dipper@utastro.UUCP (Debbie Byrd) (01/08/86)
A shuttle mission will observe Comet Halley. More on studying the comet from space -- after this. January 8 The Spartan Halley Mission Comet Halley is being studied from Earth -- and from space. Later this month the shuttle Challenger will carry instruments into Earth orbit to observe Comet Halley. The mission is scheduled for late January -- just before the comet comes closest to the sun on February 9th. The shuttle mission will be studying Comet Halley when its small icy nucleus or core is becoming most active. The comet heats up as it nears the sun. As the temperature rises, the ices in the comet's nucleus sublime -- change directly from solids into gases. The frozen nucleus is made mostly of water -- hydrogen and oxygen molecules. Other molecules of gas are trapped within the lattice framework of the water ice. As the ice evaporates, it releases the other gases. The composition of the gases can change as they boil off the comet. For instance, the water ice breaks down into hydrogen and hydroxyl molecules. Aboard the shuttle Challenger are special instruments called spectrometers. The spectrometers will measure the comet in the ultraviolet wavelengths of light. The Earth's atmosphere blocks out most ultraviolet light from reaching the surface of our planet -- and those are the wavelengths that reveal the presence of water molecules -- especially the large cloud of hydrogen surrounding the comet's nucleus. The spectrometers for the comet mission are similar to ones that were used on spacecraft sent to study the planet Mars. The astronauts will use the shuttle's robot arm to place the small package containing the instruments into its own orbit. Forty-eight hours later they'll retrieve the equipment -- with its data on Comet Halley. Script by Diana Hadley. (c) Copyright 1985, 1986 McDonald Observatory, University of Texas at Austin