Chapter Contents

 

8.0 Satellite Systems

 

8.1 Satellite Applications

8.1.1 Satellite Market

8.1.2 DBS

8.1.3 VSAT

8.1.3.1 A&P VSAT Network

 

8.2 Satellite Orbits

8.2.1 GEO Satellites

8.2.2 Molniya Orbit

8.2.3 MEO Satellites

8.2.4 LEO Satellites

8.2.5 High Altitude Long Endurance Platforms

 

8.3 PCSS

Some Satellite System Facts

8.3.1 AceS

8.3.2 AMSC (Skycell)

8.3.3 Aries

8.3.4 Astrolink

8.3.5 Celestri

8.3.6 Cyberstar

8.3.7 EAST

8.3.8 ECCO

8.3.9 Ellipso

8.3.10 E-Sat

8.3.11 FAISAT

8.3.12 Gemnet

8.3.13 GE*Star

8.3.14 GE Starsys

8.2.15 Globalstar

8.2.16 ICO

8.3.17 Inmarsat-3

8.3.18 Intelsat

8.2.19 Iridium

8.3.20 LEASAT

8.3.21 Leo One

8.3.22 Movisat

8.3.23 M-Star

8.3.24 Odyssey

8.3.25 ORBCOMM

3.3.26 PanAmSat

8.3.27 Satphone

8.3.28 SkyBridge

8.3.29 Spaceway

8.3.30 Teledesic

8.3.31 VITAsat

 

8.4 Canadian Communications Satellites

8.4.1 Anik-B

8.4.2 MSAT

 

8.5 GPS

 

8.6 Satellite Microwave Channels

8.6.1 Access Methods

8.6.2 Satellite Frequency Bands

 

8.7 Satellite Details

8.7.1 Satellite Construction

8.7.2 Galaxy Satellites

 

8.8 Satellite Launch Vehicles

 

Assignment Questions

 

For Further Research

 

 

 

 

 


8.0 Satellite Systems

 

Objectives

This section will:

Examine direct broadcast satellites

Discuss PCSS

Introduce GPS

 

The world wide space industry employs abut 1.2 million people. In 1998 it generated 98B$US. This is expected to grow to 137.8B$US by 2002.[1]

The deployment of satellites has not yet become routine. It is always fraught with danger.

 Galaxy 10.

There are a phenomenal number of satellites and debris in orbit. For more information about debris, refer to:

 For Advanced Students

http://nmsp.gsfc.nasa.gov/tdrss/tdrsshome.html

http://sn-callisto.jsc.nasa.gov/newsletter/news_index.html.

http://www.eurobird.org/

 

EUTELSAT (European Telecommunications Satellite Organization), is the leading satellite operator in Europe, managing 18 geostationary telecommunications satellites. http://www.eutelsat.com/

Minimum Reading

http://www.space.com/spacenews/

 

8.1   Satellite Applications

Satellites support a number of applications including:

Communications systems

Broadcasting systems

Remote sensing

Global positioning and navigation

Search and rescue

Weather and pollution monitoring

Surveillance

Approximate Number of Satellites[2]

Country

Satellites

Canada

16

China

15

France

24

Germany

15

India

11

Japan

55

United Kingdom

18

United States

658

Europe

27

International

51

Other

10

 

 For Advanced Students

Satellite Communications by Hart

Satellites in Geostationary Orbit by Johnson

http://www.lyngsat.com/index.html

http://www.sbca.com/

http://www.esatcom.net/

http://www.msua.org/mobile.htm

http://www.estec.esa.nl/mercure/homepage.htm

http://www.satellitetoday.com/

http://www.ses-americom.com/

http://www.astronautix.com/

http://www.isr.umd.edu/CSHCN/

http://www.cs.ucl.ac.uk/staff/S.Bhatti/D51-notes/node24.html

 

8.1.1  DBS

Europe is the largest DBS market in the world. In 1999 there were more than 250 TV channels being broadcast in 24 languages.

The first TV satellites operated in the C-band, and broadcast between 5 to 24 watts. C-band receivers require large parabolic antennas.

New direct broadcast satellites transmit television signals use the Ku band and broadcast signal levels up to 200 watts. This reduces the receive antenna size to approximately one meter in. A disadvantage of the Ku band is its high atmospheric losses due to rain.

Ku band satellites often carry 32 x 24 MHz channels. Left and right hand circular polarization is used to allow frequency reuse.

8.1.2  VSAT

Minimum Reading

http://www.spacenet.com/tools/satellite_basics/

 

VSAT networks carry voice, data, and video services via a small dish satellite link. Two principle applications for this type of service are ALOHA packet networks, and cellular radio facilities.

US VSAT Market Share[3]

HNS

59%

AT&T Tridom

14%

GTE Spacenet

13%

Scientific Atlantic

9%

Others

4%

 

Current domestic satellites have a few broad beams, however this makes for a very limited user environment. Multiple narrow or spot beams are required to cope with the growing number of customers. Frequencies can be reused in each of the spots, thus increasing capacity.

VSAT networks are deployed in a star configuration with all traffic being switched through a master control center which does both inter and intra-beam switching. An inter beam communications link therefor requires two hops. Newer designs support switching at the satellite.

A&P VSAT Network[4]

A&P was the first national supermarket chain to replace its dial-up data network with VSAT terminals. Currently, there are about 750 stores in the network. At present, there are more than 20 different food chains operating 5000 terminals.

The A&P central hub uses a 6-meter dish and is located at Columbia Maryland. Remote terminals use 1.8-meter dishes, and communicate via X.25 packets on 56 Kbps channels. Each terminal can interface with PC workstations, cash registers, credit card readers, and bar code scanners.

Food chains use these systems for:

Electronic funds transfer: debit card transactions, credit card verification

Inventory and accounting from the POS terminals

Pricing updates

Audio and video in store advertising

In store sales training

A database on shopper activity allows the company to offer such programs as frequent shopper incentives, electronic coupons and direct-mail promotions.

United States Postal Service

The USPS is the largest retailer in the U.S. with 27,000 small and 7,000 large offices.

The VSAT network is used for point-of-sale data polling, credit authorization, delivery confirmation, software distribution, streaming video, interactive distance learning, and multicast content delivery.

8.2   Satellite Orbits

Minimum Reading

http://satellite.about.com/msub104.htm

 

Satellite networks are often categorized by their orbits:

System

Altitude [Km]

Comments

GEOS

35,786

Geostationary satellites

MEOS

10,000

Medium earth orbit

LEOS

1,000

Low earth orbit

HEOS

 

Highly elliptical orbit

 

 

Ground stations communicate with satellites orbit over a high-powered, microwave link. The area that can receive the satellite downlink is called a footprint.

8.2.1  GEO Satellites

The majority of communications satellites today are in GEO orbit. This orbital plane is located at an altitude of 36,000 Km above the equator. The signal return trip takes about 0.25 seconds.

International regulatory bodies such as the ITU and national government organizations like the FCC assign communications satellite positions. The geostationary spacing is typically 2o however, increasing demands may lower this to 1o.

A satellite that orbits around the earth at the same rate that the earth turns is known as a synchronous orbit. Synchronous orbits can be of any inclination. If they are polar orbiting, the satellite will appear to be over the same spot at the same time every day.

Remote sensing satellites can be place in orbits that are synchronous with the earth’s rotation over a longer period than a day, and thus will be able to view the entire ground surface over a number of orbits.

If a geosynchronous orbit is placed over the equator, the satellite will appear to stop moving in the sky. This is referred to as a geostationary orbit.

The gravitational acceleration of an object as a function of altitude is:

The centrifugal acceleration on a satellite is given by:

For a stable orbit, the two forces associated with these accelerations must be equal:

Solving for rs we obtain:

Therefore the height above the earth is 42,254 Km - 6378 Km = 35,876 Km or 22,292 miles.

The velocity of a satellite in a circular orbit is given by:

This works out to 3.073 Km/Sec for a satellite in a geostationary orbit.

These satellites will appear directly overhead at the equator. As one moves northward, the orbital plane appears to move south. Since a satellite must appear about 5o above the horizon in order to be seen by a ground station, it is not possible to receive signals within about 1000 km of the poles. Consequently, countries with significant population at extreme northern (or southern) latitudes must rely upon a different obit for communications satellites.

8.2.2  Molniya Orbit

The former USSR is not able to make great use of geostationary satellites, because of the northern latitude of the country. Consequently, communications satellites have required a slightly different approach.

Orbital inclination

63.4o

Orbital period

719.19 minutes

Perigee

1000 Km

Apogee

39,375 Km

 

The size of the ellipse was chosen to make the orbital period equal to half a sidereal day, and therefore in synchronism with the earth. Because the earth is an oblate spheroid, most elliptical orbits of this type would slowly precess around the earth. However, this apsidal rotation does not take place for an orbit with an inclination of 63.4o.

The satellite remains visible for 11 of its 12-hour orbit. Several satellites are required to provide continuous coverage. The earth stations are quite complex since they must track the satellite.

8.2.3  MEO Satellites

MEO satellite orbit at an altitude of about 8000 miles. Communications signals travel a shorter distance and have less signal loss, thus allowing the use of smaller, lightweight-receiving terminals. The return trip time for a MEO satellite is less than 0.1 seconds. These satellites are often in inclined orbits.

8.2.4  LEO Satellites

Several LEO systems have been proposed at an altitude of about 500- 1000 miles. The return trip time for these systems is about 0.05 seconds. These satellites are often placed in polar orbits.

Some of the frequency bands for these systems are: 800 MHz, 2 GHz, and 20-30 GHz range.

8.2.5  High Altitude Long Endurance Platforms

HALE platforms are airplanes carrying a communications repeater at an altitude of about 70,000 feet. They can be powered by high efficiency turbine engines or a combination of battery and solar power. Transmission delays are less than 1 mSec.

8.3   PCSS

WARC -92 allocated part of the L-band [1.5 to 1.7 GHz] for universal personal communications. This includes both terrestrial and satellite components.[5]

PCSS depends upon the deployment of cheap and reliable LEO satellites. Although a considerable amount of money has been spent on developing and promoting these systems, here is still considerable debate as to whether these systems are cost effective.[6]

Some of the technologies, needed to support these systems include[7]:

Small communications satellites

Phased array antennas

Radiation tolerant semiconductors

Advanced baseband processing architectures

Distributed network architectures

There are a number of proposals for worldwide satellite communications. Initially it was thought that these systems might compete with local telcos and cellular radio systems. It is now thought that one of the main users of the system might be the telcos themselves. This is because without telco cooperation, the satellite service customer base might never come into existence. The Globestar system is to be sold exclusively to telcos to supplement the existing cellular system, and will be transparent to the end-users.

It may be that these systems will be useful in providing connection to existing PSTN facilities where cellular service is not available. If this is the case, the largest customers will be in developing countries.

Since these systems operate on a global scale, some rather important global issues must be addressed. Some of these include:

Frequency allocations

Signaling protocols

Connection to PTTs

Regulatory issues

Licensing and tariffs

Some analysts give PCSS approximately 10% chance for success as envisioned.[8]

Some Satellite System Facts (subject to change)

System

# Sat

Comments

ACeS

2

Asia Cellular Satellite, GEO, Voice, data, paging, e-mail

Aries

48

Australian Resource Information and Environment Satellite

Astra

13

Provides European TV, internet & multimedia communications. Part of SES Global

Celsat

3

GEO, Voice, data, fax, paging

ECCO

12

LEO, South America, Voice, data, fax, paging

Ellipso

14+3

LEO/MEO, Voice, data, paging, e-mail, CDMA

E-Sat

6

Data Services

FAISAT

26

Data, paging, voice

GEMnet

38

Data

GE Starsys

24

Data messaging

Globalstar

48

B-LEO, Voice, data, fax, paging, GPS, CDMA

ICO

10+2

MEO, Voice, data, fax, paging, TDMA

Iridium

66

B-LEO, Voice, data, fax, paging

Inmarsat P

10 + 2

 

Koskon

32

B-LEO, Voice, data, fax, paging

LEO One

48

Data

M-Star

72

Broadband services

Odyssey

12

B-LEO, CDMA

Orbcomm

48

Data service

SkyBridge

80

Broadband LEO

Spaceway

12

GEO, Voice, data, video, broadband

Teledesic

840

LEO, Broadband services, ATDMA+, CDMA

Thuyara

2

GEO, Voice, data, paging, e-mail

VITAsat

2

Data services for volunteer disaster relief.

 

 For Advanced Students

8.3.1  AceS

http://web.acesy.com/menu.htm

Coverage Map

 

ACeS (Asia Cellular Satellite System) is a combined cellular and satellite wireless system from Ericsson that provides GSM services in the Asia Pacific Region. It was expected to be available in 1999 to serve a combined population of three billion. ACeS has signed over 19 roaming agreements with GSM operators.

The system uses a Garuda geo-stationary satellite. A second satellite will expand the ACeS footprint into the West and Central Asia, Europe, and Northern Africa.

The satellite will have two 12-meter antennas that will create 140 spot beams and support 11,000 simultaneous telephone channels.

8.3.2  AMSC (Skycell)

www.skycell.com appears inactive.

Status

Unknown

Cost

 

Orbit

There are two HS601 GEO satellites. The MSAT satellite can act as a backup.

Uplink

Transmit frequency: 1.6265 to 1.6605 GHz

Downlink

Receive frequency: 1.525 to 1.559 GHz

Data rate

Data rate up to 4800 bit/s

Owners

Hughes Communications Corp., RonaldBaron, Singapore Telecom, AT&T.

Services

Mobile and fixed voice, messaging, GPS

Coverage

USA, Mexico and the Caribbean.

Market

AMSC is targeting businesses that require remote communications to thrive. AMSC-2 may provide handheld mobile services. Airtime rate ranges from US$0.85 to US$1.99 per minute, depending on applications.

 

8.3.3  Aries

The ATM Research and Industrial Enterprise Study (ARIES) is an experiment in high-speed terrestrial and satellite communications in the petroleum industry and for other applications. Using the NASA ACTS satellite, and technologies from various project partners, the ARIES Project has demonstrated world-class achievements in fixed and mobile telecommunications, in support of real-world industry goals and objectives.

Astra

http://www.astra.lu/ or http://www.ses-astra.com/

This 16-satellite system is built by GE Astro Space and provides radio and TV broadcasting, high speed internet, webcasting, Business TV, and interactive shopping channels, in Europe.

They have 16 transponders with an EIRP of 52 dBw and a bandwidth f 26 MHz. They operate in the 11.2 – 11.45 GHz region.

8.3.4  Astrolink

www.astrolink.com

This system consists of:

Four Regional Network Control Centers (RNCCs) - assign network resources, validate users, and monitor thesystem.

One Master Network Control Center (MNCC) - overall network resource management and collect usage statistics.

Two Satellite Operation Control Centers (SOCCs) - perform satellite housekeeping functions.

Three Telemetry, Tracking and Control (TT&C) facilities - enable the SOCCs to communicate with the system.

30 to 50 Gateway Earth Stations - allow customers to connect at data rates up to 110 Mbps. The gateways provide protocol conversions for T1/E1, TCP/IP, frame relay and X.25, and other protocols.

 

Status

Expected to be in operational service in 2000

Cost

US$4 billion.

Orbit

Nine A2100 GEO satellites in five orbital slots

Uplink

28.35 - 28.6 and  29.25 - 30 GHz

Downlink

19.7 - 20.2 GHz

Data rate

16 Kbps to 9.6 Mbps, total capacity of 6.5 Gbps per satellite

Owners

Lockheed Martin Telecommunications

Services

Principally data (over ATM)

Coverage

Worldwide

Market

Lockheed plans to market Astrolink to business and common carriers to provider worldwide high-speed, two-way data services.

 

8.3.5  Celestri

This system has now become part of Teledesic.

Status

This system has now become part of Teledesic

Cost

US$12.9 billion. (This includes the manufacture and launch cost of the first satellite of the Millennium project).

Orbit

63 LEO satellites in 7 planes are orbiting at an altitude of 1400km for the Celestri LEO constellation. Expected lifetime of eight years

Uplink

28.6-29.1 & 29.5-30.0 GHz

Downlink

18.8-19.3 & 19.7-20.2 GHz

Data rate

Sharing with Teledesic on a secondary basis. Data rates of up to 155.52 Mbps The Celestri LEO will be combined with up to four GEO satellites, possibly providing inter-satellite links, as well as complementary services.

Owners

Motorola Inc.

Services

Broadband data services, including interactive multimedia and point-to-point real-time user communications. It will also be suitable for fixed voice services.

Coverage

Up to 70 degrees north and south latitude

Market

Broadband Internet and intranet services from fixed terminals, particularly to large business users. Motorola intends to offer wholesale space segment capacity to carriers and service providers (not end-users). The Millennium and M-Star projects will be incorporated into Celestri.

 

8.3.6  Cyberstar

http://www.cyberstar.com/

Status

A dedicated constellation, which is intended to be ready in 1999, with full operational service expected in 2000.

Cost

US$1.6 billion.

Orbit

Three GEO satellites operating in Ka band.

Uplink

 

Downlink

 

Data rate

 

Owners

Loral Space & Communications, Alcatel Espace

Services

Internet access, broadband interconnection, VOD and other data services.

Coverage

North America, Asia and Europe

Market

Broadband Internet and intranet access from low-cost fixed terminals. Loral has formed a strategic alliance with Alcatel to market the Cyberstar and Skybridge projects together.

 

8.3.7  EAST

Euro African Satellite Telecommunications

Status

EAST is expected to be in service around 2002

Cost

US$700 million (not including cost of gateways)

Orbit

A Eurostar 3000 GEO satellite

Uplink

 

Downlink

 

Data rate

 

Owners

Matra Marconi Space

Services

Handheld mobile and rural/fixed telephony service. Main focus is on voice, but it will also offer data services.

Coverage

Africa and Middle East plus parts of Europe

Market

Provides low cost services that complement terrestrial fixed and mobile services.

 

8.3.8  ECCO

http://www.cciglobal.com/new2/index.html

The system will offer mobile services between 23o north and south latitude. The system will consist of a single plane of 12 satellites in circular orbit around the equator, at an altitude of 2,000 km.

The downlink is 2483.5 - 2500 MHz and the uplink is 1610 - 1626.5 MHz. Each satellite will have 24 beams and can support up to 192,000 subscribers.

8.3.9  Ellipso

http://www.ellipso.com/

Status

Ellipso has recently been granted a US license and is expected to start operational service by 2000.

Cost

US$910 million.

Orbit

14 (with 3 in orbit spares), including elliptical LEO satellites orbiting at 520km and 7846km, and circular LEO satellites orbiting at 8040km.

Modulation

CDMA mobile users 5 MHz, fixed users 2.5 MHz

Uplink

1610.0 – 1621.5 MHz

Downlink

2483.5 – 2500.0 MHz

Data rate

Data rates of up to 9600bit/s.

Owners

Mobile Communications Holdings, Vulva Communications, Spectrum Networks Systems, Orbital Sciences Corp., Harris Corp., IAI, Spectrum Astro Inc., L-3 Com, Lockheed Martin.

Services

Mobile and fixed voice, data, fax, paging, GPS.

Coverage

Primarily the northern hemisphere but also as far south as 55 degrees latitude in the southern hemisphere.

Market

An extension of terrestrial mobile and fixed services to remote areas.

 

8.3.10 Emsat

Coverage Map

 

Emsat is a part of the Eutelsat system. It provides voice, fax data communications, position reporting and monitoring services. It is used by trucking fleets and ships in the European theatre.

8.3.10 E-Sat

http://www.esatinc.com/

Status

The FCC has yet to grant E-Sat the operational license

Cost

US$50 million

Orbit

Six LEO satellites orbiting at 1260km.

Uplink

 

Downlink

 

Data rate

 

Owners

Echostar Communications, DBSIndustries

Services

Store and forward messaging

Coverage

Focused mainly on North America

Market

Provide remote equipment monitoring for North America gas and electricity utility companies.

 

8.3.11 FAISAT

http://www.finalanalysis.com/

Status

Full operation is expected no later than 2002.

Cost

US$250 million.

Orbit

36 LEO satellites in 6 orbit planes inclined at 610 plus 2 satellites inclined at 810.

Uplink

 

Downlink

 

Data rate

300 bps to 300 Kbps

Owners

Final Analysis, Polyot Enterprises

Services

Two-way messaging, asset tracking, monitoring and control, file transfer. Services are offered in real-time, near real-time, and store & forward modes.

Coverage

Worldwide

Market

Multiple market applications in the US and international markets.

 

8.3.12 Gemnet

http://www.cta.com/

Status

Service was expected to begin in 1999.

Cost

US$160 million

Orbit

38 LEO satellites in 1000km circular orbits. Expected lifetime is 5 - 7 years

Uplink

 

Downlink

 

Data rate

 

Owners

CTA Inc. Orbital Sciences announced in July 1997 that it would be buying CTA’s space system unit.

Services

Tracking & monitoring, email, paging.

Coverage

Global coverage

Market

Monitoring and tracking markets with low data requirements.

 

8.3.13 GE*Star

http://www.geamericom.com/satellite/index.html

Europe*Star Brochure

 

Status

 

Cost

$4 billion

Orbit

9 GEO satellites  from Alcatel

Uplink

28.35 - 28.6 and 29.25 - 30 GHz

Downlink

 

Data rate

384 Kbps to 40 Mps.

Owners

GE Americom

Services

 

Coverage

 

Market

 

 

8.3.14 GE Starsys

http://www.geamericom.com/satellite/index.html

 

Status

Launches were expected to begin in July 1998 and service was expected to be operational in 1999. However, GE has returned its operator’s license to the FCC as of Aug 4 1997.

Cost

US$170 million.

Orbit

24 satellites in 4 planes orbiting at 1067km.

Uplink

 

Downlink

 

Data rate

 

Owners

GE American Communications, CLS North America.

Services

Messaging, asset tracking, paging.

Coverage

Worldwide, but North America and Europe would have been key areas for real-time services.

Market

GE Starsys would have provided near-real-time services as well as store-and-forward services in remote areas.

 

8.2.15 Globalstar

Minimum Reading

http://www.globalstar.com/

GlobalStar Brochure

Globalstar constellation.

Globalstar Coverage Map

 

Status

The first launch is expected in October 1997, with initial commercial operations starting in 1998. Full operational coverage is expected by 1999.

Cost

US$2.6 billion for satellites with US$2.35 billion already financed.

Orbit

48 LEO satellites in a circular orbit, comprising 8 planes, at an altitude of 1400km. Expected satellite lifetime: 7 .5 years

Uplink

User uplink frequency: 2.4835 - 2.5 GHz

Feeder uplink frequency: 5.025-5.225 GHz

Downlink

User downlink frequency: 1.61-1.6265 GHz

Feeder downlink frequency: 6.875-7.075 GHz

Data rate

Voice: Typically 2400bit/s

Data: 9600 bit/s (maximum)

Owners

Loral, Qualcomm, AirTouch Communications, DACOM/Hyundai, France Telecom/Alcatel, Daimler Benz, Vodafone, Alenia Spazio, Elsag Bailey, Finmeccanica, Space System/Loral.

Services

Primarily mobile and fixed voice services, with paging, messaging, fax and GPS services as secondary applications.

Coverage

Can cover up to 74 latitudes provided that gateways coverage is available. Each gateway is expected to provide mobile coverage for an area almost as large as Western Europe.

Market

Low-cost, high-quality services to under-served areas  particularly in developing countries.

 

The Globalstar system has 48 LEO satellites in eight planes at an altitude of 1414 km. The constellation is designed for 100% single satellite coverage between ±70o latitude, and 100% dual or higher satellite coverage between 25o to 50o north or south latitude.

Globalstar will employ path diversity and three satellites may be used to complete the call. It uses CDMA for the mobile link.

It offers data rates of 1.2, 2.4, 4.8 and 9.6 Kbps. The vocoder rate drops to 1.2 Kbps when no voice activity is detected. This reduces interference and increases capacity, while maintaining synchronization and conveying background comfort noise.

The antennas create elliptical footprints along the satellite trajectory to increase the dwell time.

The system connects to the PSTN via 100 to 210 earth stations.

The system sells access to local service providers. They in turn only use the system when a terrestrial connection cannot be established.

8.2.16 ICO

Minimum Reading

http://www.ico.com/

http://www.i-co.co.uk/

 

Status

First launch is scheduled in 1998. Full operation is scheduled for the year 2000.

Cost

cost is expected to be $2.6 billion. To date, ICO has currently raised $1.5 billion

Orbit

10 operational medium earth orbiting (MEO) satellites (HS 601) circling at an altitude of 10 355km. Lifetime is expected to be 12 years.

Uplink

User uplink frequency: 1.98-2.02 GHz

Feeder uplink frequency: 5 GHz

Downlink

User downlink frequency: 2.065-2.1 GHz

Feeder downlink: 7 GHz

Data rate

Voice: 4800 bit/s

Data: 38400 bits/s planned

Owners

45 telecommunications companies, Inmarsat, Hughes Electronic Corp.

Services

Mobile voice, data, fax, messaging.

Coverage

Global coverage.

Market

Domestic and international travelers, business and government organizations, commercial vehicles, maritime and aeronautical vessels, and residents of rural and remote areas.

 

 Satellites in Orbit               Spot beams

ICO Global Communications Inc. was established in January 1995.

The major owners are NEC Corp, Hughes Network Systems and Ericsson. NEC will provide the access nodes, the network management systems and systems integration. Hughes will provide the satellite and Ericsson the mobile switching centers. The Satellite Control Centre near London will manage the system.

The network will consist of  12 satellites in 2 inclined orbits at an altitude of 10,355 km. ICO satellites use the HS601 geostationary satellite bus and support 4,500 telephone channels.

Satellite diversity allows two or more satellites to access the same mobile terminal. The satellites relay the customer’s channel to one of 12 earth stations linked to the PSTN.

The system uses dual mode terminals incorporating GSM and the local cellular standard.

A Zenit rocket carrying the first ICO Global Communications satellite exploded shortly after taking off from the Sea Launch platform in the South Pacific Sunday. (Mar 2000)

The satellite, built by Hughes Space and Communications, was the third launch for the Boeing-led venture. Sea Launch successfully launched a dummy satellite a year ago and a DirecTV satellite in October.

The lost satellite was valued at $100 million. Not only does the loss represent another setback for to ICO, which filed for bankruptcy protection last year, it's another blow to the struggling mobile satellite services market.

In addition to Boeing, Energia of Russia, Kvaerner Maritime of Norway and KB Yuzhnoye/PO Yuzhmash of the Ukraine are partners in the Sea Launch venture.

8.3.17 Inmarsat-3

Minimum Reading

http://217.204.152.210/index.cfm

 

Status

Four satellites have been launched providing full global coverage, with one backup satellite to be launched near the end of 1997. A fourth generation, the Horizons project, is expected to be launched in 2001.

Cost

Approximately US$690 million.

Orbit

Five GEO satellites using spot beam technology. Satellite lifetime: at least 13 years

Uplink

 

Downlink

 

Data rate

Voice: 2400 bit/s

Data: 2400 bit/s and above

Owners

Inmarsat signatories

Services

Mobile voice, data, fax, positioning

Coverage

The satellites will be over the four oceanic regions, providing coverage up to 70 degrees north and south latitudes. Spot beams are targeted at the main landmasses.

Market

Main new product is Inmarsat mini-M, a notebook-sized telephone which can be used virtually anywhere in the world. This is targeted mainly at high-end users with a need to communicate in remote areas.

 

8.3.18 Intelsat

Minimum Reading

www.intelsat.com

http://www.intelsat.int/

 

Intelsat developed the world’s first international satellite communications system. It began with the Early Bird 1965, and by 1969 global coverage was acheived.

The present system supports voice, video, the internet, corporate and private networks in about 200 countries. It is presently consists of 17 satellites in geostationary orbit.

Intelsat Series

Image

Comments

V

Used both C and Ku bands. Spatial separation and polarization diversity, allowed some frequencies to be reuse four times. 15 of these satellites were built by Ford Aerospace.

VI

These are the largest commercial spacecraft ever built.  Transponders static switch matrices or satellite-switched time division multiple access [SS/TDMA]. C-band frequencies are reused six times. Ku-band frequencies are reused twice. 5 of these satellites were built by Hughes.

VII

There are 4 of these satellites. They can reconfigure the coverage capability in-orbit

VIII

There are four of these satellites. They use six-fold C-band frequency reuse.

IX

Supports broadband applications such as trunking; telemedicine and remote learning; interactive video and multimedia.

 

8.2.19 Iridium

This system went bankrupt, but was restructured as Iridium Satellites.

Minimum Reading

http://www.iridium.com/

Iridium Constellation.

Iridium Product and Services Brochure

Iridium

Status

Partly operational

Cost

$4.4 billion +

Orbit

66 satellites orbiting at 780km (circular), using inter-satellite links. Expected satellite lifetime: 7 – 9 years

Uplink

User frequency: 1.616-1.6265 GHz

Feeder uplink frequency: 2.91-29.3 GHz

Feeder downlink frequency: 19.4-19.6 GHz

Inter-satellite link frequency: 23.18-23.38 GHz

Downlink

 

Data rate

Voice: 2.4 Kbps

Data: 2.4 and 10 Kbps.

Owners

Motorola, Nippon Iridium Corp, Vebacom GmbH, Sprint, BCD Mobile Communications Inc, STET, DDI, UCOM, SK Telecom Corp., PT Bakrie Communications Corp., Raytheon.

Services

Voice, paging, data, fax.

Coverage

Global coverage, including mid-ocean and remote areas.

Market

Business professionals are expected to be the main customers. It is also expected to be an invaluable tool for aeronautical and marine uses.

 

The first proposed LEO system was  Iridium, spearheaded by Motorola. This system initially proposed to use a combination of 77 low earth orbit satellites and the cellular telephone system. This ambitious scheme was eventually scaled down to 66 satellites many of which went into orbit. Unfortunately, the entire system went into bankruptcy early in 2000.

Some market forecasts estimated there would be 1.8M subscribers in the year 2001, growing to 2.8M in 2006, while others suggest it could be 3 times larger. Some have estimated the system cost at 2.5B$US while others place it as high as 3.4B$US[9] or even higher[10].

This  system was intended to supplement ground based cellular systems, and provide government and business customers with advanced communications while traveling in less advanced countries.

Some of the system characteristics were:

7 to 9 year satellite life expectancy

Six polar orbital planes inclined at 86.4o

Eleven active and one spare satellite per orbital plane

Orbital period 100 minute 28 seconds

Orbital elevation of 780 km

Cell diameter: 372 nautical miles

48 spot beams per satellite

Telephone & messaging link: L-band (1.616 – 1.6265 GHz)

Access: FDMA/TDMA

Inter-satellite: link Ka-band (23.18 – 23.38 GHz)

Ground segment: Downlink Ka-band (19.4 – 19.6 GHz) Uplink Ka-band (29.1 – 29.3 GHz)

Ground based digital switches: Siemens GSM-D900

Maximum number of simultaneous customers per cell: 110 [assuming 10.5 MHz total spectrum]

The services offered include:

Terminals: hand held, portable, and vehicle-mounted .

Position finding

Facsimile service

Dial-up data transmission: 2.4 Kbps, Data direct: 10 Kbps

Worldwide paging

The satellites used 3-axis stabilization and a hydrazine propulsion system. The two solar panels had 1-axis articulation.

The Iridium system was based on the GSM architecture.

 

8.3.20 LEASAT

LEASAT, are US military geostationary satellites.

These enormous spin-stabilized satellites are 4.26 meters in diameter, 6.17 meters high with antennas deployed, and weigh about 7000 kg when launched from the space shuttle. The initial on station weight is 1388 kg.

8.3.21 Leo One Worldwide

Minimum Reading

www.leoone.com

LEO One Satellite

 

Status

FCC license expected by the end of 1997 with commercial service beginning in 2000

Cost

US$250 million

Orbit

48 LEO satellites arranged in 8 orbital planes at an altitude of 950km. Satellite lifetime of 5 years, with 7 years of consumables.

Uplink

148-150.05 MHz

Downlink

137-138 MHz and 400.15 – 401 MHz

Data rate

Subscriber Uplink 2.4 to 9.6 Kbps, Downlink 24 Kbps

Gateway: 50 Kbps

Owners

dBX Corp

Services

Vehicle tracking, status monitoring, emergency alerting, messaging, paging, positioning. Fixed and mobile applications can be served.

Coverage

Leo One will provide store and forward coverage of all points between the Arctic and Antarctic Circles and near real-time service to the most populated regions of the Earth.

Market

Leo One will provide low-cost real-time, mobile and fixed service for industrial, business and personal data communications. 

 

A combination of random access and frequency division multiplexing (FDM) is used for subscriber uplinks. Time division multiplexing (TDM) is used for the other links. All links use shaped offset-QPSK (OQPSK – offset quadrature phase shift keying) modulation in combination with forward error control (FEC) coding.

8.3.22 Movisat

Status

Operational. Another satellite (Morelos-3, based on HS 601HP satellite bus) will be launched at the end of 1998 to replace the aging Morelos-2.

Cost

 

Orbit

Three GEO satellites, Solidaridad 1 and 2 & Morelos 2

Uplink

 

Downlink

 

Data rate

 

Owners

Satelites Mexicanos SA.

Services

Mobile services, rural telephony, messaging, GPS.

Coverage

Mexico, southern USA, Caribbean and Latin America.

Market

Target market is high end-users who need communications in remote areas. The phone is approximately briefcase sized.

 

8.3.23 M-Star

Status

Absorbed by the Celestri project.

Cost

US$6.1 billion

Orbit

72 LEO satellites.

Uplink

 

Downlink

 

Data rate

Data rates of up to 51.84 Mbps.

Owners

Motorola Inc.

Services

Backhaul and high-capacity truncking to networks will be served by M-Star, whereas interactive multimedia services will be served by the Celestri LEO constellation.

Coverage

Global coverage

Market

M-Star will be incorporated into the Celestri project. The M-Star project is intended to target multinationals with global broadband communications needs.

 

8.3.24 Odyssey

According to http://www.comlinks.com/sys/odyssey.htm the project has been cancelled.

Minimum Reading

www.trw.com

 

Status

Current Status US license was granted in Jan 1995, and commercial service was expected to be operating by 2001. According to http://www.comlinks.com/sys/odyssey.htm the project has been cancelled.

Cost

3.2B$US

Orbit

12 satellites at altitude 10354 km with 7 ground stations. Satellite lifetime of 15 years.

Uplink

User uplink frequency: 1.61-1621.35 GHz

Feeder uplink frequency: 29.1-29.4 GHz

Downlink

User downlink frequency: 2.4835-2.5 GHz

Feeder downlink frequency: 19.3-19.6 GHz

Data rate

Voice: 2400 bit/s, data: 9600 bit/s.

Owners

TRW Inc, Teleglobe Inc.

Services

Fixed and mobile voice telephony, fax, digital data, short messages.

Coverage

Worldwide

Market

Odyssey will seek primarily to complement and extend terrestrial fixed and mobile services in remote areas.

 

The Odyssey MEO system was to create stationary ground cells by steering the satellite body. CDMA was chosen for the multiple access method.

Usually at least two satellites would be visible from the mobile terminal and the best link is selected at call set-up.

Earth stations connect the system to the PSTN. Each satellite can support 3000 to 9500 voice circuits depending on the ratio of mobile to fixed terminals.

8.3.25 ORBCOMM

Minimum Reading

http://www.orbcomm.com/

 

Status

The first two satellites have been launched and are operational. The full system is expected to be operational by 1998.

Cost

US$350 million (completely financed)

Orbit

28 LEO satellites orbiting at 775km. 8 additional satellites may be added if there is sufficient demand. Satellite lifetime: 4 years

Uplink

148-149.9 MHz

Downlink

137-138 MHz and 400.05-400.15 MHz

Data rate

Data rate : up to 2400 bit/s (typically 300 bit/s)

Owners

Orbital Sciences Corp., Teleglobe Inc, Technology Resources Industries Bhd

Services

Messaging, email, fax, GPS

Coverage

Worldwide

Market

Orbcomm aims to provide high availability, low-cost, two-way, on-the-move communications over the entire globe.

 

Orbcomm provides worldwide two-way data and messaging services. It includes Orbital Science Corp., Teleglobe, and Technology Resources Industries. It will track vehicles, trailers, shipping containers and monitor utility meters, pipelines, storage tanks, and heavy equipment.

Two satellites are in a near-polar orbit and the rest will be placed in three planes (of 8 satellites) inclined at 45o.

These small satellites (50 kg) can be deployed eight at a time by the air launched Pegasus rocket. The upink operates at 148 - 150.05 MHz and the downlink at 137 - 138 MHz.

3.3.26 PanAmSat

Minimum Reading

http://www.panamsat.com/

The PanAmSat system contains 21-satellites and covers the Americas, Europe, Africa, the Middle East and Asia.

 

8.3.27 Satphone

Appears to be on hold according to http://www.comlinks.com/sys/satphon.htm

Status

The first satellite is scheduled for launch at the end of 1998. Expected to be in service in September 1999

Cost

US$1.7 billion

Orbit

Three GEO satellite systems manufactured by Lockheed Martin.

Uplink

 

Downlink

 

Data rate

 

Owners

Lockheed Martin Telecommunications, Advanced Technology Fund Inc., M.O.Al Amoudi Corp

Services

Mobile & fixed voice

Coverage

The Middle East, Northern Africa and the Mediterranean.

Market

Looking to complement and extend terrestrial fixed and mobile services.

 

8.3.28 SkyBridge

Minimum Reading

SkyBridge Brochure

www.skybridge.com

http://www.skybridgesatellite.com/

http://www.alcatel.com/space/

 

Status

SkyBridge is expected to enter service in 2001 with half of its 64 satellites in operation. Full operation is expected in 2002.

Cost

US$4.1 billion.

Orbit

80 LEO satellites using frequency in Ku band (12 -15 GHz). No inter-satellite links are required.

Uplink

 

Downlink

 

Data rate

16 Kbps to 2 Mbps uplink, and 16Kbps to 20 Mbps downlink

Owners

Alcatel Espace, Loral Space & Communications.

Services

Interactive multimedia, high data rates and real time applications

Coverage

Worldwide

Market

It is primarily aimed at providing broadband access in areas with low or moderate density populations. SkyBridge will be marketed together with Cyberstar.

 

The SkyBridge LEO system provides access to high data rate multimedia services.

The constellation consists of 80 Ku band satellites inclined at 53°.

There will be about 200 gateway stations, each with a coverage radius of 350 Km to connect to the PSTN.

The uplink operates at 12.75 - 14.5 GHz, and the downlink at 10.7 - 12.75 GHz. Circular polarization helps to facilitate frequency reuse. Each satellite supports 18 spot beams. These are steered to create fixed ground cells.

8.3.29 Spaceway

Minimum Reading

http://www.spaceway.com/

 

Status

The first regional system is expected to go online as early as 2000

Cost

US$3.2 billion.

Orbit

Nine HS702 GEO satellites lifetime: 15 years

Uplink

27.5 - 30.0 GHz

Downlink

17.7-20.2 GHz

Data rate

16 Kbps up to 6Mbps

Owners

Hughes Communications Inc.

Services

Fixed voice, video, audio, data and multimedia and VSAT applications

Coverage

Most of the major continents will be covered except for parts of Asiatic Russia. The bulk of the inhabited world will be covered.

Market

Spaceway is expected to provide services in areas where the infrastructure is inadequate to meet the needs. The first target markets are likely to include North America.

 

8.3.30 Teledesic

Minimum Reading

http://www.teledesic.com/

 

Status

First launch expected in 2000, with operational service expected to commence in 2002.

Cost

$9 billion.

Orbit

Believed to be 288 (rather than 840) satellites in a circular low earth orbit. Lifetime of satellites: 10 years

Uplink

 

Downlink

 

Data rate

16 Kbps to 2.048 Mbps or higher

Owners

Bill Gates, Craig McCaw, Boeing Co

Services

Will offer broadband data and voice services

Coverage

Worldwide. It is expected to cover 95% of the Earth’s surface and 100% of populated areas.

Market

 It aims to provide broadband digital access at an affordable cost to information workers anywhere in the world from fixed terminals. Internet/intranet access is likely to be key markets.

 

Teledesic Constellation.

The Teledesic satellite system is a very ambitious systems. It will use 840 satellites in 21 a sun-synchronous orbital planes and provide high data rate fixed and mobile service. Data transmission is to use a fixed length [512 bt], fast packet approach.

The network consists of 16 Kbps channels, which can be aggregated to form a 2 Mbps link. Gateway connections consist of DS-3 and OC-1 links.

Phased array antennas are used to create 53.3 sq km fixed footprints. When the beam angle becomes severe, all traffic is handed off to the next satellite assigned to that cell. This requires fewer handoffs than a moving cell system. Each satellite is linked with up to 8 other satellites via a 155.52 Mbps link.

The satellites are intended to orbit in a sun synchronous orbit at 700 km and inclination of 98.2o. Each orbital plane contains 40 satellites and 4 spares.

The mobile links will operate in the Ka-band. The system can use load sharing between the satellites.

Subscriber data rates range from 16 Kbps to 2.048 Mbps. The mobile terminal antennas have a diameter ranging from 8 cm to 1.8 meters, and an average output power ranging from 0.01 W to 4.7 W.

 For Advanced Students

8.3.31 VITAsat

http://www.vita.org/

 

Status

The first satellite was destroyed during launch in 1995, and a replacement was expected to be launched by the end of 1997. In the meantime, PoSat-1 is being used on an interim basis.

Cost

US$10 million.

Orbit

Two LEO satellites orbiting at 1000km

Uplink

 

Downlink

 

Data rate

 

Owners

Volunteers in Technical Assistance,

Final Analysis Inc.

Services

Email and data transfer capability.

Coverage

Worldwide on a store and forward basis.

Market

VITAsat is designed specifically for developing countries. VITA is a non-profit making organization.

 

8.3.32 WorldSpace

WorldSpace Brochure

http://www.worldspace.com/

 

8.4   Canadian Communications Satellites

Minimum Reading

http://www.telesat.ca/

 

Anik A Series

Anik is an Inuit term meaning “little brother”. Anik A1 was launched in 1972, and was the world’s first geostationary domestic communications satellite.

 

Anik A1

Anik A2

Anik A3

Satellite Type:

Hughes HS333

Hughes HS333

Hughes HS333

Weight:

560 kg

560 kg

560 kg

Transponders:

12 C-band

12 C-band

12 C-band

Launched:

November 9, 1972

April 20, 1973

May 7, 1975

Vehicle:

Delta Rocket

Delta Rocket

Delta Rocket

Retired:

July 15, 1982

October 6, 1982

November 21, 1984

 

8.4.1  Anik-B

The Canadian Anik-B satellite is in geostationary orbit. It has 6 channels, each of which is 72 MHz wide. There is an 8 MHz guard band between each channel.

The uplink frequency band is approximately 14 - 14.5 GHz and are vertically polarized [north - south orientation]. The down link band is 11.7 to 12.2 GHz and the carriers are horizontally polarized [east - west orientation].

The satellite utilizes four antennas, each of which is used for both reception and transmission. The combined reception pattern covers almost the entire country, but the transmission pattern consists of four spot beams.

The uplink signals from all antennas are coupled from the horn antennas to the receiver section by orthomode couplers. These respond only to the vertically polarized signal. The received signal is then amplified and down converted to the downlink frequency band.

On retransmission, the odd channels can be switched by the master ground station to either the west or central west antennas. Likewise, the even channels can be switched between the east and central east antennas.

All telephone traffic on the Anik satellite is passed through transponder four and routed to the Ottawa ground station. Consequently, all telephone calls take two hops through the satellite to reach their destination.

Anik B1

Satellite Type:

RCA Astro Satcom

Weight:

920 kg

Transponders:

12 C-band

6 Ku-band

Launched:

Dec 78

Vehicle:

Delta Rocket

Status:

Retired: Dec 86

 

Anik C Series

 

Anik C1

Anik C2

Anik C3

Satellite Type:

Hughes HS376

Hughes HS376

Hughes HS376

Weight:

1160 kg

1160 kg

1160 kg

Transponders:

16 Ku-band

16 Ku-band

16 Ku-band

Launched:

Ap 85

June 83

Nov 82

Vehicle:

SST Discovery

SST Challenger

SST Columbia

Status:

Operational

Retired: Jan 98

Retired: June 97

 

Anik D Series

 

Anik D1

Anik D2

Satellite Type:

Hughes HS376

Hughes HS376

Weight:

1240 kg

1240 kg

Transponders:

24 C-band

24 C-band

Launched:

Aug 82

Nov 84

Vehicle:

Delta Rocket

SST Discovery

Status:

Retired: Dec 91

Retired: Jan 95

 

Anik E Series

When Anik E1 was launched in 1991, it was the most powerful commercial satellite in North America. It could carry 56 television channels instead of the usual 16. However, it failed in 1996.

Anik E satellites use three-axis stabilizers instead of the spin-stabilized method used on Anik A-D satellites.

Currently, the Anik E2 satellite system carries virtually all of Canada's television broadcast traffic, in addition to voice, data, and image services.

 

Anik E1

Anik E2

Satellite Type:

GE Astro 5000

GE Astro 5000

Weight:

2930 kg

2930 kg

Transponders:

24 C-band

16 Ku-band

24 C-band

16 Ku-band (2 analog TV channels each)

Launched:

Sept 91

April 91

Vehicle:

Ariane 4 Rocket

Ariane 4 Rocket

Status:

Failed 1996

Operational 2003

 

It should be noted that the site http://www.ualberta.ca/TELEHEALTH/satellite.html repots that the Anik E1 failed in 1996, however the site http://www.telesat.ca/satellites/ states that it is still operational.

Anik E2 EIRP Ku Contours

Anik E2 C Band Contours

 

Anik F1

Minimum Reading

http://www.telesat.ca/satellites/anikf1.html

 

The new Anik F1 satellite is expected to be in service in the year 2000 and provide coverage throughout North and South America. It will have 48 Ku-band and 36 C-band transponders.

Satellite Type:

HS 702

Weight:

5200 kg

Transponders:

36 Ku-band

48 Ku-band

Vehicle:

Ariane 4 Rocket e

Status:

Under construction

Service Life:

15 years

 

Nimiq

Minimum Reading

http://www.telesat.ca/satellites/nimiq.html

 

Nimiq, an Inuit word for an object or force that unites things together, will be Canada’s first DBS and will contain 32 Ku-band transponders.

Satellite Type:

LM A2100AX

Weight:

3600 kg

Transponders:

32 Ku-band

Vehicle:

Russian Proton D-1-e

Status:

Operational

Service Life:

12 Years

 

8.4.2  MSAT

MSAT is a geostationary satellite that provides mobile telephone, radio, facsimile, paging, position location and data communications.

http://www.tmi.ca/

 

Status

Operational.

Cost

 

Orbit

HS601 GEO satellite. MSAT is providing back-up capacity for AMSC. Service life expected to be 12 years

Uplink

User frequency: 1.6315 - 1.6605 GHz

Feeder frequency: 13.0 - 13.15 & 13.2 - 13.25 GHz

Downlink

User frequency: 1.53 - 1.559 GHz

Feeder frequency: 10.75 - 10.95 GHz

Data rate

Data rate: 4800 bps

Owners

TMI Communications, Telesat Canada GTIS, Glentel, Infosat, Mobility Canada Satellite.

Services

Mobile & fixed voice, fax, data.

Coverage

North and Central America

Market

Targeting high end-users that need communications in remote areas.

 

MSAT uses the HS 601 satellite bus.

It can support 2000 channels, depending on the type of antenna and bandwidth assigned. The L-band is used to communicate between end-users and the satellite. The 29 MHz L-band transponders are divided into eight channels. The satellite L-band EIRP is 57.3 dBw.

Four L-band spot beams cover North America and a separate beam serves Alaska and Hawaii. The Caribbean beam includes Puerto Rico, the U.S. Virgin Islands, and Mexico.

Ground stations use Ku-band to communicate with the satellite and each other. The satellite antenna diameter is 0.75 meters and has an EIRP of 36 dBw.

Power is provided by a 3 kW solar panel array and a 4 kW nickel-hydrogen battery. The satellite uses 3 axis stabilization and has a design life span is about 12 years

 

L-Band

Ku-Band

Main Transponders

16

1

Backup Transponders

4

2

Power [watts]

38

100

EIRP [dBw]

57

37

 

The transmission bit rates are 6400 bps for voice and 2400/4800 for data.

8.5   GPS

The Global Positioning System is a communications system of sorts. The system consists of orbiting radio stations broadcasting on the L1 and L2 bands, and is capable of identifying the location of a receiver.

It consists of 21 active satellites. Three satellites are in a parking orbit, and 4 on the ground as spares. It is expected that 4 to 10 satellites will be in the sky anywhere in the world at one time.

GPS Constellation

These satellites are in circular orbits at an altitude of 20,200 Km, and travel at about 4 Km per second.

GPS broadcasts two pseudo-random binary codes: the C/A code and P code. The P (precise) code has a 267-day long sequence, and is broadcast on both L bands. It consists of weeklong segments, and each satellite is given a portion of it to broadcast. This supports position accuracy to within 10 meters.

The C/A (clear access) code, is used for coarse acquisition has a one millisecond long sequence and is broadcast on the L1 band. It was meant for commercial applications and was to be accurate within 100 meters. In practice, the C/A code allows positioning to within 20 meters. Since this is perceived as a military threat, an artificial clock error has been introduced to reduce the accuracy to 300 meters.

Surveyors have developed sophisticated techniques to get around these restrictions and can determine an accuracy of less than a meter. This requires using two receivers used to make differential carrier wave measurements, and a great deal of time to take the satellite readings.

To determine position, the time delay to a at least 3 satellites must be made. In practice, a fourth satellite is needed, to help compensate for slight errors.

 For Advanced Students

8.5.1  GLONASS

This Russian military system, which consisting of 24 satellites in 3 orbital planes at an altitude of 19100 Km is plagued with financial difficulties. As of 1999, there were only 13 operational satellites.

GLONASS Satellite

GLONASS Orbits

GLONASS Fact Sheet

http://www.rssi.ru/SFCSIC/SFCSIC_main.html

http://www.nz.dlr.de/gps/glonass.html

http://www.oso.chalmers.se/~geo/glonass.html

 

8.5.2  Galileo

Satellite

http://www.galileo-pgm.org/

 

This is a non-military European initiative. It is expected to be operational by 2008. There are two different proposals being put forward:

9 geostationary and 21 MEO satellites (24000 Km) or

30 MEO satellites

There are three service offerings being considered:

OAS – Open Access Service, a free service offered to the general public

CAS 1 – Controlled Access Service Level 1, a fee-paying service for commercial applications

CAS 2 - Controlled Access Service Level 2, a fee-paying service for military and safety-critical applications

8.6   Satellite Microwave Channels

8.6.1  Access Methods

There are three techniques used to gain satellite access:

FDMA - frequency division multiple access

TDMA - time division multiple access

CDMA - code division multiple access

FDMA is a simple where each ground terminal is assigned specific up and downlink frequencies. The most common modulation method is FM. Although this requires more bandwidth than AM, it has a better S/N ratio and constant power level.

Since the transponder and channel bandwidth is fixed, only a limited number of customers can gain access. To increase utilization, satellites often have multiple spot beams. This allows frequencies to be reused in different parts of the service area,

With TDMA, each ground terminal is assigned a time slot. As demand increases, more time slots can be added, thus gradually slowing down the overall response time. This creates a soft limit to the maximum number of customers that can be handled. If the customer is made aware of the delay, they can make the decision to either wait in the queue or to try again at some other time.

The data frame period is usually a multiple of 125 mSec to correspond to the PSTN.

CDMA is sometimes referred to as SSMA. Individual radio carriers can be spread out over the entire satellite bandwidth. This would normally prevent any other station from using the facility, but there are ways of minimizing this conflict:

DS–CSMA: direct sequence CSMA - the station address is superimposed on the carrier along with customer data.

FH–CSMA: frequency hopping CSMA - the station address is used to continually change the carrier frequency.

8.6.2  Satellite Frequency Bands

The C-band occupies the 4 to 8 GHz frequency range and generally requires a 2-3 meters antenna. The Ku-band is from 11 to 17 GHz band and uses 0.5-meter antennas. The Ka-band goes from 20 to 30 GHz and uses even smaller antennas.

Band

Uplink [GHz]

Downlink [GHz]

Comments

L

.821 - .825

.866 - .870

MSAT

C

5.9 – 6.4

3.7 – 4.2

Fixed ground stations

X

7.9 – 8.6

7.25 – 7.75

Military mobile radio

Ku

14 – 14.5

11.7 – 12.2

Broadcast and fixed point

Ka

27 – 30

30 – 31

17 – 20

20 – 21

 

V/Q

50 – 51

40 – 41

41 – 43

Broadcast and fixed point

V

54 – 58

59 – 64

54 – 58

59 – 64

Inter-satellite

 

Most communication satellites are simply high altitude repeaters. In the past, ground stations performed all routing and switching functions. Newer satellites can sometimes perform these functions, thus reducing transmission delay.

Typical C-Band Satellite Characteristics[11]

 

Type of Coverage

Parameter

Global

Regional

National

Tx Antenna Gain [dBi]

17 - 19

21 - 25

28 - 32

Rx Antenna Gain [dBi]

17 - 19

21 - 24

30 - 34

EIRP [dB]

22 - 24

26 - 31

30 - 34

Rx Noise Temp [oK]

8000 - 2000

800 -  2000

800 - 2000

G/T [dB/oK]

-17 to -14

-12 to -5

-3 to +5

 

Typical C-Band Earth Station Characteristics

 

Type of Coverage

Parameter

Global

Regional

National

Antenna Size [m]

4.5 - 32

4.5 - 25

3 - 30

Tx Antenna Gain [dBi]

47 - 64

47 - 62

43 - 63

Rx Antenna Gain [dBi]

43 - 61

43 - 59

40 - 60

EIRP [dBW]

46 - 95

46 - 74

45 - 84

Rx Noise Temp [oK]

50 - 150

50 -  150

50 - 200

G/T [dB/oK]

23 to 41

23 to 38

17 to 41

Tx Power [kW]

1 - 12

0.3 - 3

0.005 - 1

 

The high power and frequency characteristics of Ku band satellite systems, allow for the use of very small antennas. Some typical characteristics of these systems are:

Spacecraft EIRP                  35 - 50 dBW

Spacecraft G/T                   - 3 to +9 dB/oK

Earth Station G/T                14 to 45 dB/oK

Transponder Bandwidth       36 - 72 MHz

There are two basic methods used to increase satellite frequency utilization:

Beam polarization

Multiple beams

Two beams of the same frequency can be distinguished from each other if their electric fields are orthogonal. This method is often used on terrestrial digital microwave links where the fields can be horizontally and vertically polarized. Both spacecraft and earth stations require about 30 dB of isolation between the two polarizations.

An alternative arrangement is to use circularly polarized fields. These can be oriented to the right or left. These methods are effective below 10 GHz, but in the 10 – 30 GHz region, non-spherical water droplets tend to affect the polarization, and this method doesn’t work.

To minimize coupling between transponders using two polarizations, the frequency slots are interleaved so that the center of one transponder is located in the guard band of the other.

Another way to increase frequency utilization is by means of spot beams. These can be created in three ways:

Multiple antennas

Common reflector and multiple feeds

Phase shift array

Consideration must be give to the amount of spillover from one spot to another. To increase the isolation between similar carriers on different beams, polarization may be used.

Multiple beams not only make better use of the spectrum, but it also allows satellites to perform switching function from one beam to another.

8.7   Satellite Details

Satellites are comprised of a housing, power system, antenna system, command and control system, station keeping system, and transponders.

8.7.1  Satellite Construction

The stabilization system determines the satellite’s overall shape. The basic configurations are:

3-axis stabilized

Spin stabilized

Gravity gradient beam

Three-axis-stabilized satellites contain gyroscopes rotating at 4,000 to 6,000 rpm and often resemble a box. Since the body remains fixed with respect to the earth, the antenna does not rotate. However, the solar cells, must rotate since they must always the sun.

Spin stabilized satellites are generally cylindrical and rotate at 60 - 70 rpm. Solar cells are mounted on the surface and therefore do not require pointing. However, the antenna must be decoupled from the satellite.

Gravity gradient satellites extend a large boom towards the earth, and rely upon gravity to keep t pointing down.

The vast majority of satellites are powered by solar cells. These have a conversion efficiency of 15 - 20%. When the satellite is eclipsed by the earth, nickel-hydrogen batteries supply power.

Satellite antennas must support tracking, telemetry, and command functions in addition to telecommunications traffic. If TT&C is lost, the satellite is lost.

TT&C systems monitor the satellite operating parameters, telemetry circuits, interpret commands, and control the operation of the satellite.

Satellites will drift out of its orbital slot because of the gravitational effects of the sun, moon, and earth.

They are repositioned by hydrazine gas thrusters. When the gas is gone, the satellite will drift and be lost. This is what determines the life expectancy of most satellites.

The whole purpose of a communications satellite is to support a transponder or repeater. Such a satellites may have 12 - 24 transponders with an output power of 5 to 10 watts.

8.7.2  Galaxy Satellites

Many Galaxy satellites are versions of the Hughes HS 376 communications satellite. Each has 24 transponders in the 6/4 GHz band. Most Galaxy satellites are used for television.

Galaxy 393

Galaxy 601

Galaxy XI

This is based on the Hughes 702 design.

Cu Band

24 x 36 MHz – 20 Watt Output

Uplink 5.925 - 6.425 GHz

Downlink 3.700 - 4.200 GHz

Ku-band

24 x 36 MHz – 75 Watt Output

16 x 27 MHz – 140 Watt Output

Uplink 14.0 - 14.500 GHz

Downlink 11.700 - 12.200 GHz

Galaxy XI Footprint

 

8.8 NASA Satellites

TDRS

Minimum Reading

http://samadhi.jpl.nasa.gov/msl/QuickLooks/tdrssQL.html

http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/sts-jsc-comm.html

http://www-pao.ksc.nasa.gov/kscpao/nasafact/tdrs.htm

http://www.gsfc.nasa.gov/gsfc/earth/tdrs/presskit.htm

http://spaceflightnow.com/atlas/ac139/000626tdrsh.html

http://nmsp.gsfc.nasa.gov/tdrss/tdrshij.html

http://nmsp.gsfc.nasa.gov/tdrss/oview.html

http://www.astronautix.com/craft/tdrs.htm

 

 

 For Advanced Students

8.9 Satellite Launch Vehicles

•There are several different launch vehicles:

Boeing Delta-5

http://www.boeing.com/defense-space/space/delta/deltahome.htm

Lockheed Martin Atlas rocket

http://www.lmco.com/

Sea Launch

http://www.sea-launch.com/

Pegasus air-launched vehicle

http://www.orbital.com/

Russian Khrunichev Proton rocket

European Ariane rocket

http://www.arianespace.com/

China’s Great Wall Long March 2C

Assignment Questions

 

Quick Quiz

1.  VSAT networks use satellites placed in [geostationary, polar] orbits.

2.  MEOS systems use highly elliptical orbits. [True, False]

3.  Although SPADE is a FDMA system, it uses TDM CSC signaling. [True, False]

4.  LEOS satellites travel [faster, slower] than MEOS satellites.

5.  The ratio G/T is unitless. [True, False]

Analytical Problems

Composition Questions

It may be necessary to do some research to answer some of these questions.

1.  What is the furthest north that a geo-stationary satellite ground station can be placed?

2.  Define EIRP.

3.  List three applications for PCSS systems.

4.  What are the two basic methods of code division multiple access?

5.  Check the internet for the latest information on the various satellite systems mentioned in this section.

For Further Research

 

Gagliardi, Robert M; Satellite Communications, Lifetime Learning Publications, Belmont, California, 1984

Prichard & Sauulli; Satellite Communications Systems Engineering

MSAT Phase B Final Report; Dept. of Communications Gov’t of Canada, Cat. No. Co22-77/1987E

Special Series on VSAT; IEEE Communications Magazine, July, September 1988

Series on Satellite Communications; MSN & CT November 1986

“Satellite Communications”, Electronics & Wireless World December 1985

“Communications Satellites move to Higher Frequencies”, High Technology  November 1984

Special Series on Satellite Communications, IEEE Communications Magazine May 1984

“Air and Sea Rescue via Satellite Systems”, IEEE Spectrum March 1984

 

Web-sites:

http://www.spacenet.com/

http://www.looksmart.com/eus1/eus317829/eus317861/eus65317/eus87531/eus149569/eus149572/r?l&

http://www.satsig.net/index.htm

http://www.atmdigest.com/satellit.htm

http://www.satcomms.com/

http://www.lland.demon.co.uk/sisfiles/sis.html

http://www.comlinks.com/

 

Satellite Industry Association

http://www.sia.org/index.htm

http://www.skyreport.com/index.htm

http://www.comsat.com/

http://itre.uncecs.edu/misc/sj/sj.html

http://www.funet.fi/index/esi/skyguide.html

http://www.funet.fi/index/esi/satnews.html

http://www.funet.fi/index/esi/TELE-Satellite.html

http://www.tele-satellit.com/tse/

http://www.satellitetelephone.com/

http://www.satnews.com/

http://www.fas.org/spp/index.html

http://members.aol.com/wsnspace/

http://www.nasa.gov/hqpao/space_agencies.html

http://www.yahoo.com/Government/Research_Labs/NASA/

 

ICO:

www.i-co.co.uk/

http://www.nec.com.au/ico1.htm

 

Globalstar:

http://www.globalstar.com/

www.wp.com/mcintosh_page_o_stuff/globals.html

 

Iridium:

www.iridium.com

 

Teledesic:

www.teledesic.com

 

Canadian Satellites

http://www.cancom.net/

http://www.telesat.ca/

 

US Satellites

http://www.ussbtv.com

 

European Satellites

http://www.funet.fi/index/esi/

 

DBS

http://www.primestar.com/

http://www.lookup.com/Homepages/95191/cvn.html

http://www.dbs-online.com/

http://www.directv.com/

http://www.echostar.com

http://www.expressvu.com

http://www.dbsdish.com/

 

Astasat

http://www.astrasat.co.za/index.htm

 

Hughes

http://www.hcisat.com/

 

Space Innovations Ltd.

http://www.sil.com/

http://www.sat-net.com/uk-satellite/

http://www.intelsat.com/

http://www.panamsat.com/

http://www.tdrss.com/

http://www.loralskynet.com/

http://www.comlink.com/satellite.html

http://www.comlinks.com/satcom/satmenu.htm

 

Aries

http://www.llnl.gov/gonii/aries/aries.html

 

Space Systems Loral

http://www.ssloral.com/

 

Satellite Communication Systems

http://www.satellite-commsys.com/

http://www.casbaa.com/frameset.htm

 



[1]     Alcatel Telecommunications Review 4th Quarter 1999.

[2]     http:/www.atek.com/satellite/table

     Very Small Aperture Terminals

[3]     Telecommunications, March 1993

[4]     Communications News, November 1994

     Great Atlantic and Pacific Tea Company

     Point of Sale

     World Administrative Radio Conference, held in Malaga-Torremolinas, Spain in 1992

[5]     Satellite-based Personal Communication Services, Telecommunications, December 1993

     Personal Communications Satellite Services

[6]     TE&M, Oct 1, 1993

[7]     Iridium: Key to Worldwide Cellular Communications, Telecommunications, October 1991

     Public Telegraph and Telephone

[8]     TE&M, Feb 15, 1993

     An element with 77 orbiting electrons

[9]     TE&M, Feb 15, 1993

[10]    Telecommunications International, March 1993

     GLObal NAvigation Satellite System

     Spread Spectrum Multiple Access

[11]    Electronic Communications Handbook, A. F. Inglis, ed.