‘86 Brush With Comet Will Take Space Probe Into Halley Dust Storm
The most daring of all the space missions to Halley’s Comet, set for launch today from French Guiana, will send a European craft so close to the comet that it is expected to be destroyed when it passes through a cometary dust storm and flies to within 300 miles of the nucleus.
The spacecraft Giotto, named in honor of Florentine painter Giotto di Bondone--who used the comet in the 14th Century to portray the Star of Bethlehem--was scheduled for launch at 4:13 a.m. Pacific time atop a European Ariane rocket. It will be a bold attempt to give the world a close look at the most famous comet in the heavens.
If all goes according to plan, more than nine months from now, on March 13, the unmanned spinning craft will plow through the cloud of dust that surrounds the comet, protected from the bombardment of particles by a shield made of the same composite material that is used to make bullet-proof vests.
The barrel-shaped spacecraft and the comet will be traveling in opposite directions, and they will pass each other at an incredible combined speed of about 45 miles per second. At that speed, scientists say, a grain of sand would penetrate a steel sheet half an inch thick.
In Harm’s Way
The environment that the spacecraft will pass through “is not only high risk, but highly unknown,†said John Brandt of the National Aeronautics and Space Administration. “No one should be surprised if that thing is wiped out.â€
Brandt, who is with NASA’s Goddard Space Flight Center in Greenbelt, Md., said the craft should be inside the comet’s tail for about an hour, and even if it survives the bombardment of dust particles it may be bumped so hard that its antenna no longer points toward Earth.
“It’s close, it’s hard, and it’s risky,†Brandt said. “If they pull it off, it would be magnificent.â€
Giotto is one of five missions to Halley, but none of the others will try to get that close. The two Vega probes launched by the Soviet Union last December are well on their way to Halley, stopping first at Venus and then whipping around the planet and spinning off toward the comet.
The first Vega will pass about 6,000 miles from the comet, and the results of that encounter will be used to determine how close the second Vega should approach the nucleus three days later.
Two Japanese probes, marking that country’s entry into the interplanetary space race, will try to stay at least 100,000 miles away from the comet’s center.
While the probes are being launched at widely differing times, all five will pass Halley within a one-week period, March 6 to 13.
Scientific Interest
All the crafts carry instruments designed to tell scientists more about the composition of the comet’s nucleus, believed to be a “dirty snowball†of frozen dust and gas, and the makeup of its tail, which will extend away from the sun hundreds of thousands of miles.
As it barrels through the tail, called a “coma,†Giotto’s instruments will determine the position of the comet and relay that information back to ground controllers who will try to keep the craft on course.
Scientists believe the nucleus of the comet is about three miles in diameter, and a color television camera on Giotto will be able to pick out surface details about the size of a small truck.
The craft also will carry 10 experiments from five European countries. Scientists from many other countries, including the United States, have collaborated on some of those experiments.
A Series of Visits
The object of all this attention, of course, is a comet that painter Giotto saw in 1301. A few years later, the comet was back again, but this time as the Star of Bethlehem in Giotto’s painting, “The Adoration of the Magi.â€
The comet has been back every 76 years, making a journey that has become steeped in folklore around the world.
