Galileo Plasma Wave Investigation: Observations At Ganymede
NOTE: These images and Quicktime animation are made available in order to share with the public the excitement of new discoveries being made via the NASA/JPL Galileo spacecraft. Galileo scientists are in the process of calibrating and validating this data. The full digital data necessary for scientific analysis will be released within one year of receipt of this orbit's last data.
These images and animation are available only on the WWW; it is not available in hardcopy or other forms.
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On June 27, 1996, the Galileo spacecraft made the first flyby of Jupiter's largest moon, Ganymede. The Plasma Wave Experiment (PWS), using an electric dipole antenna, recorded the signature of a magnetosphere at Ganymede. This is the first example of a magnetosphere associated with a moon. The PWS data are represented here as both sounds and a rainbow-colored spectrogram. Approximately 45 minutes of PWS observations are transformed and compressed to 60 seconds. Time increases to the right and frequency (pitch) increases vertically. Color is used to indicate wave intensity, red corresponding to strong waves, blue corresponding to weak waves.
The audio track represents the PWS data and is synchronized with the display of the rainbow-colored spectrogram. The pitch of the sound is reduced by a factor of 9 from the measured frequency and follows the location of the signal on the rainbow-colored spectrogram. The entrance into the Ganymede magnetosphere is marked by a strong burst of noise about 6-10 seconds into the recording. As the spacecraft approaches Ganymede, an irregular tone can be heard rising in frequency, reaching a peak and then declining. The pitch of this tone is a measure of the density of charged particles near Ganymede. Both the plasma wave and magnetometer data show that a strong magnetic field exists around Ganymede.
Animation is courtesy of the Galileo Plasma Wave Science Team.
Launched in October 1989, Galileo entered orbit around Jupiter on December 7, 1995. The spacecraft's mission is to conduct detailed studies of the giant planet, its largest moons and the Jovian magnetic environment. The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC.
This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://www.jpl.nasa.gov/galileo. For further information, see the PWS home page at http://www-pw.physics.uiowa.edu/~wsk/galileo/ganymede/ganymede.html.