The Galileo mission consists of two spacecraft: an orbiter and an atmospheric probe.
Launched during the STS 34 flight of the Atlantis orbiter, the two spacecraft were kicked out
of Earth orbit by an inertial upper stage (IUS) rocket, sending them careening through the
inner solar system. The trajectory which the spacecraft followed was called a VEEGA
(Venus-Earth-Earth Gravity Assist), traveling first in toward the Sun for a gravity assist from
Venus before encountering the Earth two times (spaced two years apart). These encounters
with Venus and the Earth allowed Galileo to gain enough velocity to get it out to Jupiter.
During the flybys of Venus and the Earth, Galileo scientists took the opportunity to study
these two planets as well as the Moon, making some unprecedented observations as a result.
In addition, following each Earth flyby, Galileo made excursions as far out in the solar system
as the asteroid belt, enabling scientists to make the first close-up studies of two asteroids,
Gaspra and Ida. As is this were not sufficient, Galileo scientists were fortunate to be the only
ones with a direct view of the Comet Shoemaker-Levy 9 fragment impacts on Jupiter. All of
this was prior to the primary missions of sending an atmospheric probe into Jupiter's
atmosphere and studying Jupiter, its satellites, and its magnetosphere for two years with the
Interplanetary studies were also made sporadically by some of the other Galileo instruments,
including the dust detector, magnetometer, and various plasma and particles detectors, during
its six year journey to Jupiter.
The probe was released from the orbiter 147 days prior to its entry into the Jovian
atmosphere on 7 December 1995.