GSOC responsibilities include not only mis-sion preparation, acquisition, rocket operations, and payload administration, but also the development of software support systems for mission
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geostationary orbit Atype of orbit that is timed with
the movement of the body it is orbiting so the period
is equal to the average rotational period of the orbited
body If, in addition, the orbit is circular, the satellite
will appear to be not moving when viewed from the
ground, hence the name
Insimpler terms, ifyou place a satellite in a circular
orbit at about 35,900 to 42,164Ianfrom the ground,
it will appear to remain in the same place because of
its synchronized relationship to the EaIth's orbit This
type of orbit has some advantages for
communica-tions The satellite is always available at the same
location and not many high altitude satellites are
needed to provide global coverage The main
disad-vantage is that powerful sending and receiving
sta-tions are needed to send and receive signals to/from
such a high orbit Geostationary orbits were described
by ArthurC.Clarke in the 1940s and 1950s in
con-siderable detail and with remarkable foresight Also
called geosynchronous orbit and fixed satellite orbit.
Geostationary Orbit
In a geostationary orbit, the movement ofthe
satel-lite keeps pace with the movement ofthe Earth and is
thus within the same general visual and
communica-tions region at all times, as seen ji-om the Earth.
geosynchronous orbit See geostationary orbit
GEOTAIL AJapanese research satellite launched in
1992 to study the structure and dynamics of the tail
region of the Earth's magnetosphere The orbit of the
satellite was planned so it would cover the
magnetotail over a wide range of distances It
con-tains instruments to measure the magnetic field, the
electric field, plasma, energetic patticles, and plasma
waves http://www.gtl.isas.ac.jp/
German Space Operations Center GSOc A
com-plex located near Munich, Germany, that was
origi-nally established to support the first German research
satellite (AZUR), launched in 1969 GSOC is a
fa-cility of the German Space Missions Directorate
(DLR) that prepares and executes national and
inter-national cooperative space flight projects through the
main facility and a number ofremote satellite ground
stations GSOC responsibilities include not only
mis-sion preparation, acquisition, rocket operations, and
payload administration, but also the development of
software support systems for mission support, data
handling, and ground operations
One of the interesting experiments undertaken by GSOC and its associates is the GPS Small Satellite Mission Equator-S (launched in 1997) Before this mission, Global Positioning System (GPS) receivers could be used only in near-Earth regions, well below the orbiting height of the GPS satellites themselves This experiment successfully demonstrated that GPS receivers could be used at altitudes up to 34,000 ki-lometers http://www.gsoc.dlr.de/gsoc.htm germania A short name for germanium oxide See germanium
germanium Germanium is a "semi-metal" substance discovered in the I880s It is obtained primarily as
a byproduct of zinc refining There are reports that germanium may slightly convert transverse waves to longitudinal waves and vice versa Materials with conversion capabilities are useful for semiconductor design
The primary use for germanium is for fiber optic sys-tems, and infrared optics account for another 13±2% ofthe market Germanium chloride (GeCI4)is one of the chemicals that may be used in modified chemi-cal vapor disposition (MCVD) processes for creat-ing preform blanks for pullcreat-ing optical fibers
Inpioneer vapor deposition fiber preform fabrication
at Coming, germanium tetrachloride was used to form germanium oxide See fiber fuse effect, va-por deposition
GETS See Government Emergency Telecommuni-cations Service
GFP See global function plane
GFC See generic flow control
GGP See Gateway to Gateway Protocol
ghost I A shadow image on a monitor with phos-phor bum-in When a phosphos-phor-coated display device continually displays the same image (especially if it
is a bright one) an undesirable pale image that does not disappear when the screen is refreshed may be burned into the display surface, thus interfering with the display of desired images This ghost image in-dicates permanent damage to the monitor (unless the coating is replaced) See screen saver 2 Inaudio communications, a quieter repeat or echo of a con-versation 3.In optics, a light-caused image in the dispersion plane resulting from periodic ruling errors
in a diffraction grating (as opposed to scattering errors) ghost, broadcast In broadcast images on a television screen, a slightly offset, pale copy of the desired im-age caused by secondary transmission of the origi-nal sigorigi-nal Terrain can cause reflections of the direct signal that arrive at the receiver just slightly delayed and make the image appear slightly blurred or double ghost port In the early days of computing, software was in its development stages and was not always written to handle processes in a secure manner Thus, when users left a system or terminated a remote con-nection in an unexpected way, the process itself did not necessarily terminate, allowing the next user into the currently open account or process It would some-times allow some-timeshare users, for example, to log in
to the previous user's account through the ghost port (the unterminated session) and access the files
Trang 2erating systems and more security-savvy
program-mers developing the software, but hackers are still
sometimes aware ofsecurity holes and programs and
methods that create ghost port access to less robust
systems The phrase can also refer to an access port
to a computer system that is visible to technical
us-ers but invisible to nontechnical usus-ers, in other words,
one accessible through system commands or
proce-dures that are inherent to the system (as opposed to
being hacked into the system) but not generally
known outside of techie circles Thus, ghost port
re-fers to a port that is left behind and is mistakenly
as-sumed to be a new port or one that is visible or
ap-parent only to a subset of computer users
GhostscriptA PostScript graphics language that is
part ofthe Free Software Foundation's GNU project
Ghostscript is almost fully compatible with Adobe's
PostScript Ghostscript is a great tool for viewing and
printing PostScript files Adobe PDF readers, freely
available on the Internet, are now beginning to
su-persede the use ofGhostscript for viewing and
print-ing PostScript files on some systems, but
enhance-ments to Ghostscript for PDF compatibility have kept
it alive on others
giant magnetoresistanceGMR Aresistance effect
discovered in the late 1980s by P Gruenberg in
Ger-many andA Fert in France Large resistance changes
were observed in materials comprised ofalternating,
very thin layers of metallic elements when exposed
to high magnetic fields at low temperatures Other
scientists were excited by this discovery and began
to study many different types of materials and
con-figurations of layers to better understand the effect
and to see whether it could be produced without
sub-jecting the materials to very low temperatures ffiM
researchers such as S Parkin took a particular
inter-est in this area ofresearch.Itwas determined that very
thin combinations of nonmagnetic metals between
layers ofmagnetic metals could induce the
nonmag-netic layer to change its orientation Oscillations in
the magnetic alignment were also detected, and it was
noted that resistance was low or high depending upon
whether the layers were in parallel or antiparallel
ar-rangement
GMR research has led to a new category of
super-sensitive hard disk drives and, since this is a general
reproducible effect, no doubt many other practical
applications will be developed See Kerr
magneto-optic effect
.gifThe conventional graphics file name extension
used for CompuServe's proprietary Graphics
Inter-change Format (GIF) raster-format graphics files See
Graphics Interchange Format
giga-(abbrev - G when combined) (pron jig-a) A
prefix for 109or 1,000,000,000 in the SI system One
billion.Incomputing, a giga is 230or 1,073,741,824
(a multiple of 1024) Giga- has long been used in
supercomputing, mainframe, and scientific
applica-tions, but it was relatively unknown in lay language
until the mid-1990s when gigabyte (Gbyte) hard
drives dropped to consumer price ranges It used to
lot of storage In fact, whole community BBS sys-tems used to run on five megabyte drives in the early 1980s Now two gigabyte drives are considered to be average See atto-
gigabitGB (pron jig-a-bit) 1,073,741,824 (230)bits Gigabit EthernetGbE Ethernet networking capa-bilities capable of supporting half and full duplex transmissions at speeds of 1 Gbps (one billion bits per second) Fast Ethernet, the predecessor to Giga-bit Ethernet, is a widely installed international open standard In 1997, the IEEE approved the P802.3ab study group's proposed 1OOOBase-T standard for full duplex Gigabit Ethernet signaling over Category 5 networking systems This approval led to the IEEE 802.3z Working Group ratifying a standard for Gi-gabit Ethernet, in June 1998, that included three physical layer specifications (one for shielded cop-per wire, two for optical fibers)
Gigabit Ethernet was developed because vendors and users wanted the benefits ofa scalable high speed net-work to support existing Ethernet frame and proto-col characteristics to enhance rather than obsolete existing systems Gigabit Ethernet uses the same frame format, media access control, and flow con-trol characteristics as slower Ethernets Gigabit Eth-ernet provides a practical way to set up a backbone for interconnecting Ethernet and Fast Ethernet net-works, and provides an Ethernet upgrade path as the technology becomes cheaper The types of applica-tions that require enhanced Ethernet implementaapplica-tions include scientific modeling, multimedia communica-tions, data warehouse search and retrieval, and oth-ers The most significant competitor to the faster ver-sions of Ethernet is asynchronous transfer mode (ATM)
Gigabit Ethernet is implemented at the physical (PHY) and media access control (MAC) layers It supports the same frame format and size, and carrier sense multiple access with collision detection COSMA/CD) as Ethernet, and Fast Ethernet Quality
of service (QoS) is not inherent in Gigabit Ethernet, which is primarily a high speed connectivity mecha-nism, but is incorporated through other standards RSVP is one way of providing quality through an open standard that can be incorporated into a Giga-bit Ethernet system
Objectives for link distances include multimode fi-ber optic links up to 550 meters, single-mode fifi-ber optic links up to 3 kilometers, and copper-based links
up to 25 meters, and Category 5 unshielded twisted pair (UTP) links up to 100 meters A Gigabit Media Independent Interface (GMII) is also being studied See asynchronous transfer mode, Ethernet, Fast Eth-ernet, Gigabit Ethernet Alliance
Gigabit Ethernet AllianceGEA ACalifornia-based multivendor open forum established in 1996 to pro-mote the development and acceptance of Gigabit Ethernet technology and to actively support and ac-celerate the standards process The GEA supports IEEE activities with regard to the development and ratification of Ethernet standards, particularly the
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High-Speed Study Group, the IEEE 802.3 Working
Group, and the IEEE 802.3z Gigabit Ethernet task
force The group provides technical resources for
implementation and product interoperability In June
1998, it ratified a standard for Gigabit Ethernet See
Gigabit Ethernet http://www.gigabit-ethemet.orgl
Gigabit Interface ConnectorGBIC.Aninterface,
commonly sold as a hub-compatible peripheral card,
used in Gigabit Ethernet uplinks A hub may have
slots for more than one GBIC The GBIC enables an
optical cable to be connected to an appropriate port
by converting electrical impulses into laser light
sig-nals for transmission over a medium such as Fibre
Channel It is sometimes also called a Gigabit
Inter-face Converter See Gigabit Ethernet
Standardized Cabling Specifications
Specification Description
1000BASE-CX Wire-based transceivers or
physical layer(PRY)devices for short-haul shielded copper cable connections up to 25 meters
1OOOBASE-T Wire-based transceivers of
physical layer(PRY)devices for four-pair twisted-pair copper cable connections up to 100 meters
1000BASE-8X Optical transceivers or physical
layer(PRY)devices for cabling through optical fibers at 770 to
860 nanometer wavelengths
Based upon Fibre Channel signaling for multimode fiber
1OOOBASE-LX Optical transceivers or physical
layer(pRY)devices for cabling through optical fibers at 1270 to
1355 nanometers Based upon Fibre Channel signaling for single-mode or multimode fiber
1000BASE-LH Long-haul multivendor
specification
Gigabit NewsIndustry news on ATM/Gigabit
net-works along with analysis ofcompeting technologies
and market trends, published monthly by
Infonna-tion Gatekeepers, Inc
gigabyteGByte, GB (pron.jig-a-bite) 1,073,741,824
(109) bytes Data rates are often described in
giga-bits per second (Gbps) or, for very fast rates, may be
described as Gigabytes per seond (GBps) Gigabytes
are also used to describe the storage capacities of a
large number of tape and hard drive storage media
Gigabyte System NetworkGSN See Hippi-6400
GIGAMOAgigabyte-class magneto-optical storage
technology developed by Fujitsu Limited and Sony
Corporation, announced in November 1998 It was
the first widely available magnetic-induced super resolution (MSR) technology, providing 1.3 GBytes ofstorage on a 3.5-inch disc with a 5.92 MBytes per second transfer rate GIGAMO retains the same car-tridge size and disc diameter as ISO/IEC15041 stan-dards but has higher linear bit densities The data stor-age capacity is about twice that ofthe widely adopted 640-MByte CD-ROM discs, and the technology is backwardly compatible, using the same write heads
as earlier systems See magnetic super resolution GIGOgarbage in, garbage out.Anabbreviation to describe a situation in which output cannot be better than its corresponding input, with the implication that
it is the fault and responsibility of the developer or data entry person if the system gives back bad or in-complete information See garbage in/garbage out Gll See global information infrastructure
gilbertA centimeter-gram-second (CGS) unit of magnetomotive force equal to 10 divided by 4p am-pere-tum It is named after William Gilbert Gilbert, William(1544-1603)AnEnglish physicist and physician who investigated electrostatic charges
in various substances He observed that magnetized iron lost its attractive power when heated to red heat and publishedDe magnete (On the magnet)in 1600
He emphasized the distinctions between the magnetic effect of substances, such as lodestone, and the at-tractive properties of amber, a distinction previously promoted by 1 Cardan in 1550 but at the time still not widely considered In his treatise, he used the wordelectricato describe attractive phenomena Gil-bert established that the Earth is a large magnet, thus explaining the general behavior ofcompass needles The gilbert unit of magnetomotive force is named after him See gilbert, versorium
GILCSee Global Internet Liberty Campaign Gilder's lawBandwidth capacity will roughly double
in capacity every six or nine months or so This law,
in a sense, takes over from Moore's law, with chip processing capacities doubling about every 18 months to two years With the emphasis away from single user systems towards network technologies, the same general idea is being applied to the growth and evolution ofnetwork transmission technologies The term is attributed to Greg Papadopoulos at Sun Microsystems in honor of George Gilder, a business technology commentator and strong proponent of optical network technologies See lambda switching, Moore's law
Gill, Jonathan "Jock"(ca 1946- ) In 1992, Gill served as a Clinton/Gore campaign consultant on electronic publishing and email access and became the Director of Special Projects in the Office of Me-dia Affairs from 1993 to 1995, during the Clinton Presidential Administration He is probably best known for developing email access to White House documents and, in 1994, being the first manager of the U.S President's Web site, allowing users to take
a virtual tour of the White House and find informa-tion on contacting government agencies Gill is the founder of Penfield Gill, Inc., a media communica-tions and planning company
Trang 4gimbalAmechanism or material that permits an
at-tachment to be freely suspended or inclined in such
a way that the suspended attachment remains level,
or so the attachment can be inclined in any direction
or several directions Marine compasses and
gyro-scopes incorporate gimbal mechanisms
gimpExtremely flexible wire or cable Wire that can
be easily threaded, woven, or spiraled Gimp is
wound up and attached to telephone handsets to
al-Iowa length of wire to tighten up like a spring when
not in use, so the conversant doesn't have to
inter-rupt the phone conversation to reach the refrigerator
Gintl, Julius Wilhelm (1804-1883)AnAustrian
physicist and telegraph director who was one of the
first to propose a practical means to transmit
tele-graphic communications in both directions at the
same time Up to this time, telegraphs were one way,
thus tieing up the lines for returning messages until
the current message was finished Using two
batter-ies and a compensation method, Gintl devised
two-way communications in 1853 Two-two-way or duplex
te-legraphy was an important means of increasing line
capacity that was later refined and extended by other
inventors See duplex telegraphy
Ginzton, Edward Leonard(1915-1998) A
Ukrai-nian-bornArnerican inventor and professor who
emi-grated to San Francisco in 1929, Ginzton headed up
the Microwave Laboratory at Stanford He developed
further applications with the Klystron technology
developed by the Varian brothers, the co-founders
with Ginzton ofVarian Associates, in 1948.In the late
1950s, he headed up the Stanford linear accelerator
project.In1959, he became the CEO of Varian
As-sociates, remaining as Chairman until 1984 and
serv-ing on the Board until 1992
Ginzton is remembered not only for his technical
achievements with the Klystron tube and Stanford
linear accelerator, but also for his pioneering
man-agement policies Ginzton was instrumental in
estab-lishing employee incentives and benefits long before
such practices were common or mandatory His
poli-cies aided him in attracting top talent to the firm and
provided a new model for employee relations in the
emerging Silicon Valley community He also chaired
the National Academy of Sciences committee that
advised on the Clean Air Act of 1971 and, with David
Packard, supported the development of
minority-owned businesses
Ginzton has been recognized through numerous
awards, including the IEEE 1969 Medal ofHonor and
induction into the 1995 Silicon Valley Engineering
Council's Hall ofFame When the Microwave
Labo-ratory at Stanford University broadened in focus,
around 1970, it began to be called the E.L Ginzton
Laboratory It is an independent lab for engineering
and physics research See Klystron, magnetron,
Sili-con Valley, Varian Associates
Giorgi SystemA system of measurement in which
the units are meter, kilogram, second, and ampere
(MKSA)
GIPSee Global Intemet Project
Gisborne, Frederic Newton (1824-1892)An En-glish-born Canadian inventor who devised new ways ofinsulating communications cables against harsh en-vironments With the financial backing ofAmericans, most notably Cyrus Field, Gisborne was a strong motivational and administrative force in linking Eu-rope and North America, in 1858, with the first cessful transatlantic telegraph cable and the first suc-cessful permanent cable a few years later
Leading up to this important historical achievement, Gisbome studied telegraphy in Quebec in the 1840s, excelling in his courses and subsequently accepting
&~~:~:;~;:;~!~~~~J~:~~;£~t~J~~ •• (BNAETA) and, on its behalf, negotiated
unsuccess-fully with eastern Canadian governments to set up a Halifax-to-Quebec telegraph line Thereafter, Gisbome took the position of superintendent of the Nova Scotian telegraph lines He sought backing from the government for an underwater line from Halifax
to Newfoundland, expressing an interest in solving the problems associated with undersea installation and maintenance.In1851, the Nova Scotia Electric Telegraph Company was established to oversee ex-isting lines and create new ones
In 1852, Gisbome left his position with the Nova Scotia Electric Telegraph Company to establish the Newfoundland Electric Telegraph Company His as-sociation with financier Cyrus Field began in 1854 when Gisborne contacted Cyrus' brother, Matthew D
Field, on behalfofthe financially stressed Newfound-land telegraph project The American collaborators purchased the assets of the Newfoundland Electric Telegraph Company and settled its debts, traveling the difficult wilderness journey to St Johns, New-foundland in spring 1854, to present the charter for a proposed New York, Newfoundland, and London Telegraph Company The first undertaking ofthe ex-panded venture was to link Newfoundland with neighboring regions and with the U.S Thus, subma-rine cables were installed between Cape Breton, New-foundland, and Prince Edward Island, and telegraph lines were installed across the perilous Gulf of St
Lawrence (though not on the first try)
With the involvement of the U.S collaborators, who envisioned oceanic telegraphy, Gisbome's ambitions increased He became determined to establish a cable between Canada and Ireland Despite months of harrowing travel and political arrangements further aggravated by financial difficulties, Gisbome contin-ued to pursue his goal of establishing a transatlantic cable Gisbome's contribution is sometimes over-looked, as he pulled out of the partnership near its successful completion, due to distrust and disagree-ments with his collaborators, but he wasan impor-tant contributor, both to the inception and progress
of the project See Field, Cyrus West; Gooch, Daniel;
gutta-percha; transatlantic cable
GITSGovernment Information Technology Ser-vices
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Gladstone-Dale law The refractive index of a
sub-stance varies with a change in temperature or volume
according to a formula in which the index of
refrac-tion(n)plus one, over the density(r),equals a
con-stant(k).
glass A strong, brittle substance primarily composed
of silica, that ranges from transparent to opaque,
de-pending upon the quantity and composition of other
materials contained within the material Impurities
can affect the color, opacity, polarizing and
transmit-tance characteristics, index of refraction, strength,
flexibility and other properties of glass The glass in
jars and windows typically contains about 75% silica
combined with a number of oxides to enhance the
fabrication properties of the glass
Pure glass is generally preferred for fiber optics
com-munications components (e.g., the conducting core),
but impurities may be "doped" into the fiber to alter
its refractive index or selective transmittance of
cer-tain wavelengths There are special challenges
asso-ciated with pulling out long filaments ofpure glass
For example, the process itselfmay introduce bubbles
or a crystalline structure within the glass, which
would interfere with light transmission The addition
of oxides to enhance the fluidity of the glass is not
practical because it introduces undesired impurities
It has been discovered that pulling fibers or fiber
pre-forms at 0 gravity results in a fine, pure glass
with-out the problems of crystallization associated with
Earth-based fabrication See pulling fiber, vapor
deposition
glass housecolloq. A term to describe the large,
glassed-in, controlled environments used to house
and protect (and in some cases air-condition) large
computer installations These environments still
ex-ist, to some extent, in supercomputing systems, but
technological advances have decreased the size and
fragility ofmany computers, and glass houses are no
longer needed for small- or medium-sized
comput-ing systems Glass houses or clean houses are still
used in chip manufacturing environments to provide
a carefully regulated environment where temperature,
humidity, and even tiny particles can affect the
struc-ture and functioning ofcertain delicate or
micromin-iature components
glass insulator Ahistoric utility pole insulating safety
device ranging in size from about 6 inches to about
18 inches that was very commonly used to support
live wires on utility poles See insulator, utility pole
for a chart and more detailed information
glitch 1 Unexpected, small, but annoying problem,
usually causing a delay or minor informational error
This term is usually applied in instances where
rep-etition ofthe problem is unlikely or infrequent 2
Un-desirable brief surge or interruption of electrical
power
Global Area Coverage GAC One ofthe sample data
set archives ofthe National Oceanic and Atmospheric
Administration (NOAA) derived from the Advanced
Very High Resolution Radiometer (AVHRR) sensors
onboard TIROS andNOAA-xsatellites As the
sat-ellites orbit, they collect Local Area Coverage data,
which is stored, combined, and compressed into GAC, available for download
In order to compress the data from LAC to GAC lev-els, four pixels in a scanline are sampled and aver-aged and the fifth pixel is skipped, with the process repeating to the end of the scanline The following two scanlines are then skipped, thus creating a pat-tern for each three scanlines on through the data file GAC resolution is approximately 7.6 km
Various agencies distribute data products based on GAC downloads For example, the SeaWiFS GAC Level 1 consists of radiance data from combined north-to-south scan swaths with file sizes ofabout 19 MBytes SeaWiFS GAC Level 2 is taken from Level 1A data that has been further processed, calibrated, and corrected Unusual conditions may also be marked within the data The National Science Foun-dation, the Office of Naval Research, and other or-ganizations have provided support to a number of research and educational associations for GAC data See Advanced Very High Resolution Radiometer global area network GAN A network that is acces-sible to most or all nations in the world The Internet
is the closest thing we have to a GAN, although it is not yet ubiquitous or accessible by all nations or people
Global Atmospheric Research Program GARP A program in the 1970s to study atmospheric trends and patterns and to extend the range ofdaily weather fore-casts over a longer period than was previously pos-sible The GARP Atlantic Tropical Experiment (GATE) was the first major experiment in the GARP, carried out in 1974 GATE is ofinterest, not only be-cause it was international in scope, but bebe-cause it in-volved intercommunication among a host ofresearch ships, aircraft, and communications buoys.Inthe late 1970s and early 1980s, NOAA meteorological
satel-Iites were designed and launched to support the GARP NOAA-7, for example, launched in 1981, had sensors for measuring the Earth's atmosphere, sur-face, and cloud patterns The GOES system of sens-ing satellites also form part ofthe GARP See GOES Global Atmosphere Watch GAW AUnited.Nations Commission for Atmospheric Sciences monitoring and assessment program that uses technology to track pollution, ozone, and other aspects of atmosphere composition around the world
Global Business Communications Systems GBCS
AnAT&T business, which was rolled in with the AT&T Laboratory restructuring ofBell Laboratories
in 1995-1996, along with the Network Systems Group, AT&T Paradyne, Microelectronics, and Con-sumer Products GBCS is moving into the area of multimedia and secure telecommunications selVices Products include a Unix-based selVer that works on
a private branch exchange (PBX) to provide video-conferencing capabilities over data networks such as Ethernet and mM Token-Ring The selVer software
is called Multimedia Communication Etchange (MMCX) and was implemented first on Unix sta-tions, with the intention ofporting it to PC operating systems
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the Goddard Space Flight Center (GSFC) Global
Change Data Center The GCMD includes both
na-tional and internana-tional remote-sensing data sets
con-tributed by more than 800 U.S and worldwide
orga-nizations, including NOAA, NASA, DOE, NSF,
EPA, USGS, educational institutions, and others.It
is of interest to anyone interested in planet change,
particularly climatic change The data includes
tem-poral and geographic information and some parts are
interlinked with relevant external information The
GCMD relational database is now searchable online
through the GCMD Web site The data is
ofparticu-lar interest to climatologists, agriculturalists,
hydrog-raphers, mineralogists, and others
http://gcmd.gsfc.nasa.gov/
Global Data Processing SystemGDPS A system
ofpreparing and disseminating cost-effective
meteor-ological analyses and forecasts The GDPS retrieves,
assesses; decodes, sorts, and analyzes the data in
pre-paring for making it available for distribution
GDPS is one of three integrated core components of
the World Weather Watch (WWW) system It is
ad-ministrated by the World Meteorological
Organiza-tion GDPS data are valuable for weather
forecast-ing and meteorologically related agriculture,
clima-tology, and aeronautics industries See Global
Ob-serving System, Global Telecommunication System
http://www.wmo.chlweb/www/DPS/gdps.html
Global Development Gateway GOG A major
World Bank initiative proposed through the GOG
Principles discussion forum hosted by Bellanet The
GDG is sponsored by the World Bank to promote
in-formation exchange, access, and development
global directoryAninternetwork computer database
that stores various types ofinformation related to the
various networks The information may be user login
names and passwords, shared database resources,
group member lists, device directories that can be
ac-cessed by more than one network, or pointers to
ous applications or documents common to the
vari-ous networks The Internet has a number of global
directories of file databases, archives, etc See
Go-pher, Archie, Veronica
Global Environmental Monitoring SystemGEMS
Administrated by the United Nations Environment
Programme (UNEP), GEMS was established as part
of the Earthwatch program in 1975 to support and
strengthen environmental monitoring in participating
countries and to improve the collection and
evalua-tion of environmental data Computer-acquired and
-processed infonnation is an important part of this
effort See Global Resource Information Database
global function planeGFP.Anarchitecture within
which the modular functionality for Intelligent
Net-work (IN) services may be globally constructed The
GFP functions are described as service-independent
building blocks (SIBs) The IN is viewed as a single
entity within the GFP GFP is defined in ITU-T
Q.1201 which describes a generic IN GFP model,
service-independent building blocks, and services and
Global Incident Analysis CenterGIAC A SANS Institute center that creates and disseminates reports
of malicious activity on the Internet submitted by system administrators and network security profes-sionals worldwide GIAC maintains a large archive ofsecurity-related papers available for free download http://www.sans.org/giac.htm
global information infrastructureGIL Aterm used since the mid-1990s by international standards com-mittees with regard to goals, standardization, and de-velopment ofglobal interconnected telecommunica-tions systems, including the technology, applicatelecommunica-tions, and related services
Global Information Infrastructure Commission GIIC.Anindependent, nongovernmental initiative inaugurated in July 1995 to promote leadership in the private sector and cooperation between private and public sectors in developing information selVices and networks GIIC fosters economic growth, education, and quality of life through activities suchlas devel-oping an accessible and diversified global informa-tion infrastructure The GIIC operates as a project of the Center for Strategic and International Studies (CSIS) CSIS is a U.S.-based private organization founded in 1962 to conduct research in global public policy
http://www.giic.org/ http://www.csis.org/
Global Internet Liberty Campaign.Ahuman rights group that includes the American Civil Liberties Union (ACLD), the Electronic Freedom Foundation (EFF), and other member organizations
Global Internet ProjectGIP Aprivate sector orga-nization founded in 1996, consisting of senior level managers representing global software and telecom-munications industries with high stakes in Internet development As part ofits activities, GIP encourages the education ofworld decision-makers in the poten-tial evolution and uses of the Internet
http://www.gip.org/
Global Land Information SystemGLIS.An inter-active database system developed by the U.S Geo-logical Survey (USGS) It provides data that is valu-able in the study ofthe Earth's land surfaces Samples and information about GLIS products are available online Topics within the GLIS database include cli-mate, geology, hydrology, land cover, and others There are aerial photographs, satellite images, and digital line graphs to serve a variety of needs The aerial photographs, for example, include sources such
as the National Aerial Photography Program, Na-tional High Altitude Photography, and various radar systems http://www.earthexplorer.usgs.gov/ Global Maritime Distress and Safety System GMDSS A maritime safety system which incorpo-rates automated distress calls using Digital Selective Calling (DSC) In the late 1970s, maritime experts began to develop systems for updating safety and dis-tress communications, resulting in the 1979 draft of the International Convention on Maritime Search and Rescue GMDSS advocates a global search and res-cue plan and a Global Maritime Distress and Safety
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System (GMDSS) as a communications
infrastruc-ture for the overall plan The system is based upon a
combination of Earth-based and satellite-based radio
services, emphasizing ship-to-shore marine signaling
through relatively user-friendly consoles GMDSS
signaling is quickly superseding the decades-old
Morse code-based system In addition to the
automa-tion of distress signals, it calls for the shipboard
downloading ofmaritime safety information as a
pre-ventive measure
In 1996, the Telecommunications Act was written to
encompass U.S marine vessels, and ships were
re-quired to install GMDSS equipment by I Feb 1999
All vessels subject to Chapter IV of the Safety ofLife
at Sea (SLOAS) convention must be fitted with
GMDSS equipment (with stipulated exceptions) as
must mobile offshore drilling units (MODUs)
Implementation of GMDSS has not been without
problems It has been criticized for false alarms and
general reliability problems, and many nations have
been slow to adopt the system See COSPAS/
SARSAT, NAVTEX
global mobile personal communications services
GMPCS A phrase coined by the ITU-Ttodescribe
mobile communications through low Earth orbit
(LEO) satellite systems but later broadened to include
other modes ofmobile communications
(geostation-ary FSS, MSS, "Little LEOs" and wideband LEOs)
GMPCS was the discussion theme of the World
Tele-communication Policy Forum (WTPF), resulting in
a set of principles and recommendations described
inthe "WTAC Report to the Secretary-General [of
the ITU-T] on GMPCS," January 1996
Global Navigation Satellite System GLONASS,
GNSS A satellite system deployed by the Russian
Federation defense department, which has much in
common with the American Global Positioning
Ser-vice (GPS) in terms of satellite placement and the
types of information transmitted The 24 GLONASS
system satellites are orbiting in three planes Unlike
the GPS system, GLONASS claims to plan to use the
same levels of signals for civilian (CSA) and
gov-ernment use (SA), and civilian use is guaranteed for
about the next decade By the late 1990s, the project
had been divided into two stages: (I) GNSS-I, the
first generation Russian GLONASS and U.S GPS
system and (2) GNSS-2, the second generation
sys-tem including civil access with improved
position-ing and services
The MIT Lincoln Laboratory conducts research on
the GLONASS system and reports progress and
ob-servations on the project on their Web site
http://vega.atc.ll.mit.edu/glonass/
Global Network Navigator GNN AWeb-based
in-formation service providing lists of and inin-formation
about new services, sites, and related resources on the
Internet
Global Observing System GOS A system for
ob-taining standardized observations of the Earth's
at-mosphere and ocean surfaces from ground, sea, air,
and space-based observation platforms GOS is one
of three integrated core components of the World
Weather Watch (WWW) system and is administrated
by the World Meteorological Organization GOS data are valuable in weather forecasting and meteorologi-cally related agriculture, climatology, and aeronau-tics Space data are available through the Environ-mental Observations Satellite (EOS) system com-prised of five near-polar and five geostationary en-vironmental observation satellites with a variety of imaging and sounding sensors See Global Telecom-munication System, Global Data Processing System http://www.wmo.ch/web/www/OSY/GOS.hrml Global OneAninternational commercial joint ven-ture of Sprint, Deutsche Telekom, and France Telecom
Global Online Directory GOLD A commercial product from VocalTec that works in conjunction with their Internet Phone software Internet Phone lets you plug a microphone into your personal computer and use it as a phone transmitter to communicate with an-other person with Internet Phone capabilities The computer speaker provides the equivalent of the phone receiver Long-distance calls can be placed as though they were local calls through your ISP, with-out long-distance charges
Internet Phone connections are full duplex, connect-ing through the TCP/IP transport protocol In addi-tion to the features ofa convenaddi-tional phone call, chat lines and other digital enhancements are available GOLD is the global directory that stores information about Internet Phone users who can be contacted, just
as the names of phone subscribers can be accessed through a phone directory
Global Ozone Monitoring Experiment GOME A satellite-borne ozone European Space Agency (ESA) research project launched in April 1995 on board the European Remote Sensing Satellite (ERS-2) GOME
is a nadir-viewing passive spectrometer that senses atmospheric trace constituents by measuring solar ra-diation scattered by Earth's atmosphere Cloud char-acteristics, aerosols, and surface reflection can also
be measured GOME is designed to sense in the vis-ible and ultraviolet spectra from 240 to 790 nanom-eters See GOME Data Processor
http://auc.dfd.dlr.de/GOME/
Global Positioning System GPS A space- and ground-based 24-hour navigational system originally designed and used by the U.S military (see Navy Navigation Satellite System), funded and maintained
by the U.S Department ofDefense (DoD) It provides the means to monitor, update, and maintain orbiting satellite systems and to determine a location on or around the Earth through information from these sys-tems
GPS uses the known positions of satellites as refer-ence points for discerning unknown positions on or above the Earth There are now over 20 satellites in the system (some are spares), more-or-Iess evenly spaced, orbiting in 12-hour cycles at an altitude of about 10,898 miles (about 400 miles higher than the original NNSS) A system of sophisticated ground stations with antennas, coordinated by a master con-trol station, administers, deploys, and maintains the
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A variety of types of information can be computed
from information from several satellites, including a
location or position ofa stationary or moving object,
and coordination oftime This information can be
in-corporated into software applications in
vehicle-mounted or handheld positioning receivers From
military operations, to recreational navigation on the
ocean in a kayak, to airline navigation, GPS provides
a wealth ofdata with which to determine latitude and
longitude, altitude, and velocity This information can
further be combined with maps to record or suggest
routes
GPS satellites transmit timed binary pulses in
addi-tion to informaaddi-tion constants about the current
loca-tion of the satellite The synchronized atomic clocks
aboard the satellites permit the transmission of
pre-cise timing tags The combination of the speed of
transmitted electromagnetic waves and the atomic
clocks installed in GPS satellites provides remarkably
accurate timing pulses
NAVSTAR Global Positioning System
NAVSTAR Global Positioning System (GPS)
litefrom the 24-unit constellation ofplanes and
satel-lites thatprovides military and civilian navigation and
positioning data The nine-ton satellites orbit the Earth
every12hours, emitting continuous positional
sig-nals The signals can be used to calculate time,
loca-tion, and velocity, depending upon the capabilities of
the GPS receiver The system is controlled and
oper-ated by the 50th Space Jfing out of Schriever AFB,
Colorado {U.S Air Force Space Command image.]
The GPS Master Control Station (MCS) is operated
by the 50th Space Wing's 2nd Space Operations
Squadron in Colorado This squad is responsible for
monitoring, controlling, and operating the GPS
sat-ellite constellation The u.S Air Force Space
Com-mand Space and Missile Systems Center in Los
An-geles, California, is the executive agent for the
De-partment ofDefense(000)acquiring GPS satellites
and equipment
There are thousands of GPS users worldwide
Per-sonal GPS devices can be purchased for as little as
in all industries that rely on location information: air-lines, shipping fmns, ferries, military divisions, etc For greater details on individual aspects ofGPS, see differential GPS, EAGLE, Intelligent Vehicle High-way Systems, GPS Operational Constellation, GPS Navigation Message, local differential GPS, NAVSTAR, Precise Positioning Service, Standard Positioning Service, wide area differential GPS
Global Resource Information Database GRID A
global network of environmental data centers coop-erating to generate and disseminate key environmen-tal geo-referenced and statistical data sets and infor-mation products GRID centers are equipped to pre-pare, analyze, and disseminate environmental data that may be used as the basis for environmental as-sessments GRID is associated with the Earthwatch program and the Environment Assessment Division
of the United Nations Environment Programme (UNEP) It was established in 1985, evolving gradu-ally out of the 1972 United Nations Conference on the Human Environment held in Sweden Following the conference, UNEP was created to provide a fo-cus for a Global Environment Monitoring System (GEMS) that led to GRID
There are a number of GRID centers around the world, including in the U.S., South America, Europe, Russia, Nairobi (UNEP headquarters), Asia, and New Zealand For example, the United Nations Environ-ment Programme (UNEP) and 1987 World Commis-sion on Environment and Development project in cooperation with the Government ofNorway estab-lished a GRID environmental information center in Arendal, Norway GRID-Arendal was opened as a nonprofit foundation in August 1989; it communicates and cooperates with other GRID centers
Global Software Defmed Network GSDN
Ahigh-volume commercial virtual private network service from AT&T that utilizes AT&T's Worldwide Intelli-gent Network (WIN) to interconnect networks in the U.S and other countries GSDN selects an economi-cal route for external economi-calls and provides internal ser-vices, including order entry, tracking, file transfers, and teleconferencing services GSDN is aimed at business networks
Global Standards Collaboration GSC A
frame-work for the exchange ofinformation regarding glo-bal standards development for interconnectivity and interoperability of systems and devices Thus, the GSC has been bringing together senior officials from regional, national, and international standards bod-ies since 1988 Participating bodbod-ies include the ternational Telecommunication Union (ITU), the In-ternational Organization for Standardization (ISO), the European Telecommunications Standards Insti-tute (ETSI), and others Focal areas are discussed at large conferences For example, global radio stan-dardization was the key topic for the 2000 meeting
in Sapporo, Japan Other topics ofcurrent interest in-clude number portability for mobile communications, universal personal telecommunications (UPT), and intelligent networks http://www.gsc.etsLorg/
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Global System for Mobile, Groupe Speciale
Mo-bile GSM A digital cellular technology developed
jointly by the telecommunications administrations of
Europe The Groupe Speciale Mobile was founded
in the early 1980s, and the Global System for
Mo-bile (GSM) was first publicly announced in 1991 and
has since been standardized in Europe and Japan
GSM was the first fully digital system to provide
mobile voice connections, data transfer services,
pag-ing, and facsimile at full duplex or half duplex rates
up to 9600 bps GSM operates in two frequency
ranges: 890 to 915MHzfor signaling infonnation and
935 to 960 MHz for information transmissions
GSM is a set ofstandards specifying a digital mobile
communications services infrastructure It is based
on a 900MHzradio transmission technology and
specifies related switching and signaling formats.An
1800 MHz Digital Cordless System (DCS) has also
been added Since mobile systems typically support
roaming, and since the multicultural makeup of
Eu-rope provides a unique challenge in providing
com-patible services, interoperability has been emphasized
in the GSM specifications
GSM can be described in three categories:
commu-nications media, transceiving systems, and
informa-tion systems, as shown in the GSM General
Catego-ries chart
The GSM subscriber identity module (SIM), also
known as a smartcard, is a security feature which
handles encryption and authentication It includes
memory storage which can be used for dialing codes
or other information related to the service The SIM
is also a means to download and display call-related
information See Future Public Land Mobile
Tele-communication System, Personal Communications
Network
Global Telecommunication System GTS Asystem
of terrestrial and space-based data circuits for
inter-connecting meteorological telecommunications
cen-ters GTS is one ofthree integrated core components
of the World Weather Watch (WWW) system and is
administrated by the World Meteorological Organi-zation GTS data are valuable in weather forecasting and meteorologically related agriculture, climatology, and aeronautics The GTS provides rapid and reliable dissemination of observational meteorological data The GTS is organized into a Main Telecommunica-tion Network (MTN), Regional Meteorological Tele-communication Networks (RMTNs), and the Na-tional Meteorological Telecommunication Networks (NMTNs) The World Meteorological Centres (WMOs) are located in Russia, Australia, and Wash-ington, D.C., and there are more than a dozen regional hubs in Asia, South America, Africa, Europe, and other locations See Global Observing System, Glo-bal Data Processing System
http://www.wmo.ch/web/www/TEM/gts.html Global Title Translation GTT Atelephony and ad-ministration and routing function that enables added feature functionality in commercial systems such as Local Number Portability (LNP), calling card ser-vices, and mobile roaming support GTT determines destination addresses in Signaling System 7 (SS7) and other relevant network systems When a call is initiated, GTT detennines the destination and may include additional information, depending on the fea-ture service GTT may support multiple global title addresses
Global Transaction Network GTN AT&T's exten-sive 800 service phone network, which was in-troduced in 1993 This service supports enhanced fea-tures, providing more flexible routing and number-ing services which can be used, for example, by air-line reservation systems
Globalstar A system of 48 small bent pipe
commu-nications satellites orbiting at 1400 kilometers (LEO), for providing voice and data services (data files, pag-ing, facsimile) Globalstar was established in 1991
as ajoint venture ofLoraISpace & Communications, Ltd., QUALCOMM, Inc., and a number ofcorporate partners Launching began in February 1998.In1999, Globalstar launched four more systems, bringing the
Global System for Mobile (GSM) General Categories Category Notes
Media GSM works over frequency-modulated (FM) signals using a combination of time division
multiple access (TDMA) and frequency division multiple access (FDMA) Peak output power varies with the type of transmitter (mobile station class), ranging from0.8to20
watts Frequency hopping is used to reduce interference and multipath fading, and
encryption increases security The data rate is270Kbps
Transceiving There is a base transceiver station (BTS) associated with each cell operating on fixed
frequencies unique to its region Honeycomb-like clusters are handled by base station controllers (BSC), which, in tum, are controlled (routed, switched, handed over) by Mobile Service Switching Centers (MSC)
Information There are databases associated with GSM that aid in the administration of subscriber
information and those that aidinthe administration of security and associated
authentication mechanisms There is also an equipment identity register (EIR), which keeps track of equipment types and configuration, and can block calls on stolen units
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over the next two years
Globalstar services can be accessed with
vehicle-mounted or handheld devices resembling cellular
phones, and the system is integrated with cell phone
services through dual-modem handsets Remote
us-ers can access the system through Globalstar service
providers, with fIXed-position and wireline phones
Globalstar is intended to enhance rather than replace
existing cellular and other phone services Services
are aimed at international business travelers,
commer-cial vehicle operators, marine craft, field scientists,
and others The competitive aim is low cost for
ser-vice and accessories
GLONASSGlobal Navigation Satellite System A
Russian Federation Global Positioning System
simi-lar to the U.S NAVSTAR system GLONASS is
managed by the Russian Space Forces GLONASS
provides all-weather positioning coordinates,
veloc-ity references, and time information from virtually
any point on or near the globe
More specifically, the GLONASS system aids in
managing air and marine traffic, in supporting
emer-gency and safety systems, geodesy, cartography, and
ecological monitoring Like the American GPS
sys-tem, GLONASS is two-tiered It provides standard
precisionnavigation signals (SPs) with horizontal
accuracy to about 63±6 meters and high-precision
navigation signals (HPs) with authorization and
spe-cialized equipment
The GLONASS system has launched more than four
dozen satellites since the first was put into operation
in October 1982 Early satellites had a lifespan of
about two years, while later satellites lasted about four
or five years.Ingeneral, the launches have been
suc-cessful, although in 1987 and 1988 there were a
num-ber of failures Since 1989, the orbiting platforms
have included geodetic reference satellites.In
Feb-ruary 1999, the Russian Federation made an open
declaration of increasing international cooperation
with regard to national satellite navigation
technolo-gies and international navigation systems The
con-stellation status is reported, within a few days, on the
GLONASS Web site
http://www.rssi.ru/SFCSIC/english.html
Glossary of Telecommunications Terms,FCC A
short glossary of telecommunications terms related
mainly to delivery of broadcast services to consumers
provided by the Federal Communications Commission
Glossary of Telecommunications Terms, Federal
StandardOriginally introduced in 1976 as
MIL-STD-188-120, this archive has evolved through
sev-eral revisions to become the Telecom Glossary 2000
It is provided through theu.s.National
Communi-cations System in print, CD-ROM, and Web formats,
with increasing emphasis on electronic development
and dissemination The Glossary is mandated for use
by all federal departments and agencies for the
prepa-ration of telecommunications documentation and is
available from the National Technical Information
Service
and updated by the FTSC Subcommittee to Revise FED-STD-J037B. The subsequent version, FED-STD-l 03 7C (1996), was further updated to Telecom Glossary 2000, with many of the new definitions drawn from TI Standards and Reports
The Glossary includes standard definitions for tele-communications terms related to antennas, comput-ers, transmissions media (e.g., fiber optics), networks, audio/video technologies, radio communications, etc
Sources include government publications and those
of prominent telecommunications organizations in-cluding the lTV, ISO, and the American National Standards Institute
The Glossary has been reviewed by the National Communications System Member Organizations, the Federal Telecommunication Standards Committee members, members ofrelevant industries and federal agencies, and by the general public Telecom Glos-sary 2000 was discussed through members of the TIAI Ad Hoc Glossary Group
GMDSSSee Global Maritime Distress and Safety System
GMDSS Radio Maintainer LicenseA license granted by the Federal Communications Commission (FCC) to maintain radiocommunications aboard ships that are equipped to comply with Global Maritime Distress and Safety System (GMDSS) regulations It further confers the operating authority ofthe General Radiotelephone Operator License and the Marine Radio Operator Permit A licensed maintainer is re-quired by ships that conduct at-sea maintenance The license requires FCC Element 1, Element 3, and El-ement 9 exams to be passed
GMDSS Radio Operator LicenseAlicense granted
by the Federal Communications Commission (FCC)
to individuals deemed capable ofhandling radiomunications aboard ships that are equipped to com-ply with Global Maritime Distress and Safety Sys-tem (GMDSS) regulations The licensee may oper-ate basic equipment and make antenna adjustments
The license further confers the operating authority of
a Marine Radio Operator Permit Applicants are re-quired to pass the Element I and Element 7 written exams
GMPCS See global mobile personal communica-tions by satellite
GMR See giant magnetoresistance
GMS See Geostationary Meteorological Satellite
GMSKSee Gaussian minimum shift keying
GNN See Global Network Navigator
GNOMEAnopen source user software environment and applications framework available to developers
as part ofthe GNU project GNOME is typically dis-tributed with BSD and GNU/Linux distributions and
is available for other platforms as well
The goal of the GNOME project is to provide a user-friendly graphical desktop environment and a devel-oper-friendly base of tools for creating GNOME-compatible software applications to augment or re-place commercial operating systems and develop-ment environdevelop-ments As the project has evolved, it is
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