SATELLITE-COMMUNICATION SYSTEMS

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Cachet: Satellite with scientist.

Info card

SATELLITE-COMMUNICATION SYSTEMS INTELSAT, of which South Africa is a member, is an international consor- tium of 87 countries. INTELSAT is responsible for the provision and opera- tion of the space segment of the global satellite system, which consists of synchronous satellites orbiting in the same direction as the earth in a circular equitorial orbit at an altitude of 36 000 km and completing one orbit in 24 hours therefore appearing stationary above the earth. Three satellites, respectively located above the Atlantic, the Indian and the Pacific oceans, are capable of providing global coverage except over the polar regions. INTELSAT IV-A, which was launched on 25 September 1975, and to which the South African earth station at Hartebeesthoek near Pretoria has access, is capable of providing about 5 000 telephone channels. Earth stations consist of steerable parabolic antennae with a diameter of about 32 m. These antennae lock onto the beacon signals from the satellite and follow the slow drift of the satellite with an accuracy of about one hundredth of a degree. The signals carrying the circuits to all planned destinations in the coverage area are transmitted in a narrow beam by an antenna with a power gain of about two million and are received by the satellite where they are frequency translated, amplified and retransmitted to earth where they are received by the appropriate earth stations. The South African earth station with its two anntenae systems is favourably located in the coverage areas of the Atlantic and Indian ocean systems which can provide service to the Americas, Africa and Europe (via both systems) and to the East, and will supplement the rapidly filling submarine cable to Europe and provide TV relay facilities. SATELLIETKOMMUNIKASIESTELSELS INTELSAT, waarvan Suid-Afrika 'n lid is, is 'n internasionale konsortium van 87 lande. INTELSAT is verantwoordelik vir die voorsiening en werking van die ruimtedeel van die wêreldsatellietstelsel wat bestaan uit sinchrone satel- liete wat in dieselfde rigting as die aarde in 'n sirkelvormige ewenaarsbaan op 'n hoogte van 36 000 km wentel en een omwenteling in 24 uur voltooi sodat dit lyk asof die satelliet staties bo die aarde hang. Drie satelliete, een elk bo die Atlantiese, Indiese en Stille oseaan, kan, met uitsondering van die poolstreke, wêreldwye dekking voorsien. INTELSAT IV-A, wat op 25 September 1975 gelanseer is en waartoe die Suid-Afrikaanse grondstasie op Hartebeesthoek naby Pretoria toegang het, kan ongeveer 5 000 telefoonkanale voorsien. Grondstasies bestaan uit stuurbare paraboolantennes met 'n diameter van ongeveer 32 m. Hierdie antennes sluit op bakenseine van die satelliet af en volg die stadige dwaling van die satelliet met 'n akkuraatheid van ongeveer 'n honderdste van 'n graad. Die seine wat die verbindings na al die beplande bestemmings binne die dekkingsgebied dra, word deur 'n antenne met 'n kragwins van sowat twee miljoen in 'n smal bundel gesend en deur die satelliet ontvang waar dit frekwensie-omgesit, versterk en weer na die aarde gesend word, waar dit dan deur die toepaslike grondstasies ontvang word. Die Suid-Afrikaanse grondstasie, met sy twee antennestelselsis gunstig binne die bereik van die Atlantiese- en Indiese-oseaan-stelsel geleë wat diens kan verskaf na die Amerikas, Afrika en Europa (via albei stelsels) en na die Ooste en sal die onderseekabel na Europa aanvul waarvan die vermoë vinnig opgeneem word. Dit sal ook TV-heruitsendingsfasiliteite voorsien.

Additional information

This cover was postmarked on 3 December 1975 at Pretoria and catalogued as SAPO 2.11. Its cachet featured a satellite alongside a scientist, marking South Africa's membership in INTELSAT, the international satellite consortium that then counted 87 member countries. The cover referenced the newly launched INTELSAT IV-A satellite, connected via South Africa's earth station at Hartebeesthoek near Pretoria, which was capable of carrying around 5000 telephone channels at the time.

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