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Halley's Armada

March 5, 2011

One of the most anticipated events in the history of astronomy was the 1986 return of Halley's Comet. The comet had last visited the inner solar system in 1910. But the tools for studying it then were primitive compared to those of the 1980s, so astronomers were looking forward to a scientific bonanza.

That bonanza included observations by an armada of spacecraft. Five probes flew past the comet, coming as close as a few hundred miles to Halley's icy nucleus.

The first to arrive was the Soviet Union's Vega 1, which flew past Halley 25 years ago tomorrow. The craft had already dropped a lander and a balloon at Venus. They probed the planet's dense, toxic atmosphere. Vega 1 stayed a safe distance from Halley, though, passing thousands of miles from the nucleus.

Over the next four days, another Soviet probe and two Japanese missions also made distant flybys.

The star of the show, however, was a European mission called Giotto. It passed about 350 miles from Halley on March 13th, and made the most extensive measurements of the comet and its surrounding cloud of gas and dust.

In fact, the dust gave Giotto quite a pounding. Even though the probe carried a shield to protect it from solid particles, dust grains rammed into it at thousands of miles per hour. They knocked out its camera and damaged other instruments. Even so, Giotto helped give scientists their best look at a comet in history.

Script by Damond Benningfield, Copyright 2011

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