When it last visited a simpler Earth 75 years ago, Halley’s Comet was viewed as a harbinger of evil, a celestial warning of impending doom. Monarchies were supposed to fall, man was to take up arms against his fellow man.
But while it is still more than 200 million miles away, Halley is returning to Earth this year with a different message. By the time it loops around the sun and begins the long journey back to deep freeze on the fringes of the solar system, the comet will have united people on Earth in an extraordinary way.
Five probes from three parts of the world will pass near the comet, and the information they collect will be shared by all scientists, regardless of national origins. The joint effort, involving state-of-the-art technology costing billions of dollars, is being coordinated by an elite group of scientists from such divergent cultures as the Soviet Union and the United States.
The probes are being sponsored by space agencies from Japan, the Soviet Union and a consortium of European nations. American scientists will not have a spacecraft of their own traveling to the comet but have joined the efforts of the foreign missions.
The comet scientists have met five times to ensure that all will share in the prodigious quantities of information that will flow to Earth, and they plan to meet again after the comet has left, hoping that the enigmatic space wanderer has left behind a heritage that will outlive their efforts.
The international committee that is coordinating the project has selected a name for the program that reflects that sentiment. It is called Pathfinder.
“There has simply never been anything like it,” said Burton I. Edelson, head of the space science and applications office of the National Aeronautics and Space Administration.
“We’ve had bilateral agreements between nations, but at no other time have we had a multinational effort involving all four space agencies,” said Ray Newburn of Pasadena’s Jet Propulsion Laboratory, who is director of the International Halley Watch.
The Halley project is probably the most ambitious multinational scientific program since the International Geophysical Year of 1957-58, when scientists from 67 nations took part in a vast study of the physical environment. However, the International Geophysical Year was put together primarily through non-government channels, in contrast to the Halley mission, which involves giant governmental bureaucracies in many countries.
More than 900 professional astronomers from 47 countries will take part in the Halley effort, and hundreds of amateurs will join in.
“Virtually every major telescope in the world will be used for this study,” Newburn said.
Thousands of scientists and technicians from around the world will devour the data from a range of sophisticated instruments, but what sets the program apart is the spirit of cooperation between the many nations and agencies involved.
“The attitude has been ‘How can we help each other?’ ” said Newburn, a member of the coordinating committee, called the Inter-Agency Consultative Group.
“We will be getting much better returns than if each nation had done its job separately,” said Roger Bonnet, the European Space Agency science director.
The mission will be coordinated so closely that information from the first probes to reach Halley will be used to retarget the one that arrives last and is targeted to pass closest to the comet.
First on the scene will be one of two Soviet spacecrafts, called Vega 1, which was launched last December. The Soviet probes carry instruments from scientists representing 10 nations, including the United States.
Most Daring Effort
The information supplied by Vega 1 will be especially important to the European Space Agency. The 11 nations that comprise that agency have fielded the most daring effort of all. Their spacecraft, called Giotto, is scheduled to fly within about 300 miles of Halley’s nucleus, and many scientists fear that the dusty cloud that surrounds the nucleus will destroy the craft.
Vega 1 will pass within 6,000 miles of Halley on March 6--eight days before Giotto is to plunge into the highly charged cloud that surrounds the nucleus--and information from the Soviets could warn the Europeans in time to retarget Giotto for a safer distance if Halley is too intimidating.
“The first pictures (from Vega) will be transmitted a few days before the closest approach,” said Roald Sagdeev, director of the Institute for Space Science in Moscow who is also a committee member. “They will be available worldwide.”
Japan’s maiden encounter with space, consisting of two probes intended to pass Halley at a safe distance of well over 100,000 miles, will provide a similar service.
From that distance, “we will supply data for more precise study by other spacecraft,” said Kunio Hirao of Japan’s Institute for Space and Aeronautical Science.
NASA decided against sending a spacecraft to Halley because of cost considerations, but that does not mean U.S. scientists will be left out.
American scientists “have exhibited a lot of individual enterprise and Yankee ingenuity in getting involved in Halley projects,” said Geoffrey Briggs, head of NASA’s delegation to the committee. Many Americans have experiments aboard foreign spacecraft en route to Halley, and many U.S. facilities will be actively engaged in studying the comet.
While the probes are passing Halley, NASA will use the space shuttle to observe the comet with a high-resolution telescope system, called Astro-1. And some American scientists have already made major contributions through the successful encounter earlier this month between a U.S. spacecraft and another comet, Giacobini-Zinner.
The European Space Operations Center in West Germany will act as sort of a clearinghouse for data from the five probes, and each country will also supply photographs and data directly to other agencies.
“I expect you’ll also see people camping out on the doorsteps of other agencies,” Newburn said.
Comradeship on Committee
The effort to coordinate the study of Halley has led to a strong sense of comradeship among committee members, a feeling demonstrated during the panel’s meeting in Washington earlier this month.
“We’ve actually become very good friends,” Newburn said.
Sagdeev, a leading Soviet scientist, was asked about the chances of survival for Vega 1 and Vega 2 during the meeting.
“In the worst case, we have prepared to have a kind of kamikaze mission,” he said, referring to the Japanese suicide squadrons of World War II. He suddenly reached over and with a boisterous laugh put his arm around the man sitting to his left, the delegate from Japan.
“I apologize,” he said, bringing the house down.
The Open Question
Whether their efforts will lead to lasting cooperation among the nations involved is open to question.
“Generally, all of us have found this such a satisfactory way to do business that we would like to see it continue,” Newburn said. “People you work with are people you are less likely to fight.”
That is consistent with a view expressed during the meeting by Sagdeev.
“May I express the modest wish for all humankind to see Halley’s Comet when it returns,” he said.
After a brief pause, he added: “In 2061.”