dipper@utastro.UUCP (Debbie Byrd) (12/04/85)
This is the anniversary of a spacecraft placed in orbit around the planet Venus. More -- after this. December 4 Pioneer Venus On February 9, Halley's Comet reaches perihelion, its closest point to the sun for this 76-year orbit. Halley is about 55 million miles from the sun on February 9. Meanwhile, Earth is about 150 million miles from the comet, on the opposite side of the sun. That's why, at this perihelion, Comet Halley is impossible to see from our world. While closest to the sun, Halley should be about at its best. Its flowing tail should be longest -- its surrounding coma should be greatest in extent. But, because the comet happens to be behind the sun from us when it's at perihelion, we won't be able to see it then. After February 9, Halley will remain invisible from Earth until at least late February. And yet, at this perihelion, an emissary from Earth will be in the vicinity of Halley. The planet Venus is near Halley then, only about 30 million miles away. And there is a NASA spacecraft orbiting Venus -- placed in orbit on today's date in the year l978. In February, Pioneer Venus will turn its gaze away from the planet -- toward the glittering spectacle of Comet Halley coming home to its mother star. Pioneer Venus gave us the interesting radar map showing highland and lowlands on Venus. It gave good information on the impenetrable venusian clouds. In February, the spacecraft's ultraviolet spectrometer will be used to look at Comet Halley. The Pioneer data will work with information from the many other observations of Halley -- both from Earth and from space -- to provide a detailed scientific portrait of the comet -- and make Halley the best-known comet in history. Script by Deborah Byrd. (c) Copyright 1984, 1985 McDonald Observatory, University of Texas at Austin