Soviet Probe of Halley’s Comet Called a Success

The Soviet spacecraft Vega 2 flew to within 5,125 miles of the nucleus of Halley’s comet Sunday and sent back photographs and data that scientists said made the mission a success.

The spacecraft came almost 500 miles closer than a Vega 1 probe Thursday and relayed nearly 700 pictures to the space research institute here.

The missions helped to pave the way for a flight this week by the European Space Agency’s Giotto probe that is going to pass within 560 miles of the famous comet, which appears once every 76 years in the inner solar system.

Roald Z. Sagdeyev, director of the Soviet Space Institute, said Vega 2 photos indicate that Halley’s comet has a single nucleus rather than twin cores as scientists suspected after Vega 1 photos were received.

“It’s a rather irregular shape and we can’t see the details,” Sagdeyev told reporters a few hours after Vega 2’s closest contact with the comet at 10:20 a.m. Moscow time.

“There’s a strong indication that it’s a cocoon type of nucleus, a solid body surrounded by a soft dust blanket that is opaque and a couple of hundred meters thick,” he said.

John Simpson, professor of physics at the University of Chicago’s Enrico Fermi Institute, said a device he invented to collect dust samples from the comet’s tail aboard both Vega spacecrafts worked successfully.

“The instruments worked beautifully,” he told reporters. “There was no problem in coming closer (to the comet’s nucleus).”

Simpson said he believes that the instruments in the Giotto probe, contrary to predictions by some scientists, would survive the spacecraft’s brush with the comet.

“They are going to be OK--they are not going to have any trouble,” he predicted.

A Minor Hitch

There was a minor hitch in Sunday’s mission, however.

Something--perhaps a cosmic ray--struck the Vega 2 television camera, and its microprocessor failed. While scientists on the ground switched to a backup system, the camera exposure setting was a little bit off, scientists said.

As a result, the comet’s nucleus appeared white on the photographs, indicating over-exposure.

But Louis Friedman, executive director of the Planetary Society, based in Pasadena, Calif., said the photos are remarkably clear and have a wider perspective.

“The missions were a colossal success,” he said. “It’s hard to think of it being better.”

American scientists and observers said they especially appreciate the open access they have had to the Space Research Center, where the information was received.

Scientists from the Soviet Union were joined by colleagues from Austria, Bulgaria, Hungary, East and West Germany, France, Poland, Czechoslovakia and the United States in the operations room.

“A large volume of information has been received about the dynamic properties, structure and composition of that celestial body,” the official news agency Tass said of the Halley’s comet probes.

“The pictures received today (Sunday) show a greater sharpness and contrast range than the ones beamed back by Vega 1,” Lev Mukhin of the Soviet Space Institute was quoted by Tass as saying.

Scientists expect that the data may help to explain some of the mysteries surrounding the formation of the planetary systems.

Tass said the successful conclusion of the international project by scientists from East and West “demonstrates the real opportunities and broad vistas in the peaceful exploration of outer space through pooling the efforts of different states.”