From the Project Manager

Project Galileo continues to perform superbly. Yes, Project Galileo--not just our magnificent spacecraft, but equally important, the hundreds of people on the ground that make it work. The people of the Project Team, including our German propulsion colleagues here and there, Galileo scientists worldwide, the people in the JPL Multimission Ground Systems operations, and those in the Deep Space Network at Pasadena and the tracking sites in California, Spain, and Australia, including the folks at Australia's Parkes 64-m antenna. The ensemble of all the things that must be done on a continuing basis to "operate" Galileo is truly mind-boggling. The lead time ranges from years to at times only minutes. It is an enormous plan of steadily increasing detail as a set of observations or a downlink nears. And, quite often, contingencies require the most insightful troubleshooting and recovery actions. It is a global team of the first magnitude.

Since the last Messenger just 2 months ago, the Ganymede-7 and Ganymede-8 encounters have been successfully performed--Galileo is now 7 for 7 orbital tour satellite encounters, less than 1 year since starting with Ganymede-1 in June 1996. Once again these recent encounters were punctuated with skillful real-time anomaly recoveries. Less than a day before Ganymede-7 closest approach, celestial reference was lost when the bright body protection "blocked" one of the two stars being used. The problem was diagnosed, and a different star was substituted by real-time commanding just hours before closest approach. Two days before Ganymede-8, it was discovered that the inboard Magnetometer sensor was opposite the planned orientation (flip), and the corresponding transformation matrix had to be real-time commanded several times throughout the encounter.

This past week, the Project Science Group (PSG) held its quarterly meeting at JPL. Excellent progress was made in planning the science observations for the Galileo Europa Mission (GEM). One day of these PSG meetings is now devoted to reports by the investigators of their latest science results. These reports show the tremendous breadth, quality, and quantity of science Galileo is providing. Publicly, the pictures from Galileo's Solid-State Imaging (SSI) camera always steal the show, just as in this issue of The Messenger, highlighting the "mind-boggling" Europan icebergs. There are ten other instruments on the Galileo Orbiter and two radio science investigations, all of which are providing excellent scientific results. We continue to struggle to find better ways to communicate the excitement and importance of the non-imaging data to the general public. Just a few examples: the Radio Science Celestial Mechanics Investigation "senses" the internal structure of the satellites and has discovered that Io, Europa, and Ganymede all have dense cores while Callisto is uniform throughout. The fields and particles instruments have discovered that Ganymede is magnetized, possibly Io as well, Callisto definitely not, and Europa yet to be determined. And they continue to map the composition and dynamics of Jupiter's lethal magnetosphere--the largest volume in our solar system at one-hundred times the volume of the Sun. This summer between the Callisto-9 and Callisto-10 encounters, Galileo carries these instruments 10 million kilometers deep into the magnetotail opposite the Sun to achieve one of Galileo's most important science objectives.

The Near-Infrared Mapping Spectrometer (NIMS) is providing excellent data to study the surface chemistry of the satellites, including volcanic hotspots on Io, and is, in effect, doing water sounding over the Jupiter globe--to mention just some of its contributions. The water sounding is providing important information about one of the major puzzles from the Probe observations--the apparent underabundance of water. NIMS data are showing that local water abundance below the clouds varies widely across the planet, suggesting that, indeed, Jupiter weather dried out the region where the Probe descended.

By the way, the original, official Project Plan for Galileo published in 1978 had NO encounters of Europa or Io, and the encounters of Ganymede and Callisto were all at or above a 1000-km altitude. Galileo has already encountered all four Galilean satellites typically at lower altitudes with a low of 261 km at Ganymede-2.

Galileo is indeed superbly fulfilling its objectives at Jupiter.

--Bill O'Neil
Project Manager

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