This Week on Galileo
October 29 - November 4, 2001
Galileo Plays Back Data from the Io Flyby
The focus for Galileo this week is playback of the recorded data from the
October 15 flyby of Io. First up is the calibration for the
Photopolarimeter Radiometer instrument (PPR), which began our observing
sequence. PPR then turns its attention to several observations of Jupiter.
These measurements were made of a region of vortex-like storms near the
north pole of the giant planet, and of a long-lived white oval storm that
has been the subject of several observations during our stay in the Jupiter
system. Scientists also expect to see data from a thermal map of the dark
side of Io, taken while the spacecraft was still 11 hours away from its
The bulk of the week is taken up with the return of a two-hour-long
recording by the suite of instruments that measure the electromagnetic
fields and energetic particles that encircle the planet. These instruments
are the Energetic Particle Detector, the Heavy Ion Counter, the
Magnetometer, the Plasma Subsystem, and the Plasma Wave Subsystem. The
recording was made while the spacecraft was passing through the Ramp region
of the Io Torus. The torus is a doughnut-shaped area of increased radiation
and particle density that nearly coincides with the orbit of Io. The Ramp
is the transition between the background magnetosphere and the torus. It is
a region where the ion density and temperature of the environment increase
sharply, making it an intriguing target for exploration.
Also during this week the Magnetometer and Dust Detector instruments
continue to collect data about the immediate environment of the spacecraft
as the hardy explorer increases its distance from Jupiter from 100 to 125
Jupiter radii (7.1 million to 8.9 million kilometers, or 4.4 million to 5.5
million miles). These data are stored within the two instruments'
individual computer memories and periodically transmitted to Earth.
The Extreme Ultraviolet Spectrometer instrument is also collecting data,
studying the solar variation in the interplanetary hydrogen and helium
abundances. This instrument also stores its collected data in internal
buffer memory and periodically feeds this data into the main information
stream coming from the spacecraft.