Tutorial Satellite Communication

By Kamran Ahmed

Institute of Information Technology

University of Sindh, Pakistan

Contents

n What is satellite communication 1. Overview of Satellite n The origin of satellite Systems n Basic satellite System n System design Considerations

n Advantages of Satellite / Applications

n Limitation of Satellites

n Frequency Allocation

What is Satellite Communication… Cont... n A communication satellite is basically an electronic communication package placed in n Communication satellite are off-course orbit whose prime objective is to initiate or assist only one means of telecommunication another through space. transmission. The traditional means n Satellite communication is one of the most include copper wire and microwave point- impressive spin-offs from the space programs to-point links. Newer techniques involves and has made a major contribution to the use of optics either point-to-point infrared pattern of international communication. or fiber optics. Point-to-point radio system n The information transferred most often such as short wave radio may also be correspondence to voice (telephone), video used. (Television) and digital data.

1 Elements of Satellite The origin of satellite Communications n The concept of using object in space to reflect signals for communication was proved by Naval Research Lab in Washington D.C. when it use the Moon to establish a n The basic elements of a communication satellite very low data rate link between Washington and Hawaii in late 1940’s. service are divided between; n Russian started the Space age by successfully launching nSpace Segment SPUTNIK the first artificial spacecraft to orbit the earth, which transmitted telemetry information for 21 days in nGround Segment Oct. 1957. n The American followed by launching an experimental n The space segment consist of the spacecraft & satellite EXPLORER In 1958. launch mechanism and ground segment n In 1960 two satellite were deployed “Echo” & “Courier” comprises the earth station and network control n In 1963 first GSO “Syncom” center of entire satellite system. n The first commercial GSO (Intelsat & Molnya) in 1965 these provides video (Television) and voice (Telephone) for their audience

Satellite Communications System Concept Transponder

Uplink Down Link downlink downlink uplink uplink IDU RFT RFT IDU RF Transmit Earth Station Receive Earth IRRADIUM Station Earth station (site A) Earth station(site B)

Propagation Delay Applications n Communication n Weather telecast

(truncking call) n Navigation n Teleconference n GPS n Telemedicine n Security/Calamity n TV Broadcasting monitoring n Data communication n Standard Time n Telemetry(TEC, n military Single Hop 270 ms remote sensing etc) Double Hop 540 ms

2 Ground Station _ Anatomy Electromagnetic Spectrum

IFL Indoor Unit Outdoor Unit Antenna (IDU) (ODU) Sub-System

70/140 C/Ku MHz

Satellite Operating Frequency Radio Frequency Bands Bands

Band Number Band Name Frequency Range Metric Subdivision Frequency Range (GHz) Band Category 4 VLF, Very low frequency 3-30 KHz Myriametric waves 5 LF, Low frequency 30-300 KHz Kilometric waves 0.39-1.55 L MSS 6 MF, Medium frequency 300-3000 KHz Hectometric waves 7 HF, High frequency 3-30 MHz Decametric waves 1.55-5.2 S FSS & BSS 8 VHF, Very high frequency 30-300 MHz Metric waves 3.9-6.2 C FSS 9 UHF, Ultra high frequency 300-3000 MHz Decimetric waves 10 SHF, Super high frequency3-30 GHz Centimetric waves 5.2-10.9 X Military 11 EHF, Extra high frequency 30-300 GHz Decimillimetric waves 10.9-36.0 K FSS & BSS 15.35-17.25 Ku FSS & BSS 18.3-31.0 Ka FSS

Early Satellites Early Satellites

Satellite Launching Date Country/Organization Type Height (miles) Comments Satellite Launching Date Country/Organization Type Height (miles) Comments

RELAY 1962 USA/RCA & NASA Active Duplex 942-5303 4.2/1.7 GHz satellite designed to Explorer 1958 USA/NASA Broadcast 110 to 920 Very short life; Noted for carry telephone signals. re-broadcasting an on-board taped message from president SYNCOM 1963 USA/NASA Active Duplex Geostationary First Geostationary communication Eisnhour satellite used to transmit television signals from the Tokyo Olympics. ECHO 1960 USA/NASA Passive 1000 100-Foot diameter plastic balloon with an aluminum coating which MOLNIYA 1965 U.S.S.R Active Duplex High altitude First Soviet communication satellite reflect radio signals elliptical used a high altitude elliptical orbit. COURIER 1960 Department of defense Store & Repeat 600-700 First radio repeater satellite. It EARLY 1965 INTELSAT/COMSAT Active Geostationary First commercial communication accepted and stored upto 360,000 BIRD satellite; served the Atlantic ocean teletype words as it passed region; capacity to carry 240 voice overhead and then broadcast to channels ground stations further along the orbit; only operated for 17 days. INTELSAT 2 1966 INTELSAT/COMSAT Active Geostationary First multiple access commercial satellite with multidestination TELSTAR 1962 USA/AT&T Active Duplex 682-4030 First satellite to receive and transmit capability simultaneously; Operated in 4/6 GHz band

INTELSAT 3 1968 INTELSAT/COMSAT Active Geostationary 3 generation designed to carry 1200 voice circuits

3 Early Satellites Satellite Services

Satellite Launching Date Country/Organization Type Height (miles) Comments n The ITU has grouped the satellite services in to three main groups INTELSAT 4 1971 INTELSAT/COMSAT Active Geostationary COMSAT’s 4th generation; n designed to carry 6000 voice Fixed Satellite Services (FSS) circuits. n Broadcast Satellite Services (BSS) ANIK 1 1972 Canada/Telesat Active Geostationary World’s first domestic satellite; 5000 n Mobile Satellite services (MSS) voice circuits capacity.

WESTAR 1974 USA/Western Union Active Geostationary First US domestic satellite

Asiasat 2 Space Segment

n Space segment consist of a satellite in suitable orbit.

n Space segment classified on the basis of orbit; n LEO n MEO

n HEO n GEO & GSO

Ground Segment System Design Consideration

n The ground segment of each service has n Services or Application distinct characteristics. n Selection of RF Band n Services like; n Finance n FSS n Further technical design considerations are:- n BSS n Optimal modulation, coding scheme, type of service, n MSS permitted earth station size and complexity, shape of n Maritime, Aeronautical & Land base service area, landing rights, state of prevailing n DBS technology related both to spacecraft and ground n Etc. station.

4 Advantages of Satellite Limitation of Satellites

n Wide band capability n Wide area coverage readily possible n High initial investment

n Distance-insensitive costs n New investment require in Ground n Counter inflationary cost history Segment n All user have same access possibilities n Short life time (7-10 years) n Point to point, point to multipoint (broadcast) and multipoint to point (data collection) are all n Spectrum crowding possible n Regulatory aspects n Inherently suited for mobile application. n Launch vehicle reliability n Compatible with all new technologies

n Service directly to the users permises

Frequency Allocations Frequency Allocation and Regulatory Aspects n Frequency bands for satellite services are shared with terrestrial services. n Satellite signal strength is constrained to avoid interference by it to n Domestic others. e.g. Federal communication Commission (FCC) n Thus a large antenna and sensitive receiver are needed at the earth National Telecommunication and Information Administration (NITA) station. In Pakistan, PTA (Pakistan Telecommunication Authority) n Frequency sharing techniques are an important study area. n Many satellites have to share a limited frequency band (and limited n International orbital arc) thus coordination in frequency and orbital location is International Telecommunication Union (ITU) important. n Formed in 1932 from the International Telegraph Union n Consists of over 150 members nations n Frequency allocation are done by international agreements n World Administrative Radio Conference (WARC) n International Radio Consultative Committee (CCIR) consists of 13 study groups.

ITU Regions ITU Regions (Continued)

ITU divides the surface area of the earth into three regions for the n Region 3: Indian Ocean Region purpose of frequency allocation Pakistan-India Sub-continent , South East Asia & Australia n Region 1: Pacific Ocean Region North and South America Greenland

n Region 2: Atlantic Ocean Region Europe Africa Middle East Central Asia

5 Frequency Allocations to Satellite Services The International Telecommunications Union

Examples of Satellite Radio Services: - Fixed Satellite Service FSS - Mobile Satellite Service MSS - Broadcast Satellite Service BSS - Radio Navigation Sat. Serv. RNSS - Radio location Sat. Service RSS - Space Operation Service SOS - Earth observation Sat. Serv. ESS - . . .

In total more than 18 radio services

The International Telecommunications Union The International Telecommunications Union

A license is required by every operator in order to Artikel S5 der Radio Regulations operate a satellite system nationally; a licence may only be acquired if: Region 1 Region 2 Region 3 - the operator can show that he has a contract with 19.7 - 20.1 GHz 19.7 - 20.1 GHz 19.7 - 20.1 GHz the system owner to be his service provider FIXED-SATELLITE FIXED-SATELLITE FIXED-SATELLITE - the frequencies for the system have been cleared / (space-to-earth) (space-to-earth) (space-to-earth) coordinated / notified Mobile-Satellite MOBILE-SATELLITE Mobile-Satellite - that system is fully registered with the ITU (space-to-earth) (space-to-earth) (space-to-earth) -the operator has workers registered as operators A licence will be cancelled if: S5.524 S5.524, S5.525, S5.526 S5.524 S5.527, S5.528, S5.529 - there are no more registered operators to work the system - the service provider has breached ‘data protection laws’

Before the lecture

n Try to find out more by reading: n http://ctd.grc.nasa.gov/rleonard/regconte 2. Orbit and Launching Methods nts.html n http://www.aticourses.com/iridium.htm

n http://www.aticourses.com/global_positio ning_system.htm

n http://www.mlesat.com/Article9.html n http://www.mlesat.com/tutorial.html

6 Orbits Satellites

n Circular orbits are simplest Several types n Inclined orbits are useful for coverage of n LEOs - Low Earth Orbit equatorial regions n MEOs - Medium Earth Orbit n Elliptical orbits can be used to give quasi stationary behaviour viewed from earth n HEOs – Highly Elliptical Orbit n using 3 or 4 satellites n GSO - Geostationary Earth Orbit n Orbit changes can be used to extend the life of satellites

LEO MEO

n Low Earth Orbit n Medium Earth Orbit n 200-3,000 km n 6,000 – 12,000km n High orbit speed n New generation n Many satellites n About 12 satellites n Predominately mobile n Voice and mobile n Iridium, Globalstar n ICO (Odyssey), Orbcomm, n (space shuttle orbit) Ellipso

Ellipso

Sub-Satellite Track of a HEO The 24 h HEO of Sirius

7 The 24 h HEO of Sirius HEOs: Molnya and Tundra

Molnya Tundra

Period 12 h 24 h Apogee 39500 km 46300 km Perigee 1000 km 25300 km Inclination 63.4° 63.4°

Satellite Orbits and Periods GEOs

Height Period Cell Visible Duration of of Orbit1 of Orbit Diameter Part of Earth # of Satellites Overflight n (km) (h) (km) % * (min) Originally proposed by Arthur C. Clarke

200 1.5 3 154 1.5 66 7 n Circular orbits above the equator 700 1.6 5 720 5.0 20 14 n Angular separation about 2 degrees - 1000 1.8 6 719 6.8 15 18 allows 180 satellites 1 414 1.9 7 806 9.1 11 22 10 000 5.8 14 935 30.5 4 130 n Orbital height above the earth about 20 000 11.9 16 922 37.9 3 300 23000 miles/35786.16km 35 786 24.0 18 100 42.4 3 24 h/d n Round trip time to satellite about 0.24 1above the surface of the earth seconds *minimum necessary for 0° elevation and 0 redundancy

GEOs (2) GEOs (3)

n GEO satellites require more power for n Since they appear stationary, GEOs do not communications require tracking

n The signal to noise ratio for GEOs is worse n GEOs are good for broadcasting to wide because of the distances involved areas n A few GEOs can cover most of the surface n Currently 329 GEO are in orbit of the earth (ref: web site provided by Johnston) n Note that polar regions cannot be “seen” by GEOs

8 The original vision and then.. n 1945 Arthur C Clark envisaged “extraterrestrial relays” n 1957 Sputnik n 3 satellites n a rush of experimental satellites in many n Period 23 h 56 min 4.091 s orbits st n Height 36 000 km above n Intelsat 1965 – 1 commercial GEO service equator n over 800 objects registered so far n Speed of flight 3.074 km/s

GEO - geostationary earth orbit the view from 36,0000km

n characterised by:

n delay (echo) ~0.5sec return n high power n 5-7 years life

n global and spot beams n C and K band (4-6Ghz and 12-14Ghz)

n 2 – 3o spacing n Currently more than 200 GEO satellites in operation

Earth coverage with 2 spacecraft

90 some GEO’s above us

70

50 n Optus * 3 30 n AsiaSat * 3 10

-10 n PAS * 2

-30 n Intelsat * 7

-50 n Inmarsat * 2 -70 Some Service Providers:

-90 n Palapa * 2 Netspeed Austar Optus Telstra iHug -170 -150 -130 -110 -90 -70 -50 -30 -10 10 30 50 70 90 110 130 150 170 Newskies MediaSat NTL Heartland Xantic and others Stratos Coverage of the inhabited world except for Polynesia

9 National and Regional Systems Satellite Footprints

Satellite beam their signals in a straight path to the earth. Th e satellite focus these microwaves signals onto the specified portions of the earth’s surface to most effectively use the limited powe r of their transponders. These focused signals create unique beam patterns called “footprints.”

Types of footprints: n Global beam footprint n Hemispheric Beam Footprint n Zone Beam Footprint 1 Anik, Canada 6 Telecom, France 11 Asiasat, East Asia 2 Morelos, Mexico 7 Kopernikus, Germany 12 CS, Japan 3 Panamsat, Americas 8 Italsat, Italy 13 Palapa, Indonesia 4 Brasilsat, Brazil 9 Arabsat, Arab League 14 Aussat, Australia 5 Eutelsat, Europe 10 Insat, India

Satellite Footprints Satellite Footprints

Satellite Footprints Satellite Footprints

10 Characteristics of a Geostationary Satellite Key Input Data... Orbit

Bands: n Eccentricity (e) 0 C-Band ( ) n Inclination of the orbital plane (i)0º Ku-Band ( ) n Period (T) 23h 56m 4s

n Semi-major axis (a) 42164 km

n Satellite altitude(R) 35786 km Beams: n Satellite velocity (Vs) 3075 m/s Global ( ) Hemi ( ) 2 3 14 3 2 Zone ( ) F=GMm/r T=2pÖa /m m=Gme=3.986x10 m /s Spot ( ) e=c/a V= m(2/r-1/a) m/s

The GEO The GEO Elevation , distance to the satellite

d d Ro e Ro e z z

pR o pR o

2 2 2 Dlon = Longitude - Longitude Kgrav = m Me G / r Kzent = m r ww , = m v / r E/S Satellite Dlat = Latitude - Latitude Angular velocity ww = 2pp / T, T Period, v velocity E/S Satellite

Kgrav = Kzent und Space angle a: cos( a ) = cos ( Dlon ) * cos( Dlat ) 2 2 2 2 m Me g / r = m r ww bzw. Me g / r = r ww Distance d: d = R Ö 6.6112 – 2 * 6.611 * cos a + 1 3 2 2 o r = Me g T / ( 2pp ) Elevation e: sin( e ) = [ 6.611 2 R 2 – R 2 – d2 ) / ( 2 R d ) ] The period T of the circular orbit (r in km, m = 398 601.8 km3/s2) is o o o T = 2 ppÖÖ r 3 / m = 9.952 10-3ÖÖ r 3 / km in Seconds Test: a = 81.3° d = 41680 km and e = 0° p = 6.611 a = 0° d = 35787 km and e = 90°

The inclination (1) The inclination (2)

. .

) )

The inclination: orbit remains geosynchroneous, After 18 years some 15° of inclination will have built up; 24 h; satellite moves North/South; now the inclination reverses and decreases by 0.8°/year; inclination builds up 0.8°/year if satellites with <15° inclination are geostationary by law. The inclined plane The inclined plane not corrected contiuously

The equatorial plane The equatorial plane

11 Transfer Orbits C-Band satellites in GEO

GEO

Drift Orbit 3-Achsen Stabilisierung Legende Restpaneelentfaltung Sonnenorientierung im Orbit

1. Zündungsende im Bau Transfer Orbit 2. Zündungsende ITU Appl.

Eklipse 3. Zündungsende 1. Apogäum SONNE Legend

langsame Akquirierung on orbit Bedrallung Abtrennung under constr 1. Zündungsbeginn 3. Zündungsbeginn ITU Appl. Akquirierung 2. Zündungsbeginn Entdrallung (1995)

Erdorientierung

Ku-Band satellites in GEO C and Ku-Band satellites in America

Legende im Orbit im Bau ITU Appl.

Legend on orbit under constr ITU Appl.

(1995)

Early experiments ECHO 1

n US Navy bounced messages off the moon n ECHO 1 “balloon” satellite - passive n ECHO 2 - 2nd passive satellite n All subsequent satellites used active communications

n Photo from NASA

12 Early satellites TELSTAR

n Relay

n 4000 miles orbit n Telstar

n Allowed live transmission across the Atlantic n Syncom 2

n First Geosynchronous satellite

n Picture from NASA

SYNCOM 2 Major problems for satellites

n Positioning in orbit

n Stability

n Power

n Communications

n Harsh environment

n Picture from NASA

Satellite Orbits comparison chart Features GEO MEO LEO Height 36,000 6,000- 200- 3000 (km’s) 12,000 Time per 24 5 - 12 1.5 Orbit (hrs) Speed 11,000 19,000 27,000 (kms/hr) Time 250 80 10 delay (ms) Time in Always 2 - 4 hrs < 15 min site of Gateway Satellites 3 10 - 12 50 - 70 for Global Coverage

13 Mega LEOs, MEOs, HEOs, and GEOs back to GEOs

1 TELEDESIC of microSoft with 288 LEOs at Ka -Band 2 V -Band Supplement of TELEDESIC/microSoft with 72 LEOs im Q-Band n given current-generation LEO’s and MEO’s 3 GS -40 of Globalstar LP with 80 LEOs at Q-Band 4 M-Star of Mororola with 72 LEOs at Q-Band are predominately used for mobile voice 5 LEO ONE of LEO ONE Corp. with 48 LEOs at Q-Band and low-speed data services (MPSS) 6 ORBLINK of Orblink LLC with 7 MEOs in Q-Band 7 SkyBridge of ALCATEL witt 64 LEOs and 9 GEOs in Ku-Band n good voice coverage for remote regions 8 WEST of MATRA with 10 MEOs and 12 GEOs in Ka-Band n adjunct to GSM mobile networks ~ Globalstar 9 GESN of TRW with 15 MEOs and 4 GEOs in Q-Band 10 CELESTRI of Motorola MOT with 63 LEOs and 10 GEOs in Ka -Band 11 SpaceWay of Hughes Communications with 20 LEOs and 16 GEOs in Ka -Band 12 StarLynx of Hughes Communications with 20 MEOs and 4 GEOs in Q-Band 13 DenAli Telecom LLC PenTriad in HEO im Ku-, Ka -, V- and W-Band

what is SkyBridge? the future n SkyBridge is an Alcatel controlled company planning to establish a constellation of 80 satellites to provide broadband data n continual development in VSAT (GEO) technology communications direct to business & residential premises. n bandwidth gains

n multiple services = choice n Satellites are Low Earth Orbit (LEO) at an altitude of 1500 km n Broadband LEOs n offers “last mile” broadband access from n Teledesic

n fixed and transportable terminals 2004 n 64k – 2M – and above (Gb) n no long-haul trunking capability - connects n 288 satellites n 2005 launch?? users to terrestrial gateway n SkyBridge n System cost is approx US$4.8bn n 80 satellites n 2004

broadband LEO – low latency Launching

36 000 km GEO : 500ms Astrolink Step 1: satellite is released in the Low Earth Orbit by launch Intelsat vehicle Spaceway

LEO : 30ms 1 500 km SkyBridge Teledesic Step 2: The Payload Assist Module (PAM) rocket fires to place the satellite into the geostationary transfer orbit (GTO)

LEO round-trip propagation time comparable to terrestrial

14 Launching (Continued) Launching (Continued)

Step 3: Several days after the satellite gets into the GTO the Step 4: Orbital Adjustment by firing the AKM to achieve a circular Apogee Kick Motor (AKM) fires to put the satellite into a geosynchronus orbit nearly circular orbit.

Launch Vehicles Launch Vehicle

Launch Atlas II Delta II Ariane-4 Proton Long H-2

Vehicles March-3

Country USA USA Europe Russia China JAPAN

Gross 460 t 680 t 202 t 260 T Weight

Boast to 3636 Kg 1,819 Kg 2,200 Kg 2,000 Kg 650 Kg 2,200 kG GTO

Summary of Launchers Launch Vehicle

15 Sea Launch At the Equator

Der Äquator The equator

11 day travel, 3 days on site, 9 days back 1. and 2. stage fueled on launch site; 3. stage and satellite fu eled in Long Beach

Sea Launch The Launch Service Alliance

Lift-Off! Up to 6 t 3000 m deep water Commander is 5 km away for launch

ArianeSpace, Boeing Launch Services, and Mitsubishi Heavy Industries mutual backup to mitigate schedule risks, range issues, etc.

Types of Launches Summary of Launchers International Launch Services, ILS Lockheed Martin, USA, Land Launch Khrunichev, RUS, Energia, RUS The Evolution: since the 60ies Atlas-IIARlo , Proton-Mhi Baikonur Launch Site

Sea Launch Rail Launch since the 90ies since the 70ies

Air Launch since the 80ies

16 Common Abbreviations

Anatomy of a Satellite Orbits: GEO = Geostationary Earth Orbit HEO = Highly inclined Elliptical Orbit A communication satellite consists of the following subsystems: MEO = Medium altitude Earth Orbit n Antenna_For receiving and transmitting signals. LEO = Low altitude Earth Orbit n Transponder_It contains the electronics for receiving the signals, IGSO = Inclined Geo-Synchroneous Orbit amplifying them, changing their frequency and retransmitting the m. HAP = High Altitude Platform n Power Generation and conditioning subsystem_For creating power and converting the generated power into a usable form to operate Services: the satellite. BIG = Voice Telephony n Command and Telemetry_For transmitting data about the satellite (status, health etc.) to the earth and receiving commands from Super = Voice telephony into mobiles from GEO earth. Little = Data only, typically store and forward n Thrust subsystem_For making the adjustments to the satellite Mega = Mega-bit/s services orbital position and altitude. DBS = Direct Broadcast satellite television Service n Stabilization subsystem_For keeping the satellite antennas point ing in exactly the right direction. Dab = Digital Audio Broadcast satellite service Nav = Navigation service

glossary GEO – geostationary earth orbit – 36,000km IP – Internet Protocol – the language of the MEO – Medium earth orbit – 6-12,000km Internet. The protocol stack is referred to LEO – Low earth orbit – 200-3,000km as TCP / IP Broadcast – One to many simultaneous Fixed – refers to a satellite receiver being transmission, usually associated with attached as a permanent mounting, as older style analogue transmission opposed to tracking. Multicast – In communications networks, to Mobile –Refers to a mobile satellite receiver such transmit a message to multiple as a personal communicator or mobile recipients at the same time. Multicast is phone. Usually associated with LEO and a one -to-many transmission similar to MEO services. broadcasting, except that multicasting Broadband –high speed transmission. The means sending to specific groups, threshold is arguable, but is construed as whereas broadcasting implies sending to everybody. When sending large being faster than dial-up ~ 64kbps and upwards. Some conventions suggest the volumes of data, multicast saves considerable bandwidth, because the threshold starts at 1.5 or 2Mbps. bulk of the data is transmitted once Orbit – The path of a celestial body or an artificial from its source through major satellite as it revolves around another backbones and is multiplied, or body. distributed out, at switching points One complete revolution of such a body closer to the end users. VSAT– Very small aperture terminal, refers to a 2-way – Infers forward and reverse small-dish service using a GEO satellite transmission via the satellite, usually and a large central hub, usually 6 metres but not always asymmetric, i.e. high- plus. speed download from the satellite and DTH– Direct to home. A service bypassing low speed from client to the satellite normal terrestrial infrastructure such as a latency – The time between initiating a satellite TV receiver. As opposed to request for data and the beginning of community satellite service where local the actual data transfer. A GEO satellite distribution from a satellite receiver is done has a latency of approx 256ms by cable, radio or other means. resulting in a round trip delay of about half a second (echo)

17