dipper@utastro.UUCP (Debbie Byrd) (03/18/85)
Five space missions are planned to intercept Comet Halley. More on when and where they'll meet the comet -- after this. March 18 Five Missions to Halley By this time next year, five space probes from Earth hopefully will have visited Comet Halley. The two Soviet spacecraft were launched last December -- they're taking the scenic route to Halley via the planet Venus. Japan launched its first Halley spacecraft in January -- with a second launch scheduled for August. And the European Space Agency's probe -- planned to come nearest Halley -- will be launched in July. The spacecraft will pass at different distances from the comet. But all five mission plans call for rendezvous with Halley during the first two weeks of March in 1986. As with all interplanetary space missions, sending a spacecraft to Halley is not a matter of simply going from point A to point B. When you launch a spacecraft from Earth -- you send it not to where the other object is now -- but where it's going to be when the spacecraft gets there. We're on a planet orbiting around the sun. Comet Halley's also moving around the sun -- in the opposite direction from Earth. Also, Halley's orbital plane is tilted to that of the Earth. For almost all of its 76-year orbit, Halley travels south of the plane of Earth's orbit. Only when it's near the sun -- for about three months -- does Halley travel north of Earth's orbital plane. In early March of 1986 Comet Halley will be crossing the plane of our planet's orbit. Then it'll be in an advantageous position for as many as five planned spacecraft from the planet Earth to pass near it. Script by Diana Hadley. (c) Copyright 1984, 1985 McDonald Observatory, University of Texas at Austin