Scientists revamp NEAR's mission Rocket failure sparks scramble to salvage asteroid flyby

December 23, 1998|By Frank D. Roylance | Frank D. Roylance,SUN STAFF

Racing to turn lemons into lemonade, scientists at the Johns Hopkins University Applied Physics Lab scrambled yesterday to build a new mission for their NEAR spacecraft after a rocket failure Sunday canceled plans to orbit the asteroid Eros on Jan. 10.

Instead, NEAR (for Near Earth Asteroid Rendezvous) was being reprogrammed to snap 500 photos of Eros as it flies by beginning at 1: 43 p.m. today.

It will then reconfigure for another attempt to orbit the asteroid the next time it comes around the solar system, in May 2000.

"They have assured me this is going to work," said APL spokesman Helen Worth.

"We love a challenge."

The NEAR spacecraft was designed and built at APL and launched in February 1996.

It was the first of NASA's "faster, better, cheaper" Discovery series.

In June 1997, it flew past a 41-mile-long asteroid called Mathilde and radioed back more than 500 pictures snapped from a distance of 753 miles -- the closest ever of an asteroid.

NEAR is 232 million miles from Earth.

APL scientists had planned to orbit Eros until February 2000.

With the vehicle circling as close as nine miles from the surface of the 25-mile-long rock, they hoped to gather a wealth of data about its structure and chemical composition.

The opportunity was lost when a critical rocket burn failed Sunday evening. An initial two-minute maneuver went as planned.

But just as the main engine began to fire, it shut down, and radio contact was lost.

NASA launched a search with the antennas of its Deep Space Network.

At 7: 30 p.m. Monday, its operators found a weak signal. It sounded like NEAR.

"By 8 p.m., they were able to tell us it definitely was NEAR," Worth said.

"I saw people smile who I hadn't seen smile for many hours. It was very jubilant. But they didn't take much time to celebrate," she added.

By 4 a.m. yesterday, controllers regained full contact.

They began to query the spacecraft for information on the rocket failure.

"Apparently there was no hardware damage," Worth said.

The cause of the rocket failure was unknown, but it was being laid to a software error.

When it comes time to fire it again for orbital insertion in May 2000, APL engineers expect it will work.

Eros will fly past the NEAR spacecraft today at a distance of about 2,500 miles.

That's more than three times farther away than the 1997 Mathilde flyby, so the quality of today's pictures of Eros will be poor compared with the Mathilde photos.

However, Eros will be moving much more slowly than Mathilde -- just 1 mile per second relative to NEAR, Worth said.

"What we will be able to determine is if it [Eros] has any moons. We will determine its size and shape. Scientists may also be able to estimate its mass.

"The advance look will help them plan for a safer encounter in May 2000 than they would have had next month.

"It gives us some advantages, though not enough to have wished this on ourselves," she said.

Pub Date: 12/23/98

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