dipper@utastro.UUCP (Debbie Byrd) (09/20/84)
A NASA spacecraft in orbit around Venus will be used to study Halley's Comet. More -- right after this. September 20 Halley's Comet and Pioneer Venus Last week we talked about the NASA spacecraft called ICE, which was studying the sun -- but which is now on a mission to Comet Giacobini-Zinner. The idea for that mission came after NASA didn't get funding to send a craft to Comet Halley -- although three spacecraft from other nations will go. But NASA has another good plan to get spacecraft observations of the world's most famous comet -- with another craft on an entirely separate mission. This time, the spacecraft is in orbit around Venus -- it's the Pioneer Venus Orbiter, which gave us the spectacular topographical maps of Venus -- made by bouncing radar signals from the surface of that cloud-covered world. Pioneer Venus will be in a unique position to study Comet Halley when it's nearest the sun, and most active. Earth will be on the opposite side of the sun at that time -- so observations from Earth will be difficult. But Venus will be fairly nearby -- and Pioneer Venus, which has now been in orbit for five years, will be turned to take a look at the comet. An instrument on Pioneer Venus called an Ultraviolet Spectrometer will be used to study Comet Halley. It will help us learn what gases are in the comet -- how fast its water is evaporating -- and the ratio of gas to dust. That'll all take place in early 1986, around the time of Comet Halley's perihelion, or closest point to the sun. Script by Deborah Byrd. (c) Copyright 1983, 1984 McDonald Observatory, University of Texas at Austin