3 49 - Telenor

1 Guest editorialOdd Gutteberg3 Elements of satellite technologyand communicationOdd Gutteberg4 Satellite communicationsstandardisation in EuropeGunnar Stette22A review of Norwegian space activitiesGeorg Rosenberg26 TSAT - a low-cost satellite communicationnetworkTerje Pettersen and Petter Chr Amundsen31 Very Small Aperture Terminal (VSAT) systems- basic principles and designLiv Oddrun Voll and Gunn Kristin Klungs yr39 Fleet management using INMARSAT-C andGPS - a Norwegian pilot projectArvid Bertheau Johannessen46 Terminals for mobile satellite communicationsJens Anden s49 Future systems for mobile satellitecommunicationsPer Hovstad and Odd Gutteberg54 Effects of atmosphere on earth -space radiopropagationOdd Gutteberg63 The use of millimetre waves insatellite communicationsTord Fredriksen71 The effect of interference for an OBP systemutilising the geostationary orbitPer Hovstad75 earth station antenna technologyArnfinn Nyseth and Svein A Skyttemyr85 ContentsDeveloping the Norwegiantelecommunication network hasalways been a challenging is due to this country s spe-cial topography and its scatteredpopulation.

2 Furthermore, it hasbeen difficult to establish reliablecommunications with the mer-chant fleet, oil rigs, and animportant Norwegian outpost -the Arctic islands of Svalbard(Spitzbergen).In the early sixties, it becameevident that communications viasatellites opened up new oppor-tunities for surmounting thesedifficulties. Norwegian Telecomunderstood the possibilities, andas the first country in Europe,Norway established in 1976 adomestic satellite communica-tion system. This system, calledNORSAT-A, utilised leasedtransponder capacity on the geo-stationary intelsat -IV satel-lite for communication between the Norwegian mainland andthe oil rigs in the North Sea. In 1979 Svalbard was connected tothis system. The earth station at Svalbard was the first commer-cial earth station world-wide, operating with an elevation angleless than 3 success with the NORSAT-A system has been followed upby a meshed network, the NORSAT-B system.

3 This systemutilises Very Small Aperture Terminals (VSAT) for a large shipping nation, Norway caught an early interest inusing satellites for maritime communications. In the seventiesNorwegian Telecom was one of the driving forces behind theestablishement of the International Maritime Satellite Organisa-tion (INMARSAT), and Norway is at present the third largestshareholder. The first European coastal earth station in theINMARSAT system was built in southern Norway, and put intoservice in Norwegian telecommunica-tions industry has been veryactive since satellite transmis-sion was introduced in other things they aremanufacturing the earth stationsin NORSAT-B, and coastalearth stations and mobile termi-nals for the differentINMARSAT standards . Norwe-gian industry has also developeda new data collection satellitesystem, called TSAT (Teleme-try via SATellite).

4 The last addition to the familytree is satellite application is especiallyattractive for a sparsely popu-lated country like Norway. Amajor step was taken when theNorwegian Telecom bought thepowerful TV satellite MarcoPolo 2 from Britain in satellite was renamed Thor and moved to the posi-tion 1 degree west in the geostationary orbit. The purchase ofthis satellite represents a significant change in Norwegian spaceactivity. The Norwegian Telecom has now moved from being asatellite user to a satellite owner and operator - with all the chal-lenging tasks this the satellite technology improves, the earth terminalbecomes smaller and cheaper, as we have seen in the VSAT systems. However, the major challenge for the satellite commu-nity is now to provide a global mobile telephone system withhand-held terminals. This will necessitate studies of new con-cepts such as satellites in low- earth orbits, inter-satellite links,multibeam antennas, on-board processing and possibly use ofhigher frequency editorialBY ODD GUTTEBERG4 Elements of satellite technology and communicationBY ODD GUTTEBERG1 Introduction andoverviewMore than 35 years ago, on 4 October1957, the world s first artificial satellitewas launched by the Soviet Union.

5 Thesatellite, which became known as Sput-nik-I, opened up a new era of practicaluse of the outer space. The satellite sweight was 84 kg and it circled 1400times around the earth before burning upin the atmosphere after 93 days. Thelaunch of Sputnik-I was followed by theUnited States Explorer-I in January1958. Even though these satellites wereprimarily not intended for communica-tions, they demonstrated that this wastechnically and economically use of artificial satellites in earthorbits is now a well established and inte-grated part of the world s telecommuni-cations network. The evolution of thesatellite technology together with morepowerful launchers have made the satel-lites suitable, not only for long distancecommunications, but also for nationalcommunications, television broadcastingand mobile satellite communication system isdivided into two major parts, the earthsegment and the space segment.

6 Thesatellite and its control station form thespace segment, while the earth segmentcomprises the traffic and traffic controlstations, see figure satellite control station (TT&C sta-tion) maintains the satellite in orbit. Itkeeps control of the satellite status(Telemetry), orbital information (Track-ing), and performs orbital attitudemanoeuvres and configures the commu-nication system (Command).The communication part of the satellitesystem is simply a radio system withonly one relay station , the satellite. Thesignals are transmitted on a carrier fre-quency, fA, from an earth station (trafficstation), received in the satellite, ampli-fied, shifted in frequency to f'Aand trans-mitted back to the receiving traffic sta-tion. The satellite transmits and receiveson radio frequencies mainly in themicrowave band, 3 - 30 GHz. Onthese frequencies it is feasible to useparabolic reflector antennas.

7 Such anten-nas concentrate the radio signals in asmall cone; thus it is possible to illumi-nate the whole earth or part of the earth ,see figure 2. The illuminated part iscalled the coverage area, and most of thetransmitted power from the satellite isconcentrated in this area. The larger thetransmitting satellite antenna is, thesmaller the coverage area up-link signals have only one desti-nation, the orbiting satellite, whichmeans that it is required to transmitenergy only to the satellite. The transmit-ting earth station therefore normally con-sists of a large antenna and a high poweramplifier. Since it is expensive and com-plicated to generate an equally highpower in the satellite, the output powerfrom the satellite is generally muchsmaller. Due to this, the receiving earthstations have to use larger receivingantennas; up to 30 metres in diameter, inthe early days of satellite , due to larger satellites, output power, and to better receiv-ing technology, the earth stations can usesmaller and cheaper antennas, satel-lite TV A brief historical reviewThe first person to suggest the use of thegeostationary orbit for communicationsatellites, was the English physicistArthur C Clark (born 1917).

8 He pub-lished his article Extra-TerrestrialRelays in the Wireless World Magazinein October 1945. In this article a satellitesystem for broadcasting of television,was described. At that time there was adiscussion going on about how to dis-tribute television. The present technologywas not mature for the construction ofreliable and unmanned satellites. In 1945no-one could predict the rapid develop-ment within electronics, the inven-tion of the transistor in ASatellite controlstation (TT & C)Trafficstation Bup-linkdown-linkfAf BfBf AFigure 1 The main building blocks in a two-way satellite com-munication systemFigure 2 A geostationary satellite illuminating the coveragearea on Space Age started with the laun-ching of the first artificial satellite,Sputnik-I, in 1957. It is worth whilenoticing that the first trans-Atlantictelephone cable was stretched thesame year.

9 In the following years seve-ral satellites were launched, both forscientific purposes and for other speci-fic applications. Communication expe-riments with passive reflecting satel-lites, Echo-I and -II (1960), were alsocarried operational system with passivesatellites was never realised, but theproject made essential contributions tothe development of the earth first active telecommunicationsatellites were launched in the early1960s, Courier (1960), Telstar-I and -II(1962 and 1963) and Relay-I and -II(1962 and 1964).They were all put into low earth orbits,the height varying between 1,000 and8,000 km. Telstar-I was the mostimportant of these satellites, figure satellite transmitted televisiondirectly from USA to England andFrance for the first time. The Nordiccountries started early to make use ofsatellite communication.

10 In 1964 theNordic countries built a commonreceive earth station at R , outsideGothenburg. It was an experimentalearth station which participated inNASA s experiments with the first satellite in the geostationaryorbit was Syncom-II in 1963. Thelaunch of Syncom-I the same year wasa failure. This was an important break-through for commercial satellite com-munication. Several important experi-ments were carried out. One of themLaunch dataDate:Vehicle:10 July 1962 Thor-DeltaOrbital dataOrbit:Inclination:Apogee:Perigee: degrees5653 km936 minSatellite dataWeight:Diameter:No of transponders:Bandwidth:Output power:77 kg0,9 meter (spherical)150 MHz3 WattsFigure 3 The Telstar satellite, main satellite was designed and built by BellTelephone Laboratories and launched by NASAINTELSAT I(Early Bird)1965240401 intelsat II1967240853 intelsat III19681 2001505 intelsat IV + IVA19716 0007907 + 5 intelsat V198012 0001 04013 intelsat VI198936 0002 2306 intelsat VII199318 0001 40012 TelephonechannelsWeight inorbit (kg)No.