History Of Satellite Communications Information Technology Essay

✅ Paper Type: Free Essay	✅ Subject: Information Technology
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Communications specifically between radio stations on earth (earth stations) via a radio station set up on a spacecraft (space station) are called “satellite communication”. Satellite communication obtains different purposes such as for meteorology, radio, internet and television. Thus, this research is focus only satellite communication for television broadcasting, which transmit and receipt signal via a communication satellite (abbreviated COMSAT) – an artificial satellite stationed in space for the purpose of telecommunications.

The history of satellite communications dates back to 1945 when a paper titled “Extra-terrestrial Relays” was written by Arthur C. Clarke who first describes the principle of satellite communications with satellites in geostationary orbits – a speculation realized 25 years later. The space era started in 1957 with the launching of the first artificial satellite – SPUTNIK of the USSR. Subsequent years have been marked by various experiments including the following: the world first reflecting satellite ECHO of USA (1960), the powered relay satellite TELSTAR of Europe (1962), the first geostationary satellite SYNCOM of NASA (1963), and the world first commercial geostationary satellite INTELSAT I or Early Bird of USA (1965) [2]

In 1966, Thailand became a member (49th) of the International Telecommunication Satellite Organization (INTELSAT) to management the demand of telecommunication channels and network data. Later in 1993, Thailand was launched the first domestic communication satellite named “THAICOM 1” under concession of the Shinawatra Computer and Communications Co.,Ltd. [3] , and the latest Thai communication satellite relay in the orbit is THAICOM 5.

ECHO (b) TELSTAR (c) SYNCOM

INTELSAT I (e) THAICOM I (f) THAICOM 5

Figure 2.1 Communications Satellites

2.1.2 Satellite orbits [4]

Satellites relay in the orbit – the gravitationally curved path of an object around the Earth, which satellite orbits can be classified under three main types.

Figure 2.2 Types of satellite orbits

Types of orbits path

Equatorial Orbit: it moves along with the equinoctial line.

Inclined Orbit: it makes angle with the equinoctial line.

Polar Orbit: it moves along the North Pole and South Pole.

Types of orbits pattern

Circular Orbit: it rotates around a fixed axis.

Elliptical Orbit: it rotates in different distance from axis – the most distance called “Apogee” and the least distance called “Perigee”.

Types of orbits distance;

Low-Earth Orbit (LEO): This orbit has the least altitude from the Earth at 500-2,000 kilometer. Satellites require moving at a very high speed at 28,000 kilometer per hour to avoid being pulled out of orbit by Earth’s gravity. At LEO, satellites can cycle approximately 90 minutes around the Earth.

Medium-Earth Orbit (MEO): This orbit has altitude at 8,000-12,000 kilometer above the Earth, and satellites are placed in an Elliptical Orbit that covers the North and South Pole.

Geosynchronous or Geostationary Orbit (GEO): This orbit has the highest altitude at 35,786 kilometer, which the satellites cycle in the same direction and at the same speed as the Earth’s rotation on its axis. The satellites take 24 hours to complete a full trip around the globe. The way satellite positioned over the equator in GEO, the transmission signal appears to be direct to a specific location on the Earth.

Communications satellites in use today for television broadcasting purposes are placed in the geostationary orbit (GEO) such as THAICOM 5 of Thailand, PALAPA of Indonesia, and ASIA SAT of Hong Kong as the following advantages;

One satellite can cover almost 1/3 of the Earth’s surface, offering a reach far more extensive than what any terrestrial network can achieve

Communications require the use of fixed antennas. Since geosynchronous satellites remain stationary over the same orbital location, users can point their satellite dishes in the right direction, without costly tracking activities, making communications reliable and secure

GEO satellites are proven, reliable and secure – with a lifespan of 10-15 years

2.1.3 Satellite communications structure [5]

All elements of satellite communication structure for television transmission are identified as follow;

Geostationary satellite and back up satellite: contain one active and back up satellite for spare purpose in a constellation. Each satellite’s life is approximately 7-15 years.

Station keeping or Master control station: consists of all ground facilities for the control and monitoring of the satellites, named TTC (Tracking, Telemetry and Command) stations, and for the management of the traffic and the associated resources onboard the satellite.

Free space

Earth station: consist of antenna, high power amplifier, low noise amplifier, up converter, and down converter.

Links: contain 2 links – uplink and downlink, linkage between the earth station and communications satellites.

Terrestrial network: linkage between the earth station and user terminal, which transferred by fiber optic cable.

2.1.4 The configuration of a satellite communications system

Figure 2.3 shows an overview of satellite communication system for television broadcasting.

Figure 2.3: The satellite communications system

http://t2.gstatic.com/images?q=tbn:ANd9GcQA-iB7X7QhcjXd2mL6iGwFCGAHIicyvWH3PP2cIQOYH2it7Rg&t=1&usg=__0aw6ADL3MkplFl3F6XXdN87Cz_o=The satellite communication for television broadcasting composes of two main segments; a ground segment, and a space segment. The ground segment consists of earth stations and user terminals, which connect through terrestrial network by fiber optics. User terminals transfer their programming in base band to the earth station through terrestrial network by fiber optics to compress the size of the data – by reducing the size of the data; the provider can broadcast more channels to a satellite. Once the data is compressed, the broadcast signal is encrypted, and then the earth station will modulate and send uplink signal by microwave to a satellite in orbit. Then the satellite works as a repeater to amplifies the signal and send downlink signal back to the earth station. Next, the earth station will demodulate data back to base band and transfer back to user terminals. In case of direct to home transmission, viewers can receive data signal by their satellite dish directly. In the space segment means communications among another satellites in the orbit for different purposes.

Earth stations in Thailand

In Thailand, there are five earth stations, which owned by THAICOM CO., Ltd and CAT Telecom Co., Ltd. Both earth stations operate in similar responsibilities as below;

THAICOM Co., Ltd

“THAICOM is Asia’s leading commercial satellite operator providing advanced transmission access for information and entertainment to some of the world’s leading media and network companies, multinational corporations, and government agencies”

THAICOM provides two one-stop-shop earth stations and master control station called “Teleport and DTH Center” located in Prathumthani and Nonthaburi provinces. THAICOM Teleport and DTH Center offers comprehensive network solutions, including digital uplink system, tape play out service, compression system, downlink monitoring system, transponder service, and global digital television under the standard ISO9002 and 9001:2000. [6]

Compression Service

– MPEG-2/DVB compliance system

– CD-quality stereo audio

– Network control & monitoring

– Flexible video and audio quality

– Channel bit rate: 3-8 Mbps per channel, broadcast quality

– Compatible with any receiver

– Free-to-Air or Encryption feature

Uplink Service

– 11 or 7.2 meter antenna uplink station

– Carrier is transmitted to MCPC transponder

Tape Play Service

– BETACAM, DVCAM or DVC-PRO format

– Automatic/Manual Tape Play system

– Logo Insertion, PAL/NTSC conversion

Transponder Service

– Spectrum efficiency provides lower space segment cost per channel

– Choices of KU-band Beam, C-band Regional Beam and C-band Global Beam

– C-band receiving dish size is small, from 1.8-2.4 meters

System Integration and Global Services

– Complete end-to-end service for integrated satellite TV networks

– Consultancy services for teleport design and installation

– Turnaround and connectivity with other satellites for global coverage

http://www.catdatacom.com/images/stories/bandnersatlink.jpg

CAT Telecom Co., Ltd

“Quality Assurance and Service Efficiency”

Another three earth stations owned by CAT Telecom Co., Ltd located in Nonthaburi, Chonburi, and Ubonthani provinces. Their television transmission services are providing uplink and downlink in digital system under standard of ISO 9001 [7] . Its services can be identified below;

Distribution: receiving international program and transfer to domestic television stations.

http://satlink.cattelecom.com/catdatacom/wp-content/uploads/2010/09/tvt-distribution.jpg

Contribution: transfering domestics program to both domestics and international television stations.

http://satlink.cattelecom.com/catdatacom/wp-content/uploads/2010/09/tvt-contribution.jpg

Turnaround: receiving television programs from one satellite and then transfer to another satellite for a broader broadcasting transmission.

http://satlink.cattelecom.com/catdatacom/wp-content/uploads/2010/09/tvt-turnaround.jpg

Content Delivery: transferring television programs from program producers to television stations or cable TV

http://satlink.cattelecom.com/catdatacom/wp-content/uploads/2010/09/tvt-contentdelivery.jpg

DSNG: providing mobile broadcasting station

http://satlink.cattelecom.com/catdatacom/wp-content/uploads/2010/09/tvt-dsng.jpg

2.2 Satellite television

Telecommunication, or telecom, is the transmission of signals over long distances from one sender to another. [8]

After the development of satellite communications, many telecommunication devices such as telephone, internet, and including television have been improved and exploited in signal quality and stabilization, broader communication transmission, higher speed, and flexibility in accessibility.

Satellite television is a television system in which the signal is transmitted to an orbiting satellite that receives the signal and amplifies it and transmits it back to earth. [9]

This part illustrates communication satellites that relay in global and Thailand, and explains the evolution and identifications of Thai communication satellite, signal frequencies, angle of azimuth and elevation.

2.2.1 Communication satellites that relay in geostationary orbit [10]

Figure 2.4 shows total commercial communication satellites relay in geostationary orbit.

BSS: Boeing Satellite Systems

Figure 2.4: Commercial Communication Satellites in Geostationary orbit

Communication satellites available for Thai television broadcasting

Table 2.1 shows all commercial communication satellites relay in geostationary orbit that states the individual identification of the orbital slot and usability which Thai viewers can be received directly to home.

Table 2.1: List of communication satellites available for Thai television broadcasting

Table 2.1:

Orbital Slot Name

Usability

(Degree) HD TV TV Digital TV Analog

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177.0oW NSS 5 0 1 0

180.0oE Intelsat 701 0 89 1

169.0oE PAS 2 N/A N/A N/A

166.0oE PAS 8 N/A N/A N/A

164.0oE Optus A3 0 7 0

162.0oE Superbird B2 0 0 3

160.0oE Optus B1 0 96 1

158.0oE Superbird A 0 1 6

156.0oE Optus C1 0 192 0

154.0oE JCSAT 2A 0 3 0

152.0oE Optus B3 0 96 0

150.0oE JCSAT 1B 0 1 5

148.0oE Measat 2 0 40 0

146.0oE Agila 2 0 69 0

145.0oE Gorizont 33 0 7 0

144.0oE Superbird C 0 48 0

140.0oE Gorizont 31 0 0 1

138.0oE Telstar 18 0 116 0

136.0oE N-Star B 0 1 0

134.0oE Apstar 1A N/A N/A N/A

134.0oE Apstar 6 0 37 5

132.0oE N-Star A 0 2 0

Orbital Slot Name

Usability

(Degree) HD TV TV Digital TV Analog

124.0oE JCSAT 4A 0 93 0

122.2oE AsiaSat 4 0 19 0

120.0oE Thaicom 1A 0 6 0

118.0oE Palapa B4 0 1 0

116.0oE Koreasat 3 N/A N/A N/A

113.0oE Palapa C2 0 23 2

113.0oE Koreasat 2 0 67 0

110.5oE Sinosat 1 0 63 0

110.0oE BSAT 1A 10 3 4

110.0oE BSAT 2A 10 3 4

110.0oE N-Sat 110 N/A N/A N/A

108.2oE Worldsat 1 0 51 0

108.0oE Telkom 1 0 46 0

107.7oE Cakrawarta 1 0 46 0

105.5oE AsiaSat 3S 0 253 0

105.0oE AsiaStar 0 0 0

103.0oE Express AM 3 N/A N/A N/A

100.5oE AsiaSat 2 0 29 0

96.5oE Express AM 11 0 49 2

95.0oE NSS 6 0 175 0

93.5oE Insat 3A 0 29 1

91.5oE Measat 1 0 65 1

90.0oE Yamal 201 0 45 0

Orbital Slot Name

Usability

(Degree) HD TV TV Digital TV Analog

87.5oE ChinaStar 1 0 19 0

85.2oE Intelsat 709 0 2 0

83.0oE Insat 2E 0 84 0

83.0oE Insat 3B 0 84 0

80.0oE Express 6A 0 29 1

80.0oE Express AM 2 0 29 1

78.5oE Thaicom 2 0 176 4

78.5oE Thaicom 3 0 176 4

76.5oE Telstar 10 0 169 0

75.0oE LMI 1 0 28 1

74.0oE Insat 3C 0 27 0

74.0oE Edusat 0 1 0

72.0oE PAS 4 N/A N/A N/A

70.5oE Eutelsat W5 1 11 0

Source: http://www.lyngsat.com/nee5.html, Retrieved 20th October, 2010

2.2.2 Birth of Thai Communication Satellites

The national communication satellite is an important asset of all nations for the benefits of both domestic and international telecommunication. In Thailand, His Majesty King Bhumibol Adulyadej of Thailand graciously named the first national communications satellite, “THAICOM” (used as abbreviation) which stands for “Thai Communications”. This name signifies the linkage between “Thailand” and “Communications” [11]

THAICOMs have been launched five communication satellites in a geostationary orbit for use to transmit signal in different purposes such as broadcasting and broadband. THAICOM 1A, 2, 5 are used for TV and radio broadcasting, but THAICOM 4 (or called IPSTAR) is used for broadband such as internet, telephone, VoIP, etc. THAICOM 5’s prime orbital slot is at 78.5 °E, which is the highest penetration for South Asia, Europe, Indochina and Australia. Its strategic orbital slot carries more than 200 national, regional, ethic and global TV channels.

Thaicom Public Company Limited (formerly named Shin Satellite) was founded on 7th November 1991 by Shin Corporation Plc. (“SHIN”), which was granted a 30-year Build-Transfer-Operate concession from Thailand’s Ministry of Transport and Communications (now transferred to “Ministry of Information and Communication Technology”) to operate the country’s first communications satellite, and the concession expires in 2021. The company also certified by ISO 9001-2000 to guarantee customers a world-class product and services.

Specification of THAICOM satellite televisions

Table 2.2: THAICOM 1A, 2, 5 Specifications

http://www.thaicom.net/eng/images/satellite/Thaicom3.jpghttp://www.thaicom.net/eng/images/satellite/pic_Thaicom1A_2.jpghttp://www.thaicom.net/eng/images/satellite/pic_Thaicom1A_2.jpg

THAICOM 2

THAICOM 5

THAICOM 1A

Design

Two identical Hughes HS-376, dual spin stabilized spacecraft

Spacebus 3000A, a three-axis stabilized spacecraft

Manufacturer

Boeing Company, USA

Alcatel Alenia Space, France

Power System

800 Watts at the end

At least 5,000 Watts at the end

Launch Weight

1080 Kg.

Approximately 2,766 Kg.

Mass in Orbit

629 Kg. at the beginning of spacecraft’s life, 450 Kg. At the end.

At least 1,600 Kg. at the beginning of spacecraft’s life, 1,220 Kg. at the end

Life Expectancy

15 years.

At least 12 years

Transponder Capacity

C-band = 12 transponders

KU-band = 3 transponders each, total = 6 @ 54 MHz

C-band = 10

KU-band = 3 transponders each, total = 6 @ 54 MHz

C-band: 25 transponders (all with 36 MHz)

KU-band: 14 transponders (two with 54 MHz and 12 with 36 MHz)

Satellite Location

120 degrees East

78.5 degrees East.

78.5 degrees East

Launch Agency

Ariane 4,Arianespace of France.

Ariane 4, Arianespace of France.

Ariane 5ECA, Arianespace of France

Launch Date

December 17, 1993

October 7, 1994

May 27, 2006

Relocation Date

THAICOM-1A: May-June, 1997

Source: THAICOM Products and Services, http://www.thaicom.net, Retrieved 15th November, 2010

2.2.3 Satellite television transmission and reception system in Thailand

Refer to the part 2.1.4 the configuration of a satellite communications system describes the concept of the satellite communications between ground segment and space segment. In the meantime, this part is to understand space radiocommunications services, frequencies, and angle of azimuth and elevation to know the signal transmission and reception system for Thai satellite television.

In the process of uplink and downlink of data in satellite television between the earth station and communication satellites need to consider the compatibility of frequencies and space radiocommunications services – defined as transmission and reception of radio waves for specific telecommunication applications. [12]

There are many sorts of space radiocommunication services such as Fixed Satellite Service (FSS), Broadcasting Satellite Service (BSS), Mobile Satellite Service (MSS), Earth Exploration Satellite Service (EES), and Space Research Service (SRS), but for satellite television uses FSS and BSS services. FSS is the oldest and most used of all of the satellite services. It is intended for communication through one satellite between earth stations that are fixed, or which are within a specified area. BSS consists of three services specifically designed to provide audio and video entertainment, possibly along with ancillary services, directly to end users; BSS-TV, BSSS-HDTV, and BSS-Sound. BSS is often called Direct Broadcast Satellite (DBS), which similar term is Direct- to-Home (DTH) (Chartrand, 2004)

The FSS and BSS satellite services have major frequencies allocation in C-band and KU-band, which used for satellite television.

Type of frequencies allocations

Frequency (GHz) for uplink/downlink

Band

Space Radiocommunications service

1.6/1.5

MSS

2/2.2

FSS & BSS

6/4

FSS

8/7

Military

14/12-11

FSS & BSS

30/20

FSS

Table 2.3: Frequency allocations

Source: Satellite Communications Systems, 4th edition, 2002

Angle of azimuth and elevation of different areas

Table 2.4 shows the angle of azimuth and elevation in Fixed Satellite Services (FSS) of THAICOM to enable to receive signal from communication satellites that relay on geostationary orbit, which are different depend on specific located area of satellite dish.

Table 2.4: Angle of azimuth and elevation for THAICOM 2/5, C-Band satellite dish

Provinces

Azimuth

Elevation

1.Bangkok

240

2.Krabi

249

3.Kanchanaburi

237

4.Kalasin

239

5.Kamphaeng Phet

233

6.Khon Kaen

238

7.Chanthaburi

244

8.Chachoengsao

241

9.Chon Buri

240

10.Chai Nat

236

11.Chaiyaphum

238

12.Chumphon

244

13.Chiang Rai

229

14.Chiang Mai

229

15.Trang

251

16.Trad

244

17.Tak

233

18.Nakhon Nayok

239

19.Nakhon Pathom

239

20.Nakhon Phanom

238

21.Nakhon Ratchasima

240

22.Nakhon Sri

249

23.Nakhon Sawan

236

24.Nonthaburi

239

25.Narathiwat

255

26.Nan

232

27.Nong Khai

236

28.Buri Ram

241

29.Prathum Thani

239

30.Prachuap Khiri Khan

237

31.Prachin Buri

240

32.Pattani

255

33.Ayutthaya

240

34.Phayao

230

35.Phang Nga

248

36.Phatthalung

252

37.Phichit

235

38.Phitsanulok

234

Provinces

Azimuth

Elevation

39.Phetchaburi

239

40.Phetchabun

236

41.Phrae

232

42.Phuket

249

43.Maha Sarakham

239

44.Mae Hong Son

226

45.Mukdahan

240

46.Yala

255

47.Yasothon

241

48.Roi Et

239

49.Ranong

245

50.Rayong

242

51.Ratchaburi

239

52.Lop Buri

237

53.Lampang

230

54.Lamphun

229

55.Loei

235

56.Si Sa Ket

241

57.Sakon Nakhon

238

58.Songkhla

253

59.Satun

254

60.Samut Prakan

240

61.Samut Songkhram

240

62.Samut Sakhon

240

63.Sa Kaeo

241

64.Saraburi

238

65.Sing Buri

238

66.Sukhothat

232

67.Suphan Buri

238

68.Surat Thani

247

69.Surin

241

70.Nong Bua Lamphu

236

71.Ang Thong

238

72.Amnat Charoen

240

73.Udon Thani

236

74.Uttaradit

232

75.Uthai Thani

236

76.Ubon Ratchathani

242

Source: THAISAT Website, http://www.thaisat.co.th/thaibestmanualb.pdf, Retrieved 15th November 2010

2.3 Satellite dish

2.3.1 Type of satellite dish [13]

There are two types of satellite dish that generally uses for satellite television are KU-band and C-band. KU-band signal has potential to cover in specific and narrow area – Thailand and surrounding area. However, it has very strong signal, so small size of satellite dish (2-5 inch of diameter) can receive signal effectively. Another signal is C-band; this signal covers in a very broad area across continents. As it has a wider beam, the weaker signal it obtained. Thus, C-band uses a bigger size of satellite dish (5-10 inch of diameter) to receive better signal from many satellites, meanwhile many more international channels are available direct to home of viewers.