time Is related to the class of user (Le.
`truck, aircraft, etc.), and can be changed
`by either the user or GEOSTAR Central.
`Thus, the user can get position Informa(cid:173)
`tion at a desired rate while not wasting
`channel capacity.
`
`When not inhibited, users will te(cid:173)
`spond at the uplink center frequency of
`1618.25 MHz with a short burst of 20-80
`milliseconds depending on the size of the
`alphanumeric message. The user re(cid:173)
`sponse will be a spread spectrum signal
`that contains the user's unique ID, proto(cid:173)
`col information, and any messages to be
`sent to or via GEOST AR Central.
`
`The user's response will be "bent(cid:173)
`piped"
`(relayed with no processing)
`through at least two satellites to GEO(cid:173)
`STAR Central where the roundtrip signal
`transit time will be calculated. The time of
`transmission will be measured between
`the Central's transmitter and the user's
`terminal, calculating the time for the user
`to respond via each of two separate satel(cid:173)
`lites, plus the time required for the user's
`terminal to internally process the signal.
`GEOSTAR Central will measure
`the
`roundtrip time by comparing a local rep(cid:173)
`lica of the user's known code with the re(cid:173)
`ceived code and by measuring
`the
`associated time delay. The time delay
`(scaled by the velocity.of light) is related to
`the roundtrip range from GEOSTAR Cen(cid:173)
`tral to the user's transceiver. GEOSTAR
`Central will determine position and may
`transmit it, together with outgoing mes(cid:173)
`sages, to the mobile user.
`
`Benchmarks
`
`will be standard terminals enclosed in an
`environmental shelter. Higher power out(cid:173)
`put and high-gain antennas may be
`employed to enhance benchmark per(cid:173)
`formance.
`
`Known as "differential operation,"
`benchmark employment will eliminate
`many of the ranging bias errors that
`plague other navigation systems, includ(cid:173)
`ing the inherent delay characteristics of
`system electronics. Benchmark correc(cid:173)
`tions can be implemented as either a
`measurement correction or as a position(cid:173)
`ing solution correction. Both methods
`have been demonstrated successfully in
`other differential navigation systems.
`
`The first approach corrects the range
`measurements before the position deter(cid:173)
`mination is performed, with
`the
`true
`ranges to a benchmark calculated using
`the known benchmark, satellite, and Cen(cid:173)
`tral locations. The calculated roundtrip
`distance is compared to the measured
`range to yield the range bias for that area.
`This bias can then be applied to the meas(cid:173)
`ured ranges of the user terminals in the vi(cid:173)
`cinity of the benchmark before the user
`position calculation is performed.
`
`,
`
`The other approach, position solution
`correction, uses the normal positioning al(cid:173)
`gorithm to calculate the position of the
`benchmark
`from uncorrected
`range
`·measurements. This estimated position is
`then compared with the known position of
`the benchmark, and the difference can be
`applied to correct the pOSition locations of
`nearby users. Propagation differences,
`altitude, and atmospheric delays caused
`by weather are also factored in.
`
`The use of fixed "benchmark" (or ref(cid:173)
`erence point) transceivers at known loca(cid:173)
`tions will be an important contributor to
`RDSS. position accuracy. Benchmarks
`
`Differential correction has been
`shown to compensate for range bias er(cid:173)
`rors over a wide area around the bench(cid:173)
`mark. However, uncertainties in satellite
`
`_26 - RDSS- - - - - - -
`
`Page 000032
`
`

`
`ephemeris (orbital location), and iono(cid:173)
`spheric and tropospheric errors of about a
`meter may remain after differential cor(cid:173)
`rection. The atmospheric error varies with
`the distance between the user and the
`benchmark, and is due primarily to slight
`non-uniformities of
`the atmosphere
`above the benchmark and user sites.
`Summarized below are the errors and
`their values in meters that remain after dif(cid:173)
`ferential correction.
`
`In the operational concept for System
`3, benchmarks will be spaced about 100
`miles apart. This will provide position de(cid:173)
`termination with a relative accuracy to ap(cid:173)
`proximately 7 meters of the actual loca(cid:173)
`tion . Where benchmarks are not avail(cid:173)
`able, Geostar will use mathematical mod(cid:173)
`els to help offset the errors inherent in
`pure time difference-of-arrival measure(cid:173)
`ments. Using the differential method, po(cid:173)
`sitioning data can be displayed in more
`detail with reference to the nearest bench(cid:173)
`mark; for example: "user is located 50 me(cid:173)
`ters due west of the southern end of
`runway 4 at Miami Airport, Florida." Plans
`call for an initial fielding of approximately
`100 benchmarks in the United States.
`
`Range Errors
`
`Meters
`
`2.8
`User transceiver noise
`Benchmark transceiver noise 1.4
`Ephemeris (satellite motion) 0.1
`Atmospheric delay
`0.5
`Multipath (signal reflections) 1.0
`
`I Altitude Errors
`
`GEOST AR System 3 will use two
`range measurements combined with a
`
`Benchmarks
`
`>100 Benchmarks Across U.S.
`
`terrain elevation map to locate the posi(cid:173)
`tion of a mobile land USEjr and altimeter in(cid:173)
`formation for the position of airborne
`users. The digital terrain elevation map Is
`located In GEOSTAR Central computers.
`Altimeter
`information
`is automatically
`transmitted to GEOST AR Central for air(cid:173)
`borne users.
`
`Errors in terrain height influence the
`absolute positioning accuracy, but the
`relative accuracy of nearby users is unaf(cid:173)
`fected. This "is particularly true in rendez(cid:173)
`vous or homing applications. If one user is
`trying to reach another user (for example,
`rescuers trying to reach an injured hiker),
`any errors in the terrain map would have a
`diminishing effect on navigational guid(cid:173)
`ance given by the GEOSTAR Central di(cid:173)
`recting the rendezvous.
`
`r - - - - - -___ RDSS_27
`
`Page 000033
`
`

`
`Page 000034
`
`

`
`Near-Global Access Through
`
`The
`Space
`Segment
`
`WHA T SA TELLITES ARE USED TO PROVIDE SERVICE?
`
`Radio determination satellite service
`is provided through the use of space(cid:173)
`based relays, with transponders that
`translate between user terminal operating
`frequencies and those of the Central. In
`this manner, the terminal's L-Band or S(cid:173)
`Band transmit and receive frequencies
`are translated to the C-Band (or Ku(cid:173)
`Band) uplink and downlink frequencies of
`the Central.
`
`Initially, ROSS satellites are planned
`to cover the continental United States;
`
`then, as marketing conditions permit, the
`number of satellites will be expanded to
`include regional coverage on a near
`global basis. Engineering estimates envi~
`sion that a minimum constellation of six to
`eight satellites could establish worldwide
`coverage, except forthe polar regions. If a
`single satellite failed, this constellation
`would still provide 'a backup capability.
`Polar coverage is possible using a suit~
`able satellite host; however, there are no
`plans to furnish such a capability at this
`time.
`
`----RDS
`
`Page 000035
`
`

`
`Geostar satellite,
`22,000 miles above
`the earth
`
`Many satellite launch dates and or(cid:173)
`bital positions for the worldwide constella(cid:173)
`tion remain unconfirmed because RDSS(cid:173)
`licensed member countries and prospec(cid:173)
`tive member countries are still defining
`their specific satellite communications re(cid:173)
`quirements. It is clear, however, that dur(cid:173)
`ing the next several years a family of
`different RDSS satellites will be launched
`and operated by Geostar and other inter(cid:173)
`national licensees. Each satellite system
`will be compatible with GEOSTAR and
`will probably follow a similar fielding ap(cid:173)
`proach: initial installation of specialized
`digital location transmission equipment as
`piggyback payloads on two or three geo(cid:173)
`stationary communications satellites, to
`
`be followed by a family of dedicated
`RDSS satellites.
`
`Due to a setback in the U.S. space
`program, early GEOST AR payloads are
`being launched by Arianespace, the first
`commercial subsidiary to market and sell
`French space systems and services
`worldwide. Rockets are launched from the
`European Space Agency
`facility
`in
`Kourou, French Guiana.
`
`With the resumption of U.S. Space
`Shuttle operations, three GEOST AR pay(cid:173)
`loads are scheduled among the first
`launches of commercial cargo. This com(cid:173)
`mitment is significant in light of the re-
`
`_ 30 -RDSS-------
`
`Page 000036
`
`

`
`structuring of U.S. space program and the
`sharp decline in its support for civilian
`payloads. As a result of the rescheduling
`of the space shuttle, GEOSTAR dedi(cid:173)
`cated satellites are expected
`to be
`launched in October 1991, October 1992,
`and June 1993, but this is subject to
`change.
`
`In the U.S., both RDSS payloads
`launched during 1988 were receive-only
`(RO)
`transponders
`riding piggyback
`aboard host domestic communication sat(cid:173)
`ellites. In 1989, the second satellite will
`reach geosynchronous orbit and be
`added to System 2 to provide an interim
`one-way messaging capability for the
`
`European Space Agency Launch
`Facilities in French Guiana
`
`Caribbean and Central America. Begin(cid:173)
`ning in 1992, both satellites will be aug(cid:173)
`mented by a family of dedicated GEO(cid:173)
`STAR satellites with an enhanced multi(cid:173)
`beam transmit-receive capability that will
`be the mainstay for commercial and
`government applications.
`
`In addition to geosynchronous satel(cid:173)
`lites, GEOSTAR is currently taking ad(cid:173)
`vantage of the polar-orbiting NOAN
`ARGOS satellite system for an interim op(cid:173)
`erational capability with limited applica(cid:173)
`tion.
`
`ARGOS SA TELL/TES
`
`Service ARGOS, a joint U.S. and
`French system, began providing satellite
`data relay services to Geostar in May
`1987. The system comprises two ARGOS
`satellites, identified as NOAA 9 and 10,
`that operate in a medium altitude, circular
`orbit. Historically, ARGOS has been used
`by the scientific community for weather
`observation, animal tracking, and other
`scientific applications. The National
`Weather Service had been the largest
`user of ARGOS; however, Geostar is cur(cid:173)
`rently believed to be the primary customer
`in terms of user terminals. As a precondi(cid:173)
`tion for utilizing Service ARGOS, user
`transmitters automatically report local
`temperature readings.
`
`This introductory one-way capability
`for GEOSTAR is known as System 1 serv(cid:173)
`ice. Traffic is relayed from a mobile user,
`through the satellite, to one of several
`NOANARGOS ground stations located at
`multiple sites around the world. Despite
`system limitations, System 1 service will
`continue to be offered by Geostar after the
`introduction of System 2 (receive-only
`satellite service) as long as there is a user
`demand.
`
`-------RDSS-· _31
`
`Page 000037
`
`

`
`RECEIVE-ONL Y
`SATELLITES
`
`In 1988, two receive-only packages
`were orbited aboard U.S. domestic satel(cid:173)
`lites launched by Ariane. Each package
`contains two ROSS transponders, one
`primary and one backup. With these pack(cid:173)
`ages, Geostar introduced System 2 serv(cid:173)
`ice, a one-way messaging system with an
`external positioning capability. System 2
`is unique in that the user utilizes an exter(cid:173)
`nal position locating service, such as LO(cid:173)
`RAN-C, to
`input data to
`the user's
`terminal.
`
`The receive-only satellite is used to
`communicate data messages from a us(cid:173)
`er's terminal to the Geostar Central. Each
`
`receive-only satellite package is rela(cid:173)
`tively inexpensive and weighs approxi(cid:173)
`mately 36 pounds with antenna.
`
`The dual receive-only packages will
`provide redundant coverage of the Conti(cid:173)
`nental U.S. as well as single coverage
`over parts of Latin America. Each re(cid:173)
`ceive-only package has a capacity of ap(cid:173)
`proximately 1,000,000 user terminals
`(based on an average of one transmission
`each per hour). Two receive-only satel(cid:173)
`lites in different orbital locations are suffi(cid:173)
`cient to optimize radio reception when
`local conditions impair line-of-sight be(cid:173)
`tween the user and satellite. For example,
`if the user terminal's view of one satellite
`is blocked in one direction, access can be
`acquired through the other satellite. Dual
`
`GEOSTAR Receive-Only Satellite Footprints
`
`_32 _RDSS-------
`
`Page 000038
`
`

`
`coverage of the continental U.S. en(cid:173)
`hances system dependability and pre(cid:173)
`cludes a single-point failure. Because the
`represents an
`receive-only package
`add-on capability to the host commercial
`communications satellite, the possibility
`of antenna adjustment to alter or optimize
`RDSS earth coverage is very limited.
`
`The first operational RDSS geosyn(cid:173)
`chronous package, GEOSTAR RO-1,
`was launched aboard the GTE communi(cid:173)
`cations satellite, SpaceNet 3R, by an
`Ariane rocket on 11 March 1988. It was
`placed in geosynchronous orbit at 87 de(cid:173)
`grees West longitude. Specially config(cid:173)
`ured with one 2 x 4 foot flat-plate patch
`array antenna, the RDSS package ac(cid:173)
`quires the 1618.25 MHz L-Band uplink
`frequency received from a user's terminal
`and translates it into Ku-Band (12 GHz)
`for downlink to the Geostar Central facility
`in Washington, DC.
`
`The GEOSTAR RO-2 package was
`launched aboard
`the GTE satellite,
`GSTAR III, in September 1988; its opera(cid:173)
`tional service will begin approximately
`3Q-1989. The geosynchronous orbital
`placement will be 126 degrees West.
`Equipped with two flat plate antennas,
`one will cover the U.S. and the other parts
`of Latin America. The RDSS receive-only
`system will serve about 1 ,000,000 users
`per hour.
`
`TWO-WAY
`COMMUN/CA T/ONS
`
`The Geostar Corporation has accel(cid:173)
`erated plans for two-way service by more
`than one year (mid-1989) through the
`lease of an existing C-Band equipped
`commercial satellite, that supplements
`the one-way System 2 (inbound only)
`with an outbound messaging capability.
`
`Called System 2C, it will have the capabili(cid:173)
`ty to service a potential 1 ,000,000 users by
`obtaining position
`information via
`LORAN-C or other radionavigation
`system, and providing inbound messaging
`on L-Band and outbound messaging on
`C-Band.
`
`DED/CA TED SA TELL/TES
`
`Spurred by the favorable acceptance
`of early commercial service, the Geostar
`Corporation has moved directly into the
`acquisition of dedicated RDSS satellites.
`The dedicated satellite capability will pro(cid:173)
`vide two-way digital message exchange
`and geopositioning services, but with sig(cid:173)
`nificantly greater capacity and lower user
`power requirements than System 2C.
`
`In August 1986, the FCC authorized
`the Geostar Corporation to construct and
`launch a family of four dedicated sat(cid:173)
`ellites, including an on-ground spare.
`Orbital slot assignments also were
`authorized. The active constellation will
`consist of three satellites in orbit providing
`Western Hemisphere coverage.
`
`In late 1987, Geostar Corporation
`awarded a multi-million dollar contract to
`GE Astro-Space Division to construct two
`satellites, with options for the third and
`fourth spacecraft. In mid-1988, an option
`to develop a third dedicated satellite was
`exercised. The 4000-pound dedicated
`spacecraft, known as GEOSTAR DS-1,
`DS-2, and DS-3, will be configured with a
`parabolic dish as much as five meters in
`diameter. The antenna will have an elec(cid:173)
`tronic aiming capability that will form eight
`beams of overlapping coverage for North
`and possibly South America, depending
`on the final beam pattern, which remains
`to be determined.
`
`___ ____ RDSS_33
`
`Page 000039
`
`

`
`signal power into a cluster of eight foot(cid:173)
`prints, each approximately 500- 1000,
`miles in diameter on the Earth's surface.
`The total footprint of the eight beams is to
`be determined; a study is underway to op(cid:173)
`timize coverage of the first dedicated sat(cid:173)
`the continental U.S. and
`ellite over
`Caribbean area.
`
`Technically, the estimated capacity
`for the dedicated satellite is approxi(cid:173)
`mately 5 million users in one spot beam.
`This estimate must be tempered by satel(cid:173)
`lite power limitations, switching limita(cid:173)
`tions, hub design, and computer memory.
`For eight beams, the system capacity is
`approximately 25 million users - nomi(cid:173)
`nally, overlapping beams contribute to a
`corresponding reduction in potential user
`capacity of 20-30 percent. Each beam will
`be assigned a unique beam number (this
`is transparent to the user) and each will
`ride a separate downlink to the Central, as
`necessary, to support traffic for all users
`of a particular beam.
`
`Dedicated Satellite
`Multibeam Coverage
`
`ROSS Satellite Schedule Summary
`
`North
`America
`
`In service since
`May 1988
`
`North
`America and
`Central South
`America
`
`Estimated
`Sept 1989
`
`North
`America
`
`Estimated
`June 1989
`
`Western
`Hemisphere
`
`Estimated
`1991
`
`Western
`Hemisphere
`
`Estimated
`1992
`
`Western
`Hemisphere
`
`Estimated
`1993
`
`The System 3 satellite will have an L(cid:173)
`Band uplink and S-Band downlink to and
`from the user, and a C-Band up and
`downlink to ground control at Geostar
`Central. The latter operates at approxi(cid:173)
`mately 6.5 GHz and 5.150 GHz.
`
`Ground control of the dedicated satel(cid:173)
`lites may be performed by Geostar, or GE
`Astra-Space may be given responsibility
`for tracking, telemetry, and control. Tenta(cid:173)
`tive plans call for a second ground control
`facility to be established on the West
`Coast.
`
`The dedicated satellite will generate
`. multiple overlapping beams that focus
`
`_ 34 -RDSS-------
`
`Page 000040
`
`

`
`System capacity of the dedicated sat(cid:173)
`ellite is constrained by the number ·of
`transmit/receive beams formed. This limit
`is imposed by the channel bandwidth.
`Some 66 MHz of S-Band bandwidth was
`allocated to support four 16.5 MHz wide
`channels. Use of antenna polarization
`techniques effectively doubles the num(cid:173)
`ber of spot beams from four to eight, as
`authorized by the FCC and the ITU.
`
`It is important to note that the ITU did
`not authorize or approve other techniques
`to expand the downlink. The System 3
`dedicated satellite has more antenna gain
`and transmitting power than the System
`2C satellite: an effective isotropic radiated
`power of 52 dbw versus 47 dbw. Hence,
`the dedicated satellite is capable of twice
`the data rate and double the number of
`potential users (per beam). This equates
`to many times more users than System
`2C, and the dedicated satellite system will
`provide better performance.
`
`RDSS INTERNA TIONAL
`SATELLITES
`
`In the interest of establishing a world(cid:173)
`wide ROSS system, the Geostar Corpora(cid:173)
`tion is seeking to consummate licensing
`agreements with
`international clients,
`principally governmental and civil com(cid:173)
`munications (post telephone and tele(cid:173)
`graph - PTT) organizations. More than 70
`countries have been contacted in an effort
`to influence the integration of ROSS with
`the second generation of domestic and re(cid:173)
`gional commercial satellites being fielded
`around the world. As new ROSS systems
`come on line, they are expected to be inte(cid:173)
`grated into a global network that could be(cid:173)
`gin offering international service after
`1991.
`
`There are two broad categories of for(cid:173)
`eign interest in ROSS. The first consists of
`countries that would use the U.S. GEO(cid:173)
`STAR system until their own capability
`could be fielded. Examples of such for(cid:173)
`eign users are Canada, Mexico, and the
`Caribbean Broadcast Union (a consor(cid:173)
`tium of island states in the Caribbean).
`The second category consists of nations
`who wish to field their own national sys(cid:173)
`tems or join in a regional venture. They in(cid:173)
`clude Australia, Brazil, China, India, and
`the European LOCSTAR consortium
`headed by France; they are all nations
`whose satellite organizations are working
`closely with Geostar on a formal basis.
`
`Interest in ROSS has been expressed
`by other countries as well. Some have de(cid:173)
`ferred due to budgetary considerations,
`lost opportunities, or technical incompati(cid:173)
`bilities. Indonesia and the ARABSAT or(cid:173)
`ganization are included in this category. A
`number of nations are waiting to judge the
`effectiveness .of the system.
`
`Geostar and Embratel, the Brazilian
`national telecommunications company,
`recently signed a memorandum of under(cid:173)
`standing to cooperate in implementing
`ROSS in Latin America. The scope of Bra(cid:173)
`zil's role in the region remains to be deter(cid:173)
`mined. Preliminary studies show the
`dedicated satellite spacecraft, with multi(cid:173)
`ple beams, could provide adequate cover(cid:173)
`age. As a result, Brazil may not elect to
`provide service for the entire region.
`Technical details of Brazil's satellite sys(cid:173)
`tem compatibility remain undetermined.
`
`Geostar recently signed an agree(cid:173)
`ment with Telefonica, the Spanish tele(cid:173)
`phone and telegraph system, that now
`operates the Argentine telephone system
`and is deeply involved with other Latin
`countries. Under the agreement, Geostar
`and Telefonica will jointly develop an
`
`___ ___ ---:.---RDSS,_35
`
`Page 000041
`
`

`
`LOCSTAR Service in the 1990s
`
`ROSS structure for extending coverage to
`this region.
`
`scientific
`national
`The French
`agency, CNES, has formed a European
`consortium, called LOCST AR, to estab(cid:173)
`lish a regional ROSS system that would
`launch its first satellite relay and initiate
`service in 1991. The system would be
`owned by key European governmental
`and private organizations. LOCSTAR was
`formally incorporated in October 1988
`with
`twenty-seven shareholders from
`eight different countries.
`
`The EUTELSAT (European Telecom(cid:173)
`munications Satellite) and the ITELSAT
`(Italian Telecommunications Satellite) are
`
`seen as primary candidate platforms for
`the initial European ROSS. The system
`will provide mobile location and message
`transmission service covering Europe
`first, followed by coverage of Africa and
`the Middle East.
`
`The Indian Space Research Organi(cid:173)
`zation (ISRO) signed an Memorandum of
`Understanding with Geostar in August
`1986 to study the feasibility of implement(cid:173)
`ing ROSS in the Indian Ocean region. The
`ISRO anticipates incorporating one-way
`and two-way ROSS packages in its sec(cid:173)
`ond generation communications satel(cid:173)
`lites, INSAT (Indian Satellite System) 2
`series. The INSAT payloads are set for
`launch in the 1992-93 time frame.
`
`The AUSSAT (Australian National
`Satellite System) has also signed an
`Memorandum of Understanding with
`Geostar, and issued a proposal for ROSS
`spacecraft relays aboard the next genera(cid:173)
`tion of AUSSAT 2 series of three satellites
`scheduled for launch in 1991/1992 and
`1995. The latter satellite may provide
`two-way ROSS messaging service. A de(cid:173)
`cision to acquire one-way service was
`made in 1988; two-way service will be de(cid:173)
`cided in 1991. If approved, the ROSS sys(cid:173)
`tem will be operated by AUSSAT at its
`Belrose earth station in Sydney. The pro(cid:173)
`posed area of coverage may be confined
`to the continent because a larger footprint
`including New Zealand, for example,
`would impose power constraints and re(cid:173)
`strict the usefulness of small terminals.
`
`Geostar Pacific, recently formed, will
`work toward implementing a Pacific Basin
`ROSS system that is compatible with
`GEOST AR and LOCST AR.
`
`The Chinese Academy of Space
`Technology (CAST) is undertaking stud(cid:173)
`ies on incorporation of ROSS in their next
`generation of satellites planned for the
`
`_3 6 -RDSS-------
`
`Page 000042
`
`

`
`early to mid-1990s. A technical feasibility
`study has been completed. Severalop(cid:173)
`tions are under consideration: an applica(cid:173)
`tion of GPS service,
`fielding an
`independent ROSS system, and provid(cid:173)
`ing coverage that includes Southeast
`Asia.
`
`Japan has also expressed interest in
`using an ROSS system. Both telecom-
`
`munications arms of the Japanese Gov(cid:173)
`ernment (the Ministry of Post Telecom(cid:173)
`munications and Nippon Telephone and
`Telegraph) are said to favor a mobile
`voice capability, but it may be imple(cid:173)
`mented in conjunction with ROSS. A
`space communications committee is ex(cid:173)
`amining an ROSS model for possible ap(cid:173)
`plication in Japan.
`
`______ _ RDSS_
`
`37
`
`Page 000043
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`

`
`Page 000044
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`

`
`The Nerve Center
`
`Central
`Control
`
`WHA T CAPABILITIES DOES CENTRAL PROVIDE?
`
`ROSS Central is the nucleus for all
`functions of the network. A combination
`satellite earth station, network master
`control, and message distribution facility,
`the Central Control Facility is the conduit
`between all users and recipients of ROSS
`services.
`
`The earth station portion of a Central,
`which is referred to as the "hub," consists
`of appropriate satellite communications
`antennas and redundant radio frequency
`equipmentforsignal acquisition and proc(cid:173)
`essing. Currently, GEOSTAR Central is
`located in downtown Washington, ~C. It
`
`is configured with twin Ku-Band five(cid:173)
`meter dishes mounted on the roof of the
`Geostar corporate headquarters building.
`
`In the early 1990s, when larger C(cid:173)
`Band antennas are required to support
`GEOSTAR dedicated satellites, the com(cid:173)
`munications antennas and supporting
`equipment will be moved to new sites.
`Geostar has already established a hub at
`Woodbine, Maryland, for control of Sys(cid:173)
`tem 2C and is investigating the placement
`of an alternate Central in Colorado for
`System 3.
`
`DSS
`
`Page 000045
`
`

`
`maintains user identification data bases
`and traffic routing instructions. The Cen(cid:173)
`tral, continuously staffed by two to four
`personnel, interacts directly with end us(cid:173)
`ers, providing a host of ROSS services.
`Individual users may deal personally with
`the Central, or a large consumer segment
`(such as the trucking industry) may have
`its traffic bulk-shipped to a broker for spe(cid:173)
`cialized processing and subsequent inter(cid:173)
`nal distribution.
`
`OPERATION
`OF CENTRAL
`
`The RDSS Central transmits a gen(cid:173)
`eral interrogation signal, addressed to all
`user terminals, through one ofthe satellite
`relays many times per second. The out(cid:173)
`bound signal provides system wide time(cid:173)
`synchronization for the network. Out(cid:173)
`bound traffic may include network control
`instructions to terminals (transparent to
`the user) or messages and position calcu(cid:173)
`lation results to end users.
`
`Inbound signals (messages) from us(cid:173)
`er terminals provide ranging data crucial
`for locating positions. The signals are de(cid:173)
`tected, verified, and identified as to indi(cid:173)
`vidual user terminal through the use of
`unique identification codes. As required,
`the Central can compute the user's posi(cid:173)
`tion, and process and route message traf(cid:173)
`fic to an electronic mail box, to the user's
`home office, or other destinations as
`specified.
`
`The Central maintains a master sys(cid:173)
`tem clock for network reference. It also
`maintains automated files and storage fa(cid:173)
`cilities for all user identifications, and for
`cross-correlation with physical identifica(cid:173)
`tions and traffic routing instructions.
`
`Currently processing
`more than one and
`a half million
`messages per month
`
`Geostar's control segment consists of
`Communications Satellite Corporation
`(COM SAT) spread spectrum modulation
`and demodulation equipment and net(cid:173)
`work operations software under the con(cid:173)
`trol of a Hewlett-Packard computer
`system using a UNIX-based operating
`system. The control hub at the Central en(cid:173)
`codes and decodes spread spectrum sig(cid:173)
`nals, calculates position fixes, and routes
`traffic externally to the network as well as
`internally for electronic sorting and distri(cid:173)
`bution. Today, at GEOSTAR Central, a
`network of Hewlett Packard 9000 series
`computers capable of supporting approxi(cid:173)
`mately 50,000 subscribers is on line. The
`system is modular to allow for growth as
`network traffic increases. The computers
`are connected in a local area network,
`where packet routers direct message traf(cid:173)
`fic to electronic mailboxes and real-time
`links to customers.
`
`The Central's message distribution
`function sends and stores messages, and
`
`_40 - RDSS- - - - - - -
`
`Page 000046
`
`

`
`In maintaining network operation, ap(cid:173)
`proximately a dozen spreading codes
`may be employed by ROSS Central to
`help differentiate among
`the various
`classes and densities of users. For exam(cid:173)
`ple, one code may be allocated for trucks,
`another for aircraft, and perhaps a third for
`emergency vehicles. Should saturation,
`conflict, or contingency arise, the Central
`can shift users to other spreading codes.
`The flexibility to move a user or a class of
`users at will among a number of codes is
`essential for efficient operation.
`
`Electronic Mailbox Service
`
`When processing traffic, the ROSS
`Central identifies the user, screens por(cid:173)
`tions of messages for special routing in(cid:173)
`structions, and distributes traffic to a user
`addressee, a home office, or mailbox. The
`Central can store and forward message
`traffic intended for a user who may be
`temporarily unavailable. The Central may
`forward all unanswered traffic to a mail(cid:173)
`box and, upon detecting the next trans(cid:173)
`mission of a given user terminal, relay any
`
`...
`
`I I I
`
`111""1
`
`.;
`
`Geostar Central Accesses, Stores and Routes Message Traffic
`
`_______ RDSS_41
`
`Page 000047
`
`

`
`ways. The three most common methods
`are:
`
`• Conventional dial-up telephone
`
`•
`
`Leased line (using X.25 message
`packet protocol)
`
`• Small-scale earth station (VSAT)
`
`Customers may access mailboxes
`themselves, or they may arrange for
`ROSS Central to notify them when traffic
`is available. This interaction can occur as
`often as every 10-15 seconds; however,
`hourly or daily retrieval may be the norm.
`Additionally, users can
`redirect or
`preempt the normal process by attaching
`a special code to a message that will
`specify one of the four traffic priorities or
`precedences. For example, an emer(cid:173)
`gency precedence will prompt Central to
`initiate immediate connection with the us(cid:173)
`er's home office, or other persons or
`agencies, as appropriate. For emergency
`traffic, a standard procedure adopted
`by the Central requires the initiation of
`both an electrical contact and a voice
`acknowledgement with the customer's
`home office.
`
`Growing Capability of the Central
`
`Beginning with System 3 service, the
`Central will be capable of geolocating
`every transmission; however, thiscalcula(cid:173)
`tion generally will not be performed rou(cid:173)
`tinely unless the customer requests the
`service.
`
`The ROSS Central is expected to of(cid:173)
`fer a variety of "value added services" to
`meet users' special needs. For example,
`as the user population expands, the Cen(cid:173)
`tral will be able to "observe" local vehicle
`traffic patterns across the nation based on
`timely analysis of position reports from
`
`GEOSTAR Customer Service Representative
`
`stored traffic at that time. Normally, traffic
`will be retained for up to three months.
`The user may arrange for messages to be
`retained for a longer period.
`
`Recognizing the need to maintain the
`confidentiality of user traffic and position(cid:173)
`ing data, the ROSS system is designed to
`protect customer privacy. A user will
`never have his position reported or a mes(cid:173)
`sage sent to another without his permis(cid:173)
`sion. Because network functioning is fully
`automated, most user transactions are
`transparent to Central operating person(cid:173)
`nel, although specific files and mailboxes
`can be accessed by the Central's staff on
`demand. In fact, as a service to the truck(cid:173)
`ing industry, GEOSTAR Central main(cid:173)
`tains a display of vehicle movements and
`can recall historical files that depict indi(cid:173)
`vidual truck routes.
`
`A customer home office can access
`its mailbox at Central in one of several
`
`_4 2 - RDSS- - - - - - - - - -
`
`Page 000048
`
`

`
`like users such as automobiles, commer(cid:173)
`cial trucks, or emergency vehicles. The
`Central also could provide users with re(cid:173)
`routing or other instructions, thus allowing
`them to avoid congested areas.
`
`Billing
`
`The Central maintains a record of all
`message
`transac