Galileo

Galileo

full name Galileo Galilei. 1564--1642, Italian mathematician, astronomer, and physicist. He discovered the isochronism of the pendulum and demonstrated that falling bodies of different weights descend at the same rate. He perfected the refracting telescope, which led to his discovery of Jupiter's satellites, sunspots, and craters on the moon. He was forced by the Inquisition to recant his support of the Copernican system

Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005

Galileo

(gal-ă-lee -oh, -lay -) A NASA mission to Jupiter and its moons, launched Oct. 18 1989 from the space shuttle Atlantis. With insufficient power to fly directly to Jupiter, Galileo first followed a circuitous 3-year flight path through the inner Solar System using the gravity of the celestial bodies it passed to catapult it on its way. Its trajectory involved the following events: Venus flyby (Feb. 1990), Earth flyby (Dec. 1990), flyby of asteroid (951) Gaspra in the inner asteroid belt (Oct. 1991), second Earth flyby (Dec. 1992). Its instruments sent back excellent images and data on Venus, the Moon, Earth, and Gaspra. The mission received a potentially disastrous blow when Galileo's communications system was crippled after its main transmission antenna failed to open properly in Apr. 1991. As a result, data could be relayed to Earth only using a slow weak backup link, greatly reducing the number of transmitted images. Despite this problem, the spacecraft was to prove a major success.

Following the second Earth flyby, Galileo had gained sufficient momentum to reach Jupiter (see gravity assist). On its flight there, it flew past the asteroid (243) Ida (Aug. 1993), where it discovered the first asteroidal moon, Dactyl, about 1.5 km in diameter, orbiting its primary at a distance of about 100 km. Galileo reached Jupiter in Dec. 1995, entering a 198-day, highly elliptical orbit around the gas giant. Among its first tasks was to relay data back to Earth from a probe it had released in 1995. The probe plunged into Jupiter just as Galileo entered orbit and sent back information on the physical and chemical nature of the upper reaches of the planet's deep atmosphere before being destroyed.

Galileo's mission to the Jovian system was at first set to run for 23 months. During this first period – its primary mission – the spacecraft made observations of Jupiter and flew by the Galilean satellites Ganymede, Callisto, and Europa. It also returned long-range images of the volcanically active Io. Its endurance in the hostile radiation-filled environment around Jupiter and the excellence of the scientific data it sent back to Earth despite its communication problems persuaded NASA to prolong its stay after the end of its primary mission in Dec. 1997. It embarked on extended observations of Europa and Io. In 1999, it made its first close encounter with Io, returning during this and later visits valuable data on the satellite itself and on the Io torus, the doughnut-shaped cloud of highly energetic charged particles that surround the satellite's orbit. In late 2000, Galileo teamed up with the Saturn-bound Cassini–Huygens spacecraft to investigate the interaction between Jupiter's magnetosphere and the solar wind. The Galileo spacecraft remained operational in Jupiter's vicinity for nearly 8 years. In all, it made 35 circuits of Jupiter and completed 34 flybys of its major satellites. It returned a rich stream of information that transformed our understanding of the giant planet itself as well as its retinue of moons and its dusty rings. Altogether, it spent almost 14 years in space, traveling a total distance of 4 631 778 000 km. On Sept. 21 2003, Galileo was deliberately guided into Jupiter's atmosphere to be crushed out of existence.

Collins Dictionary of Astronomy © Market House Books Ltd, 2006

galileo

[‚gal·ə′lē·ō]

(mechanics)

gal

McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

Galileo

(1564–1642) Italian mathematician, astronomer, and physicist. [Ital. Hist.: EB, IV: 388]

See: Astronomy

Allusions—Cultural, Literary, Biblical, and Historical: A Thematic Dictionary. Copyright 2008 The Gale Group, Inc. All rights reserved.

Galileo

["Galileo: A Strongly Typed Interactive Conceptual Language", A. Albano et al, ACM Trans Database Sys 10(2):230-260 (June 1985)].

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Galileo

A satellite-based radio navigation system initiated by the European Union and European Space Administration (ESA). Using 24 satellites and six spares, Galileo was designed to interoperate with the U.S. GPS and Russian GLONASS systems. The first Galileo test satellite (GIOVE-A) was launched in late 2005, and the initial system went live in 2016. With 22 active satellites as of 2020, positioning accuracy is one meter (GPS is 20m; GLONASS is 60m). For more information, visit http://esa.int/Applications/Navigation/Galileo. See GNSS and GPS.

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