark, porous, carbon-rich blob called 253 Mathilde in June 1997. But the Eros visit is intended to be up close and extremely personal.

Over the next 12 months, NEAR’s instruments will measure Eros’s mass, shape, surface characteristics, gravity field, elemental content, mineral composition and magnetic field, among other things. The probe is scheduled to descend gradually until it hovers 1,600 feet above Eros’s surface, and might eventually attempt to land on the itinerant mini-world, which is about twice the size of Manhattan.

Originally, NEAR was supposed to cohabit with Eros in January 1999. But during the approach, something went wrong with the thrusters. The spacecraft accelerated abruptly, started tumbling, locked itself down into “safe” mode and refused to take calls for 27 hours. When mission managers regained control, the NEAR probe snatched only a couple hundred drive-by images of Eros, getting no closer than 2,378 miles.

The rock is scientifically fascinating for many reasons. For one thing, it is a representative of about 800 known near-Earth asteroids (NEAs) -- those whose orbits take them within about 30 million miles of Earth. Only a fraction of those have diameters exceeding 1 kilometer, or six-tenths of a mile.

Eros, which orbits the sun every 643 Earth days, was the first NEA observed, in 1898. It’s 21 miles long, 8 miles wide and 8 miles deep.