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Probe Records Halley's Heart in Riot of Color

March 14, 1986|LEE DYE | Times Science Writer

DARMSTADT, West Germany — A small European spacecraft survived just long enough to get the job done Thursday, dropping out of contact with Earth immediately after sending back the closest pictures ever of the nucleus of Halley's comet.

Traveling 50 times faster than a speeding bullet, Giotto carved its niche in history as it plunged through the heart of the comet, snapping photographs as it passed about 300 miles from Halley's icy core.

Brilliant Colors

Halley appeared in the photographs as though it were painted by a madman, sporting brilliant hues wrapped around a glistening center. The colors were not the real colors of the comet itself, but were instead "false colors" used by scientists to designate areas of common brightness.

But they created a surrealistic portrait of the famous comet, which has returned every 76 years to tantalize mortals who have stared at the heavens in awe.

The photographs appeared to have stripped the cloaks of dust and gas that Halley's has draped itself in for centuries.

The Real Nucleus

"We think this is the iceberg. We can assume this is the real nucleus we are seeing," Rainer Schwenn, a member of the camera team, said as the photographs flashed across scores of television sets at the European Space Operations Center here.

To Schwenn's practiced eye, the photos revealed "incredible detail."

He said he detected contours on the nucleus, and he said he could tell the difference between ice and dust on the surface.

While the camera clicked away, nine other experiments aboard Giotto examined the comet's magnetic field, captured and analyzed dust particles, and studied the gases and ionized particles that make up the plasma field that surrounds the nucleus.

Scientists will analyze that data for weeks before figuring out what it all means, but they were elated here Thursday by the fact that all of the experiments seemed to have worked perfectly.

It was not known for certain why Giotto's signal dropped dramatically just as the craft made its closest approach, but preliminary indications were that the craft had been so bombarded by dust that it started wobbling, and that would have kept Giotto's antennas from pointing toward Earth.

The craft was being bombarded at the "high rate" of 120 impacts per second during the last two minutes of the encounter.

Scientists, however, were elated over the images they saw, convinced they had at last seen the nucleus of Halley's comet.

"Halley had kept its true face hidden from us all, until tonight," a triumphant Reimer Lust, director general of the European Space Agency, told an ecstatic crowd here.

Enormous Energy

Halley and Giotto passed each other at more than 150,000 m.p.h.--a speed so great that a grain of dust hitting the spacecraft would have had the same kinetic energy as a crash with a small car.

The close encounter was the grand finale of the greatest week in the history of cometary science, during which the most famous wanderer in the solar system was visited by no less than five spacecraft that had traveled for up to 27 months to get there.

The space probes, sent by the Soviet Union and Japan in addition to the member nations of the European Space Agency, also signaled somewhat of a turning point in the history of the space age.

This was the first effort at interplanetary exploration by both Japan and Europe. The success of Giotto moved Europe forcefully into the competition for major scientific achievement in space, and the two Japanese spacecraft that successfully completed their modest goals proved that Japan's neophyte program is off and running.

"We have established our technology to go out into deep space," said Hiroki Matsuo of the Institute for Space and Astronomical Science in Tokyo. "We have passed the initiation into this interplanetary society, which has been monopolized by the two giants."

International Success

The success of the missions to Halley's marked a major milestone in international cooperation. One of the more difficult parts of the Giotto mission involved sending the spacecraft that close to the comet, yet managing to miss the hard, ice nucleus.

That was accomplished partly by determining the location of the comet in relation to the Soviet spacecraft on the basis of information supplied by the Soviets. That, plus information from the huge antennas of the U.S. space tracking network that told the Europeans exactly where the Soviet probes were, allowed the Europeans to target their spacecraft with utmost precision.

Named Pathfinder

The international effort was called Pathfinder.

Roald Sagdeyev, head of Moscow's Space Research Institute, noted that the navigational achievement permitted the Europeans to target their spacecraft on a comet that bears the name of "the greatest navigator of his century," Sir Edmond Halley.

Halley was the first to prove that some comets follow orbits around the sun, and he predicted correctly that the comet, later named after him, would return years after his own death.

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