Torrence Johnson Biography

Engineers integrate the atmospheric probe with the Galileo orbiter before launch preparations are completed at Kennedy Space Center.

The Galileo spacecraft arrives at Kennedy Space Center for final testing, mating with its probe and launch preparations.

Galileo flies past Venus for a gravity assist on its journey to Jupiter and obtains additional planetary observations.

Galileo instruments observe Venus's clouds and atmospheric properties during the spacecraft's gravity-assist encounter.

During the first Earth flyby, Galileo obtains images of Earth and the Moon for calibration and planetary studies.

Galileo flies past Earth for a gravity assist that increases its heliocentric speed on the journey to Jupiter.

Galileo's high-gain antenna fails to deploy fully, forcing the mission to rely on its lower-bandwidth low-gain antenna.

Galileo observations establish Gaspra's strongly irregular shape and provide the first close spacecraft measurements of an asteroid.

Galileo becomes the first spacecraft to make a close encounter with an asteroid when it passes Gaspra.

Galileo images Gaspra as an irregular, heavily cratered asteroid with a surface layer of loose material.

During its second Earth encounter, Galileo obtains views of the Moon useful for studies of lunar surface composition.

Galileo makes a second Earth gravity assist, completing the planetary slingshot sequence that sends it toward Jupiter.

Galileo flies past asteroid Ida, becoming the second spacecraft encounter with an asteroid.

Galileo images Ida's heavily cratered surface and extensive regolith during the close asteroid encounter.

Scientists examining Galileo images discover Dactyl orbiting Ida, the first moon ever found around an asteroid.

Galileo observations establish that asteroid Ida possesses a natural satellite, showing that asteroid moons can exist.

Galileo observes Shoemaker-Levy 9 impacts on Jupiter's far side from a unique spacecraft viewpoint.

Galileo becomes the first spacecraft to enter orbit around Jupiter.

Galileo data strengthens evidence for a subsurface ocean at Europa.

Galileo makes the first of its close Ganymede encounters during its Jupiter orbital mission.

Galileo makes another close Ganymede encounter, passing much nearer the surface than during its first targeted flyby.

Galileo makes its first close pass of Callisto, mapping the moon's ancient cratered surface.

Galileo makes its first targeted close flyby of Europa and images its fractured icy terrain.

Galileo images reveal disrupted blocks of Europa's icy crust that appear to have rotated and shifted relative to surrounding terrain.

The scarcity of large impact craters in Galileo images indicates that Europa's visible surface is geologically young.

Galileo measures evidence of Ganymede's magnetic field.

Galileo imaging documents major surface changes on Io caused by continuing volcanic eruptions.

Galileo passes within about 586 kilometres of Europa and images additional regions of its fractured icy surface.

Galileo conducts another Ganymede encounter, extending surface, plasma and magnetic observations.

Galileo returns to Ganymede for another targeted encounter during its primary Jupiter tour.

Galileo results indicate Europa has a differentiated interior with a metallic core and rocky mantle.

Galileo flies close to Callisto, adding detailed imaging and geophysical measurements of the heavily cratered moon.

Galileo performs another targeted Callisto encounter late in its primary mission.

Galileo returns to Europa for another close encounter near the end of the primary mission.

NASA approves an extended Galileo mission emphasizing repeated close encounters with Europa.

Galileo makes a close Europa flyby as the extended Galileo Europa Mission begins.

Galileo makes another targeted pass of Europa during the extended mission.

Galileo conducts a further Europa encounter to examine the icy surface and surrounding environment.

Galileo returns to Europa during a sequence of repeated extended-mission encounters.

Galileo passes Europa again, continuing the extended survey of its geology and space environment.

Galileo performs another Europa flyby during the Europa Mission extension.

Galileo gravity and magnetic observations improve models of Callisto's internal structure and possible subsurface conductive material.

Galileo completes another close pass of Europa before shifting the extended mission toward Callisto and Io encounters.

Galileo uses a Callisto encounter as part of a campaign to reshape its orbit for later close passes of Io.

A second 1999 Callisto flyby further lowers Galileo's closest approach to Jupiter in preparation for Io observations.

Galileo performs another Callisto gravity-assist encounter during the perijove reduction campaign.

Galileo completes the final Callisto encounter in the sequence used to prepare for close Io flybys.

Galileo passes roughly 611 kilometres above Io, beginning exceptionally close extended-mission studies of the volcanic moon.

Galileo passes close to Io to investigate active volcanism and the moon's interaction with Jupiter.

Galileo begins the Millennium Mission with another close flyby of Europa.

Galileo flies about 198 kilometres above Io, obtaining close measurements of its active volcanic environment.

Galileo makes another close Ganymede pass, extending measurements of its surface and magnetic environment.

Galileo performs a distant Ganymede encounter while coordinating broader Jupiter-system observations with Cassini.

Galileo observations support the conclusion that Jupiter's faint rings are continually replenished by impact-generated dust from small inner moons.

Galileo passes only about 138 kilometres above Callisto during a close encounter.

A close Galileo flyby examines Io's rapidly changing volcanic surface at high resolution.

Galileo passes about 184 kilometres above Io during a late-mission encounter focused on volcanic and plasma activity.

Galileo results support the presence of extremely thin surface-bound exospheres around Europa, Ganymede and Callisto.

Galileo observations establish that Io's volcanic activity is vastly more extensive and energetic than volcanism on modern Earth.

Galileo completes its final Io flyby at an altitude of roughly 102 kilometres.

Galileo makes its final satellite encounter, passing close to the small inner moon Amalthea.

Over its mission, Galileo returns about thirty gigabytes of scientific data and roughly fourteen thousand images from the Jupiter system.

Galileo's years in orbit provide the first long-duration investigation of the global structure and variability of a giant planet's magnetosphere.

Routine Galileo flight-team operations end after the final playback of stored scientific data, months before the spacecraft's planned Jupiter impact.

Galileo is deliberately sent into Jupiter to prevent possible contamination of Europa.