QUESTION:
What will Cassini learn that we do not already know from Voyager and Hubble
Space Telescope data?

ANSWER from FAQ on June 3, 1999:
The Voyager flybys represented an initial reconnaissance of Saturn. The
Voyagers provided measurements of selected targets over the few days
the spacecraft traversed the Saturnian system. Cassini represents a
follow-on to the Voyagers. Cassini will perform in situ (directly
within the environment) studies of Titan's atmosphere and surface. The
Cassini orbiter instruments are capable of at least a tenfold increase
in resolution and coverage over the earlier data. They will also have a
greater capability to study time variations in the Saturn system over a
four-year period instead of snapshots during relatively brief flybys.
The Cassini mission objectives are split into five main areas: Saturn's
atmosphere and interior, the rings, the magnetosphere, Titan, and the
icy satellites. The orbiter will conduct long-term, detailed, close-up
studies of the rings, satellites and planet, and perform in situ
measurements of Saturn's magnetosphere. None of Cassini's scientific
objectives can be completed by the Hubble Space Telescope due to
Hubble's distance from Saturn and the amount of time HST can spend on
focusing on a given target.