The Galileo Orbiter and Probe are to be launched with NASA’s new Space Shuttle and Inertial Upper Stage. To carry the maximum possible payload to Jupiter, a close flyby of Mars is planned en route. The gravitational field of Mars will give a boost to Galileo, just as that of Jupiter was used by Voyager to swing on to Saturn.
The exact launch date and trajectory for Galileo have not yet been specified, but if all goes well, the Orbiter spacecraft will approach Jupiter from the dawn side of the planet sometime in the mid-1980s. It will not be moving as fast as Voyager, since it must be placed into orbit around Jupiter rather than flashing past on its way to the outer solar system. On its initial trajectory, Galileo will probably come within 5 R_J of Jupiter, slightly closer than Voyager 1. At this time it will fire its rocket engines (supplied by the Federal Republic of Germany in a cooperative program with NASA) to shed excess speed and let itself be captured by Jupiter’s gravity. The first pass will also be the time for a close flyby of Io.
[Illustration: The most critical period of the Galileo flight will be the Probe entry at Jupiter. The Probe must strike the atmosphere at precisely the correct angle and speed to be slowed down without being destroyed. At a pressure level of about 0.1 bar the rapid deceleration period ends and the heat shield is released. A parachute is deployed to slow the descent further, and the Probe then has a period of nearly an hour to study the atmosphere and clouds of Jupiter. The Probe mission ends when its batteries run down or when it is crushed by the pressure of the Jovian atmosphere near the 20-bar level, whichever comes first. [SL78-545(3)]]
GALILEO PROBE SCIENCE INVESTIGATIONS Probe Scientist: L. Collin, NASA Ames Investigation Principal Investigator Primary Objectives
Atmospheric structure A. Seiff, NASA Ames Measure temperature, density, pressure, and molecular weight to determine the structure of Jupiter’s atmosphere. Neutral mass H. B. Neimann, NASA Measure the spectrometer Goddard composition of the gases in Jupiter’s atmosphere and the variations at different levels in the atmosphere. Helium abundance U. von Zahn, Bonn U. Measure with high interferometer (Germany) accuracy the ratio of hydrogen to helium in Jupiter’s atmosphere. Nephelometer B. Ragent, NASA Ames Determine the sizes of cloud particles and the location of cloud layers in Jupiter’s atmosphere. Net flux radiometer R. W. Boese, NASA Ames Measure energy being radiated from Jupiter and the Sun, at different levels in Jupiter’s atmosphere. Lightning and radio L. J. Lanzerotti, Measure lightning emission Bell Labs flashes in Jupiter’s atmosphere, from the light and radio transmissions from those flashes. Energetic particles H. M. Fischer, U. Measure energetic Kiel (Germany) electrons and protons in the inner regions of the Jovian radiation belts and determine their spatial distributions.