The Pursuit of Equality:The Role of the Ionosphere and Satellite Communicationsin Canadian DevelopmentB.C. Blevis

Bert Blevis, 1974CRC photo 70-30770-01

IntroductionCanada is a vast country. It spans six time zones, and much of the area is dominated by rugged terrain and inhospitable climates. As a result, large stretches of the country are sparsely populated. Most of the population is concentrated in a thin strip along the U. S. border, and even that is clustered heavily in the most southerly portion of the country extending from Windsor, Ontario in the west to Montreal, Qubec in the east. Until the advent of satellite communications, the great rural and remote expanses of the country lacked access to telecommunications and other services taken for granted in the southern urban areas. Well before satellites arrived on the scene, however, Canadian researchers vigorously pursued other avenues of communications to bring the nation together through the enhancement of long distance communications.Early Ionospheric StudiesCanada's early interest in the ionosphere stemmed from two sources (Table I). One was to understand the phenomena which give rise to the beautiful displays of auroral borealis (the northern lights) so often visible over Canada. The aurora borealis is especially prevalent during certain parts of the solar cycle and at particular times of the year. The other source was the attempt to understand the vagaries of the ionosphere -- particularly the causes of disturbances and blackouts experienced in short-wave radio propagation.Indeed, the early moon radar work carried out in Canada in the late 50s was not so much to look at the Moon as a means of communication, or even to explore its surface. Rather it was to use the Moon as a reflecting (or, more correctly, scattering) object beyond the ionosphere to study the effects of the Earth's ionospheric layers on electromagnetic radiation passing through them, including the Faraday rotation of the plane of polarization. The historic message from U. S. President Dwight D. Eisenhower to Canadian Prime Minister John Diefenbaker to commemorate the opening of the Prince Albert Radar Laboratory on June 6, 1959 was transmitted via the Moon. Canadian ionospheric concerns during the 1950s also extended to the problems of using radar to detect any missiles that might pass over the country's polar region.This early attention to the Moon, as well as contemporary studies of reflections from meteor trails, led to a predilection to consider passive satellites, particularly for secure communications. Other passive communications were investigated, including large reflecting balloons such as Echo, clouds of dipoles placed into the Earths orbit (Lincoln Laboratory's Project West Ford), and various proposals for multi-faceted satellites.When Sputnik 1 was launched on 4 October 1957, scientists at Canadas Defence Research Telecommunications Establishment (DRTE) were among the first to monitor its transmissions and determine its orbit. In July 1958, the Space Science Board of the U. S. National Academy of Sciences solicited proposals for scientific experiments to be conducted with satellites, Canadian scientists were eager to participate. On the last day of 1958, the Defence Research Telecommunications Establishment submitted a formal proposal to the then newly-formed National Aeronautics and Space Administration (NASA) for a topside sounding satellite. NASA accepted the proposal in principle on 11 March 1959, and the project (known as Alouette 1) became a joint undertaking between Canada and the U. S. through a letter of agreement between NASA and the Defence Research Board on 16 December 1959.With the launch of Alouette 1 on September 29, 1962 (just before midnight Vandenberg Air Force Base local time on 28 September) Canada became the third country in space after the Soviet Union and the United States. The stage was now set for the unfolding of Canada's space program. However, the government's decision not to develop satellite launch facilities in Canada restricted the space program to projects achievable only through international arrangements with foreign space agencies, such as NASA and the European Space Agency.The principal experiment on the Alouette spacecraft was the ionospheric topside sounder with its two rigid dipole antennas which extended twenty-three meters and forty-five meters tip to tip, respectively. Other experiments included the measurement of cosmic radio noise, very-low-frequency radio emissions, and energetic charged particles.Within a short time after the successful launch of Alouette 1, Canada initiated negotiations with NASA for additional scientific satellites. On 23 May 1963, those negotiations led to the creation of the International Satellites for Ionospheric Studies (ISIS) program consisting of Alouette 2, ISIS 1 and ISIS 2. Alouette 2 (launched 29 November 1965) was a modified version of Alouette 1 and included a probe experiment and an expanded sounder frequency range. The two ISIS spacecraft (launched 30 January 1969 and 31 March 1971, respectively) incorporated additional equipment furnished by the United States.An international working group, called the Topside Sounder Working Group (but later named the ISIS Working Group) was set up in 1960 to provide guidance to the program. In addition to the United States and Canada, Australia, Britain, Finland, France, India, Japan and Norway became involved in the program.Before Alouette 1, scientists had virtually no direct knowledge of the ionosphere above approximately 300 kilometers. The Alouette satellite instruments provided information on electron distributions, their temporal and spatial variations, their irregularities and resonances, the influence of incoming charged particles, cosmic and solar noise, polar cap absorption, solar wind penetration, and ion species in the Earth's atmosphere.The two Alouette and two ISIS satellites were extremely complex spacecraft for their time. They set records for longevity and established a precedent for a long history of international cooperation in space. Alouette 1 was designed to have a lifetime of one year. In private, project scientists hoped to gain at least a month of data from Alouette 1, but in reality the satellite continued to provide data for more than ten years. The ISIS satellites remained operational for about 20 years. In 1987, Alouette 1 was as one of the 10 greatest engineering achievements in Canada in the past century; in 1993, the Institute of Electrical and Electronic Engineers designated the Alouette/ISIS program an International Milestone of Electrical Engineering. Scientists from ten nations published approximately 700 scholarly papers that described the results of the Alouette/ISIS program. This was perhaps the most prolific of any such program.A fourth satellite in the ISIS program (ISIS C) was to have been launched under the agreement with the United States, but it was abandoned in 1969. Canadian space policy had been undergoing some fundamental changes in the previous years. In 1963, for example, the Canadian government decided that the technology that had been resident in the Defence Research Telecommunications Establishment until then was to be transferred to industry during the ISIS program as a means of augmenting the Canadian industrial space capability. Then came a February 1967 government report (the so-called Chapman report) which recommended redirecting space technology research to specific applications -- in particular communications and remote sensing. The objective was to place elements of space technology vital to Canada under Canadian control, as well as to foster a Canadian space industrial capability to meet Canadian needs and to address export markets.A Global FirstEven armed with all the new knowledge about the ionosphere, the emergent communications satellite technology offered the only practical solution for providing reliable telecommunications particularly radio and television, to the 20 percent of Canadians who had no possibility of sharing in the communications and information revolution. To achieve the Canadian Government's priority objective of providing basic telecommunications services to all, Telesat Canada, initially half owned by government and half by the private sector, was created on 1 September 1969.The launch of Anik A in November 1972, and the inauguration of service in 1973, placed Canada in the forefront -- the first country in the world to implement a domestic commercial geostationary satellite system. To complete the initial system, two other Anik A satellites were launched, one in April 1973 and the other in May 1975. Similar to other communications satellite systems of the time, all three Anik A satellites operated at C-band. The Anik B satellite, launched 15 December 1978, was intended to provide Telesat Canada with capacity as a backup for the Anik A series.HermesAfter a long series of discussions, the Canadian Department of Communications and NASA signed an agreement on 20 April 1971 to undertake a joint program called the Communications Technology Satellite (CTS). The CTS was to replace the fourth satellite originally planned as part of the ISIS program. However, because of the number of technological challenges which had to be overcome, the CTS program was not without its detractors. Nonetheless, the Canadian government agreed to take the lead and undertake the development work at its Communications Research Centre. This centre originally had been the Defence Research Telecommunications Establishment; it was transferred to the Department of Communications in August 1969 and renamed.The objective of the program was to advance the state of the art of satellite communications by developing a system capable of operating at higher powers and higher frequencies than existing systems. Such a system would make direct communications possible with low-cost (at the time) ground stations in individual homes and communities. The program also aspired to develop and flight-test a three-axis stabilization system to maintain accurate antenna pointing, and to conduct communications and technological experiments using the system. An additional objective of the CTS program was to improve Canadian industrial capability in the design and manufacture of spacecraft and satellite subsystems. The prevailing political environment influenced the communications experiments, focusing on an evaluation of the economic, social and political impact of new services in the future. Those services included the provision of medical and educational two-way services to remote areas, community interaction, the delivery of government services and direct television broadcasting.Canada designed, built and operated the spacecraft. The United States provided the high-power traveling-wave tube for the satellite transponder, as well as test and launch services for the spacecraft and the launch vehicle. It is interesting to note that the original Canadian proposal included a supplementary L-band mobile satellite communications payload. That payload was dropped in favour of the higher frequency twelve- and fourteen gigahertz package when it was determined that the launch vehicle provided by the United States precluded the inclusion of both systems.Canada and the United States shared the use of the satellite equally. Subsequently, in May 1972, the European Space Research Organization (now the European Space Agency) also participated in the CTS program. The Europeans agreed to provide several components for use in future European communications satellites, including a twenty-watt traveling-wave transmitting tube, in return for developing the solar arrays at no cost to Canada.The CTS, launched on 17 January 17 by a Delta 2916 three-stage rocket was renamed Hermes in Canada when service began on 21 May 1976. The name was chosen from classical Greek mythology. Hermes, the son of Zeus, was considered to be the god of science and invention, as well as of eloquence and dreams. The inauguration of service included a one-hour colour television teleconference between NASAs Lewis Research Center in Cleveland, Ohio, and the Communications Research Centre in Ottawa, Ontario. The Hermes spacecraft was the most powerful civilian spacecraft (as measured by isotropically radiated power) yet launched. Designed to endure two years in space, Hermes operated for almost four years before it was lost.During those four years, the satellite fulfilled all of its objectives. Hermes performed various experiments that proved its usefulness in providing medical and educational services to remote areas (telemedicine and tele-education), in promoting community interaction, in delivering government services, and in demonstrating direct-to-home television using very small reflector antennas. It is believed that the first ever direct-to-home satellite television broadcast was that of a Canadian hockey game in May 1978. The broadcast was transmitted via the Hermes satellite to a sixty-centimetre dish antenna set up at the home of a Canadian embassy official in Lima, Peru during a reception for an international meeting. In August 1979, Hermes, repositioned over the Pacific Ocean, served in a joint satellite communications workshop with Australia and in a demonstration of direct-television broadcasting in Papua New Guinea. It was shortly after this time that control of the satellite was lost and all communications ceased.Nonetheless, for Hermes accomplishments in the field of television broadcasting and its applications, the Communications Research Centre and NASA received EMMY awards from the National Academy of Television Arts and Sciences in 1987. Because of the need to have some back-up and follow-on capability for Hermes in the event of failure of any one of the many innovative subsystems, the Canadian government arranged with Telesat Canada in late 1978 to include fourteen-gigahertz uplink/twelve-gigahertz downlink transponders on its Anik B satellite. As a result, Anik B, launched on Dec. 15, 1978, was the first satellite in the world to operate in both the C-band and the Ku-band.Mobile Satellite CommunicationsAs early as 1967, Canadian researchers had been involved in trials with the United States on the use of ultra-high-frequency (UHF) satellites for mobile services primarily for defence operations. The use of UHF frequencies, with satellites such as LES-5, LES-6 and TACSAT offered the possibility of small lightweight mobile or transportable terminals. Several demonstrations were carried out in land, maritime, and aeronautical environments. The world's first direct aircraft-to-aircraft voice communications via satellite took place on 16 May 1970 between two Canadian Department of National Defence aircraft.The Canadian Department of National Defence continued to use U. S. satellites; Canada never implemented a military UHF mobile satellite system. Nonetheless, the early Canadian efforts led to a proposal, although never implemented, to include a UHF transponder on the Hermes spacecraft. The idea of a Department of National Defence MUSAT (Mobile UHF Satellite) eventually resulted in a proposal for a civilian mobile communications satellite called MSAT. Ultimately, with the encouragement of the Canadian government, and in cooperation with NASA, Telesat Canada and several American companies (which later formed the American Mobile Satellite Company) undertook the development of two satellites to provide mobile satellite services on a commercial basis in North America. Later, the responsibility for Canada's involvement in the project was transferred to a private firm, TMI Communications.ConclusionThe rest of Canada's satellite communications program is more recent history. Canada was one of the founding nations of the satellite-aided search and rescue system known as COSPAS/SARSAT, for Cosmicheskaya Sistemya Poiska Avariynych Sudov (Space System for Search of Distressed Vessels in Russian) and Search and Rescue Satellite-Aided Tracking, which became an almost instant success after the launch of the first spacecraft in 1982. Researchers at the Communications Research Centre participated in the European Space Agency's large, high-powered, multi-purpose Olympus communications satellite. These researchers continue to make a major contribution to the development of new communications technologies, to carry out studies on the next generation of satellite communications systems, and to explore new ways of providing access by all Canadians to the new multimedia information superhighway.Telesat (now a private company with no government ownership) has gone on to launch its Ku-band Anik C, C-band Anik D, and the hybrid Anik E series of satellites. Anik E made history when both satellites failed during a unusual solar event, but were subsequently recovered by Telesat to full operation. The early mobile satellite communications activities at the Communications Research Centre have led to the manufacture of American Mobile Satellite Corporation's AMSC-1 satellite that was launched earlier in 1995, and of MSAT-1, launched on 20 April 1996 and placed in geostationary orbit at 107. 5 degrees West.Teleglobe, Canada's international telecommunications carrier, is a signatory to, and a major player in, Intelsat and Inmarsat. It has become a partner in the Orbcomm Little LEO (low-Earth orbit) satellite and now is participating with TRW in the Big LEO satellite program called Odyssey.Canada, spurred on by necessity of providing for the social, economic and political needs of a population widely dispersed over a vast, and sometimes inhospitable, terrain and subject to a harsh climate, played a major role in the exploration of the ionosphere and in the early international development of satellite communications. It has maintained its leading role through succeeding generations of new satellites, and technological progress, and can be expected to remain at the forefront of satellite communications technology well into the future.

Chronology of Canada's Early Ionospheric and Communications Satellite Programs:1839First magnetic observatory established at University of Toronto

1882-83First International Polar Year; measurements of magnetic and auroral phenomena

Dec. 12, 1901Marconi's Transatlantic transmission to Signal Hill, NF

1932-33Second IPY; field stations established in north; eclipse measurements

1941Ionosonde installed north of Ottawa by National Research Council

1947Formation of Canadian Defence Research Board (DRB); continuing ionospheric studies at DRB's Telecommunications Establishment

Oct. 4, 1957Sputnik 1 First artificial earth satellite (U.S.S.R.), IGY

Jan. 1958Explorer 1 First American satellite (Discovery of Van Allen belts)

July 1958Satellite proposals invited by Space Science Board of U.S. NAS

Dec. 31, 1958Canadian proposal submitted for top-side sounding satellite

Mar. 11, 1959NASA approval in principle for top-side sounder

June 6, 1959Lunar communications demo at opening of Prince Albert Radar Laboratory

Dec. 16, 1959Letter of Agreement between NASA and DRB for Alouette

1960Echo I

Sept. 29, 1962Alouette I Canadian topside sounder; first satellite by other than U.S.S.R. or U.S.A.

1962Telstar I First transatlantic television via satellite

May 23, 1963ISIS Program Canada/U.S. MOU for joint program to launch 4 additional satellites

Aug. 1963Agreement with NASA for Canadian participation in testing of experimental communications satellites, including commitment to build a ground station

Apr. 6, 1965Early Bird First international commercial communications satellite

Nov. 29, 1965Alouette II

Feb. 1967Recommendation that prime Canadian objective in space technology be its applications to domestic telecommunications and resource survey

Jan. 30, 1969ISIS I

Aug. 1969Formation of Department of Communications

Sept. 1, 1969Establishment of Telesat Canada

May 16, 1970First aircraft-to-aircraft voice transmission using LES-6

1970CTS program begins

Mar. 31, 1971ISIS II

Nov. 1972Anik A1 First domestic commercial geostationary communications satellite

Apr. 1973Anik A2

May 1975Anik A3

Jan. 17, 1976CTS/Hermes First high-powered, Ku-band satellite, world's most powerful to date

Dec. 15, 1978Anik B First commercial hybrid (C and Ku-band) satellite

Sept. 1987EMMY Award to NASA and DOC for Hermes contribution to broadcasting

The Pursuit of Equality:Peran Ionosfer dan Satelit KomunikasiPembangunan KanadaBC BlevisBert Blevis 1974CRC foto 70-30770-01

PengantarKanada adalah negara yang sangat luas.Ini mencakup enam zona waktu, dan sebagian besar wilayah didominasi oleh medan kasar dan tidak ramah iklim.Akibatnya, membentang besar negara yang jarang penduduknya.Sebagian besar penduduk terkonsentrasi di strip tipis di sepanjang perbatasan AS, dan bahkan yang berkerumun berat di bagian paling selatan negara membentang dari Windsor, Ontario di barat ke Montreal, Quebec di timur.Sampai munculnya komunikasi satelit, hamparan pedesaan dan terpencil besar negara tidak memiliki akses telekomunikasi dan layanan lainnya diambil untuk diberikan di daerah perkotaan selatan.Nah sebelum satelit tiba di tempat kejadian, namun, peneliti Kanada penuh semangat dikejar cara lain komunikasi untuk membawa bangsa bersama-sama melalui peningkatan komunikasi jarak jauh.Studi ionosfer AwalMinat awal Kanada di ionosfer berasal dari dua sumber (Tabel I).Salah satunya adalah untuk memahami fenomena yang menimbulkan menampilkan indah borealis aurora (cahaya utara) begitu sering terlihat di atas Kanada.Aurora borealis sangat lazim selama bagian-bagian tertentu dari siklus matahari dan pada waktu tertentu tahun.Sumber lainnya adalah upaya untuk memahami liku-liku ionosfer - terutama penyebab gangguan dan pemadaman berpengalaman dalam radio gelombang pendek propagation.Indeed, bulan awal kerja radar yang dilakukan di Kanada pada akhir 50-an tidak begitu banyak untuk melihat bulan sebagai sarana komunikasi, atau bahkan untuk menjelajahi permukaannya.Sebaliknya itu menggunakan Bulan sebagai refleksi (atau, lebih tepatnya, hamburan) objek luar ionosfer untuk mempelajari efek dari lapisan ionosfer Bumi pada radiasi elektromagnetik melewati mereka, termasuk rotasi Faraday dari bidang polarisasi.Pesan bersejarah dari Presiden AS Dwight D. Eisenhower ke Perdana Menteri Kanada John Diefenbaker untuk memperingati pembukaan Laboratorium Radar Pangeran Albert pada tanggal 6 Juni 1959 ditularkan melalui Bulan.Kekhawatiran ionosfer Kanada selama tahun 1950 juga meluas ke masalah menggunakan radar untuk mendeteksi rudal yang mungkin melewati daerah kutub negara.Perhatian awal ke Bulan, serta studi kontemporer refleksi dari jalur meteor, menyebabkan kecenderungan untuk mempertimbangkan satelit pasif, terutama untuk komunikasi yang aman.Komunikasi pasif lainnya diselidiki, termasuk balon besar yang mencerminkan seperti Echo, awan dipol ditempatkan ke orbit bumi (Lincoln Laboratory Project Barat Ford), dan berbagai proposal untuk satelit multi-faceted.Ketika Sputnik 1 diluncurkan pada 4 Oktober 1957, para ilmuwan di Kanada Pertahanan Penelitian Telekomunikasi Pendirian (DRTE) adalah di antara yang pertama untuk memantau transmisi dan menentukan orbitnya.Pada bulan Juli 1958, Ilmu Dewan Ruang Nasional Academy of Sciences AS diminta proposal untuk percobaan ilmiah yang akan dilakukan dengan satelit, para ilmuwan Kanada sangat ingin berpartisipasi.Pada hari terakhir tahun 1958, Research Pertahanan Telekomunikasi Pendirian mengajukan proposal resmi kepada National Aeronautics and Space Administration kemudian baru terbentuk (NASA) untuk satelit topside terdengar.NASA menerima usulan secara prinsip pada 11 Maret 1959, dan proyek (dikenal sebagai Alouette 1) menjadi suatu usaha bersama antara Kanada dan Amerika Serikat melalui surat perjanjian antara NASA dan Badan Penelitian Pertahanan pada 16 Desember 1959.Dengan peluncuran Alouette 1 pada September 29, 1962 (tepat sebelum tengah malam Vandenberg Air Force Base waktu setempat pada tanggal 28 September) Kanada menjadi negara ketiga di ruang setelah Uni Soviet dan Amerika Serikat.Panggung sekarang ditetapkan untuk terungkapnya program ruang angkasa Kanada.Namun, keputusan pemerintah untuk tidak membangun fasilitas peluncuran satelit di Kanada membatasi program ruang untuk proyek dicapai hanya melalui pengaturan internasional dengan badan ruang angkasa asing, seperti NASA dan European Space Agency.Percobaan utama pada pesawat ruang angkasa Alouette adalah sounder topside ionosfer dengan dua antena dipol yang kaku yang diperpanjang dua puluh tiga meter dan empat puluh lima meter ujung ke ujung, masing-masing.Percobaan lain termasuk pengukuran kosmik suara radio, emisi radio frekuensi sangat rendah, dan partikel bermuatan energik.Dalam waktu singkat setelah sukses peluncuran Alouette 1, Kanada memulai negosiasi dengan NASA untuk satelit ilmiah tambahan.Pada tanggal 23 Mei tahun 1963, negosiasi yang menyebabkan penciptaan dari Satelit Internasional untuk Studi ionosfer (ISIS) Program terdiri dari Alouette 2, ISIS 1 dan 2. ISIS Alouette 2 (diluncurkan 29 November 1965) adalah versi modifikasi dari Alouette 1 dan termasuk probe percobaan dan rentang frekuensi sehat diperluas.Dua pesawat ruang angkasa ISIS (diluncurkan 30 Januari 1969 dan 31 Maret 1971, masing-masing) dimasukkan peralatan tambahan dilengkapi oleh Amerika Serikat.Sebuah kelompok kerja internasional, yang disebut Kelompok Kerja Sounder Topside (tetapi kemudian bernama Kelompok Kerja ISIS) didirikan pada tahun 1960 untuk memberikan bimbingan kepada program.Selain Amerika Serikat dan Kanada, Australia, Inggris, Finlandia, Perancis, India, Jepang dan Norwegia menjadi terlibat dalam program ini.Sebelum Alouette 1, para ilmuwan telah hampir tidak ada pengetahuan langsung dari ionosfer di atas sekitar 300 kilometer.Instrumen satelit Alouette yang memberikan informasi tentang distribusi elektron, variasi temporal dan spasial mereka, penyimpangan dan resonansi, pengaruh partikel bermuatan yang masuk, kosmik dan solar kebisingan, penyerapan topi kutub, penetrasi angin matahari, dan spesies ion di atmosfer bumi.Kedua Alouette dan dua satelit ISIS adalah pesawat ruang angkasa yang sangat kompleks untuk waktu mereka.Mereka mencetak rekor untuk umur panjang dan membentuk preseden untuk sejarah panjang kerja sama internasional dalam ruang.Alouette 1 dirancang untuk memiliki seumur hidup satu tahun.Secara pribadi, ilmuwan proyek berharap untuk mendapatkan setidaknya satu bulan data dari Alouette 1, tetapi dalam kenyataannya satelit terus menyediakan data untuk lebih dari sepuluh tahun.ISIS satelit tetap beroperasi selama sekitar 20 tahun.Pada tahun 1987, Alouette 1 adalah sebagai salah satu dari 10 medali rekayasa terbesar di Kanada di abad yang lalu;pada tahun 1993, Institute of Electrical dan Electronic Engineers ditunjuk program Alouette / ISIS sebuah Internasional Milestone Teknik Elektro.Para ilmuwan dari sepuluh negara yang diterbitkan sekitar 700 makalah ilmiah yang menggambarkan hasil dari program Alouette / ISIS.Ini mungkin yang paling produktif dari program tersebut.Sebuah satelit keempat dalam program ISIS (ISIS C) adalah telah diluncurkan di bawah perjanjian dengan Amerika Serikat, tapi itu ditinggalkan pada tahun 1969. kebijakan ruang Kanada telah mengalami beberapa perubahan mendasar dalam tahun-tahun sebelumnya.Pada tahun 1963, misalnya, pemerintah Kanada memutuskan bahwa teknologi yang telah penduduk di Pertahanan Penelitian Telekomunikasi Pendirian sampai saat itu akan ditransfer ke industri selama program ISIS sebagai sarana menambah kemampuan ruang industri Kanada.Kemudian datang seorang Februari 1967 laporan pemerintah (yang disebut laporan Chapman) yang direkomendasikan mengarahkan penelitian teknologi ruang untuk aplikasi tertentu - dalam komunikasi tertentu dan penginderaan jauh.Tujuannya adalah untuk menempatkan unsur-unsur teknologi ruang penting untuk Kanada di bawah kendali Kanada, serta untuk mendorong kemampuan industri ruang Kanada untuk memenuhi kebutuhan Kanada dan untuk mengatasi pasar ekspor.Global PertamaBahkan dipersenjatai dengan semua pengetahuan baru tentang ionosfer, teknologi satelit komunikasi muncul menawarkan satu-satunya solusi praktis untuk menyediakan telekomunikasi yang handal - terutama radio dan televisi, dengan 20 persen dari Kanada yang tidak memiliki kemungkinan berbagi dalam revolusi komunikasi dan informasi.Untuk mencapai tujuan prioritas Pemerintah Kanada menyediakan layanan telekomunikasi dasar untuk semua, Telesat Canada, awalnya setengah dimiliki oleh pemerintah dan setengah oleh sektor swasta, diciptakan pada 1 September 1969.Peluncuran Anik A pada November 1972, dan peresmian layanan pada tahun 1973, menempatkan Kanada di garis depan - negara pertama di dunia yang menerapkan sistem satelit geostasioner komersial domestik.Untuk melengkapi sistem awal, dua satelit Anik A lainnya diluncurkan, satu pada bulan April 1973 dan yang lainnya di Mei 1975. Serupa dengan sistem satelit komunikasi lain waktu, ketiga Anik A satelit dioperasikan pada C-band.The Anik B satelit yang diluncurkan 15 Desember 1978, dimaksudkan untuk memberikan Telesat Kanada dengan kapasitas sebagai cadangan untuk Anik seri A.HermesSetelah serangkaian panjang diskusi, Departemen Komunikasi Kanada dan NASA menandatangani perjanjian pada 20 April 1971 untuk melakukan program bersama yang disebut Teknologi Komunikasi Satelit (CTS).The CTS adalah untuk menggantikan satelit keempat awalnya direncanakan sebagai bagian dari program ISIS.Namun, karena sejumlah tantangan teknologi yang harus diatasi, program CTS bukan tanpa pengkritiknya.Meskipun demikian, pemerintah Kanada setuju untuk memimpin dan melakukan pekerjaan pembangunan di perusahaan Communications Research Centre.Pusat ini awalnya merupakan Penelitian Pertahanan Telekomunikasi Pendirian;itu dipindahkan ke Departemen Perhubungan pada bulan Agustus 1969 dan berganti nama.Tujuan dari program ini adalah untuk memajukan keadaan seni komunikasi satelit dengan mengembangkan sistem yang mampu beroperasi pada kekuatan yang lebih tinggi dan frekuensi yang lebih tinggi daripada sistem yang ada.Sistem seperti ini akan membuat komunikasi langsung mungkin dengan biaya rendah (pada saat itu) stasiun bumi di rumah dan masing-masing komunitas.Program ini juga bercita-cita untuk mengembangkan dan penerbangan-menguji sistem stabilisasi tiga sumbu untuk menjaga antena menunjuk akurat, dan untuk melakukan komunikasi dan eksperimen teknologi menggunakan sistem.Sebuah Tujuan tambahan dari program CTS adalah untuk meningkatkan kemampuan industri Kanada dalam desain dan pembuatan pesawat antariksa dan satelit subsistem.Yang berlaku lingkungan politik mempengaruhi percobaan komunikasi, dengan fokus pada evaluasi dampak ekonomi, sosial dan politik dari layanan baru di masa depan.Layanan tersebut meliputi penyediaan layanan dua arah medis dan pendidikan untuk daerah-daerah terpencil, interaksi masyarakat, penyampaian layanan pemerintah dan siaran televisi langsung.Kanada dirancang, dibangun dan dioperasikan pesawat ruang angkasa.Amerika Serikat memberikan daya tinggi perjalanan gelombang tabung untuk transponder satelit, serta layanan pengujian dan peluncuran pesawat ruang angkasa dan peluncuran kendaraan.Sangat menarik untuk dicatat bahwa usulan Kanada asli termasuk tambahan L-band komunikasi satelit mobile payload.Payload yang dijatuhkan mendukung dua belas frekuensi yang lebih tinggi dan empat belas paket gigahertz saat dipastikan bahwa kendaraan peluncuran yang disediakan oleh Amerika Serikat menghalangi masuknya kedua sistem.Kanada dan Amerika Serikat berbagi penggunaan satelit sama.Selanjutnya, pada bulan Mei tahun 1972, Space Research Organization Eropa (sekarang Badan Antariksa Eropa) juga berpartisipasi dalam program CTS.Orang-orang Eropa setuju untuk menyediakan beberapa komponen untuk digunakan di masa depan satelit komunikasi Eropa, termasuk dua puluh watt perjalanan gelombang transmisi tabung, sebagai imbalan untuk mengembangkan array surya tanpa biaya ke Kanada.The CTS, diluncurkan pada 17 Januari 17 oleh Delta 2916 tiga tahap roket berganti nama Hermes di Kanada ketika layanan dimulai pada tanggal 21 Mei 1976. Nama itu dipilih dari mitologi Yunani klasik.Hermes, putra Zeus, yang dianggap sebagai dewa ilmu pengetahuan dan penemuan, serta kefasihan dan impian.Peresmian layanan termasuk warna teleconference televisi satu jam antara Lewis Research Center NASA di Cleveland, Ohio, dan Komunikasi Research Centre di Ottawa, Ontario.Hermes pesawat ruang angkasa adalah pesawat ruang angkasa sipil yang paling kuat (yang diukur dengan kekuatan isotropically memancarkan) belum diluncurkan.Dirancang untuk bertahan dua tahun di ruang angkasa, Hermes beroperasi selama hampir empat tahun sebelum itu hilang.Selama empat tahun, satelit memenuhi semua tujuannya.Hermes melakukan berbagai eksperimen yang terbukti kegunaannya dalam memberikan pelayanan medis dan pendidikan di daerah terpencil ("telemedicine" dan "tele-education"), dalam mempromosikan interaksi masyarakat, dalam memberikan pelayanan pemerintah, dan dalam menunjukkan televisi direct-to-rumah menggunakan sangat antena reflektor kecil.Hal ini diyakini bahwa pertama siaran televisi satelit pernah direct-to-rumah adalah bahwa dari permainan hoki Kanada Mei 1978. siaran itu ditransmisikan melalui satelit Hermes untuk antena parabola enam puluh sentimeter didirikan di rumah seorang kedutaan Kanada resmi di Lima, Peru pada resepsi untuk pertemuan internasional.Pada bulan Agustus 1979, Hermes, reposisi di atas Samudera Pasifik, disajikan dalam lokakarya komunikasi satelit bersama dengan Australia dan demonstrasi siaran langsung televisi di Papua Nugini.Itu tak lama setelah waktu ini yang mengontrol satelit hilang dan semua komunikasi berhenti.Meskipun demikian, untuk Hermes prestasi di bidang penyiaran televisi dan aplikasinya, Komunikasi Pusat Penelitian dan NASA menerima penghargaan EMMY dari National Academy of Television Arts and Sciences pada tahun 1987. Karena kebutuhan untuk memiliki beberapa back-up dan tindak-on Kemampuan untuk Hermes dalam hal kegagalan salah satu dari banyak subsistem inovatif, pemerintah Kanada diatur dengan Telesat Kanada pada akhir tahun 1978 untuk memasukkan empat belas-gigahertz transponder uplink / downlink dua belas-gigahertz satelit Anik B-nya.Akibatnya, Anik B, diluncurkan pada 15 Desember 1978, merupakan satelit pertama di dunia yang beroperasi di kedua C-band dan Ku-band.Mobile Communications SatelitPada awal tahun 1967, peneliti Kanada telah terlibat dalam uji coba dengan Amerika Serikat pada penggunaan frekuensi ultra-tinggi (UHF) satelit untuk layanan mobile terutama untuk operasi pertahanan.Penggunaan frekuensi UHF, dengan satelit seperti LES-5, LES-6 dan TacSat menawarkan kemungkinan terminal mobile atau diangkut kecil ringan.Beberapa demonstrasi dilakukan di tanah, maritim, dan lingkungan aeronautika.Pertama komunikasi dunia langsung pesawat-ke-pesawat suara melalui satelit berlangsung pada 16 Mei 1970 antara dua Canadian Departemen pesawat Pertahanan Nasional.The Canadian Departemen Pertahanan Nasional terus menggunakan satelit AS;Kanada tidak pernah menerapkan sistem satelit bergerak UHF militer.Meskipun demikian, awal upaya Kanada menyebabkan proposal, meskipun tidak pernah dilaksanakan, untuk menyertakan transponder UHF pada pesawat ruang angkasa Hermes.Ide dari Departemen Pertahanan Musat Nasional (Mobile Satellite UHF) akhirnya menghasilkan proposal untuk satelit komunikasi mobile sipil disebut MSAT.Pada akhirnya, dengan dorongan dari pemerintah Kanada, dan bekerja sama dengan NASA, Telesat Kanada dan beberapa perusahaan Amerika (yang kemudian membentuk Amerika Mobile Satellite Company) melakukan pengembangan dua satelit untuk menyediakan layanan satelit mobile secara komersial di Amerika Utara .Kemudian, tanggung jawab untuk keterlibatan Kanada dalam proyek dipindahkan ke sebuah perusahaan swasta, TMI Communications.KesimpulanSisa program komunikasi satelit Kanada adalah sejarah yang lebih baru.Kanada adalah salah satu negara pendiri pencarian dan penyelamatan sistem satelit-dibantu dikenal sebagai COSPAS / SARSAT, untuk Cosmicheskaya Sistemya Poiska Avariynych Sudov (Space Sistem Cari Kapal Tertekan di Rusia) dan Search and Rescue Satellite-Aided Tracking, yang menjadi sukses hampir instan setelah peluncuran pesawat ruang angkasa pertama pada tahun 1982. Para peneliti di Pusat Penelitian Komunikasi berpartisipasi dalam besar, bertenaga tinggi, multi-tujuan Olympus komunikasi satelit Badan Antariksa Eropa.Para peneliti ini terus memberikan kontribusi besar terhadap perkembangan teknologi komunikasi baru, untuk melakukan penelitian pada generasi berikutnya dari sistem komunikasi satelit, dan untuk mengeksplorasi cara-cara baru untuk menyediakan akses bagi semua Kanada untuk informasi multimedia superhighway baru.Telesat (sekarang sebuah perusahaan swasta tanpa kepemilikan pemerintah) telah pergi untuk meluncurkan Ku-band Anik C, C-band Anik D, dan E series hybrid Anik satelit.Anik E membuat sejarah ketika kedua satelit gagal selama acara solar biasa, tetapi kemudian ditemukan oleh Telesat untuk beroperasi penuh.Awal kegiatan komunikasi satelit bergerak di Komunikasi Pusat Penelitian telah menyebabkan pembuatan Amerika Mobile Satellite Corporation AMSC-1 satelit yang diluncurkan sebelumnya pada tahun 1995, dan MSAT-1, diluncurkan pada tanggal 20 April 1996 dan ditempatkan di orbit geostasioner pada 107 . 5 derajat Barat.Teleglobe, operator telekomunikasi internasional Kanada, adalah penandatangan, dan pemain utama dalam, Intelsat dan Inmarsat.Hal ini telah menjadi mitra dalam Orbcomm kecil LEO (orbit rendah Bumi) satelit dan sekarang berpartisipasi dengan TRW dalam program satelit Big LEO disebut Odyssey.Kanada, didorong oleh perlunya menyediakan kebutuhan sosial, ekonomi dan politik populasi tersebar luas di atas luas, dan kadang-kadang tidak ramah, medan dan tunduk pada iklim yang keras, memainkan peran utama dalam eksplorasi ionosfer dan dalam pembangunan internasional awal komunikasi satelit.Ini telah mempertahankan peran utama melalui generasi penerus dari satelit baru, dan kemajuan teknologi, dan dapat diharapkan untuk tetap berada di garis depan teknologi komunikasi satelit baik ke masa depan.

Kronologi Kanada Awal ionosfir dan Komunikasi Program Satelit:1839Observatorium magnetik pertama didirikan di University of Toronto

1882-1883Pertama International Polar Year;pengukuran fenomena magnetik dan aurora

12 Desember 1901Transmisi Transatlantic Marconi untuk Signal Hill, NF

1932-1933IPY kedua;stasiun lapangan yang didirikan di bagian utara;pengukuran gerhana

1941Ionosonde diinstal utara dari Ottawa oleh Dewan Riset Nasional

1947Pembentukan Kanada Badan Penelitian Pertahanan (DRB);melanjutkan studi ionosfer di DRB yang Telekomunikasi Pendirian

4 Oktober 1957Sputnik 1 Pertama satelit bumi buatan (USSR), IgY

Januari 1958Explorer 1 satelit pertama Amerika (Penemuan sabuk Van Allen)

Juli 1958Proposal satelit diundang oleh Space Science Dewan US NAS

31 Desember 1958Proposal Kanada diajukan untuk top-side terdengar satelit

11 Maret 1959Persetujuan NASA pada prinsipnya untuk top-side sehat

6 Juni 1959Komunikasi Lunar demo di pembukaan Laboratorium Radar Prince Albert

16 Desember 1959Surat Perjanjian antara NASA dan DRB untuk Alouette

1960Echo I

29 Sep 1962Alouette I Canadian sounder topside;satelit pertama dengan selain Uni Soviet atau Amerika Serikat

1962Telstar I Pertama televisi transatlantik melalui satelit

23 Mei 1963ISIS Program Canada / US MOU untuk program bersama untuk meluncurkan 4 satelit tambahan

Agustus 1963Perjanjian dengan NASA untuk partisipasi Kanada dalam pengujian eksperimental satelit komunikasi, termasuk komitmen untuk membangun stasiun tanah

6 April 1965Awal satelit komunikasi komersial internasional Bird Pertama

29 Nov 1965Alouette II

Februari 1967Rekomendasi bahwa tujuan utama di Kanada teknologi ruang angkasa menjadi aplikasi untuk telekomunikasi dalam negeri dan survei sumber daya

30 Januari 1969ISIS Saya

Agustus 1969Pembentukan Departemen Perhubungan

1 September 1969Pembentukan Telesat Canada

16 Mei 1970Transmisi suara pesawat-ke-pesawat pertama menggunakan LES-6

1970Program CTS dimulai

31 Maret 1971ISIS II

November 1972Anik A1 Pertama geostasioner satelit komunikasi komersial domestik

April 1973Anik A2

Mei 1975Anik A3

17 Januari 1976CTS / Hermes Pertama bertenaga tinggi, satelit Ku-band, dunia yang paling kuat sampai saat ini

15 Desember 1978Anik B Pertama hibrida komersial (C dan Ku-band) satelit

September 1987EMMY Award kepada NASA dan DOC atas kontribusi Hermes untuk penyiaran

http://www.friendsofcrc.ca/Articles/Blevis-Pursuit%20of%20Equality/BertBlevis.html

Satellite positioning influenced by the ionosphereThe ionosphere of the Earth constantly varies, depending on the time of day, the season, the geographical position, and the level of solar activity. This area of the atmosphere consists of several conductive layers that reflect radio waves, a characteristic which is of interest for scientists and engineers, especially in the telecommunications industry.The condition of the ionosphere affects the quality oftraditional radio communication. In our space era of satellites, we may wonder whether this ancient way of communicating and the study of the ionosphere are still current topics.The answer is definitely yes! The ionosphere, for instance, (strongly) affects the signals that satellites communicate.Positioning system Galileo. Credits ESA.Understanding and predicting the turbulent regions of the ionosphere and their effects onsatellite communicationshas important applications for military operations in remote locations, planned networks of mobile communications satellites, high-precision applications of global navigation satellite systems (U.S.GPS, RussianGLONASSand EuropeanGalileo), and many others.

Only imagine what the consequences would be, if the data from such a positioning system was badly affected by the evolution in the ionospheres condition and was not corrected.Therefore it is vital that we continuously track the ionized layers in our upper atmosphere.

Posisi satelit dipengaruhi oleh ionosferIonosfer Bumi terus bervariasi, tergantung pada waktu hari, musim, posisi geografis, dan tingkat aktivitas matahari.Daerah ini atmosfer terdiri dari beberapa lapisan konduktif yang mencerminkan gelombang radio, karakteristik yang menarik bagi para ilmuwan dan insinyur, terutama di industri telekomunikasi.Kondisi ionosfer mempengaruhi kualitaskomunikasi radio tradisional.Dalam era ruang kita satelit, kita mungkin bertanya-tanya apakah cara ini kuno berkomunikasi dan studi ionosfer masih "topik saat ini".Jawabannya pasti ya!Ionosfer, misalnya, (sangat) mempengaruhi sinyal bahwa satelit berkomunikasi.Positioning system Galileo.Kredit ESA.Memahami dan memprediksi daerah bergolak ionosfer dan pengaruhnya terhadapkomunikasi satelitmemiliki aplikasi penting untuk operasi militer di daerah terpencil, jaringan direncanakan mobile satelit komunikasi, aplikasi presisi tinggi dari sistem satelit navigasi global (USGPS, GLONASSRusia dan EropaGalileo), dan banyak lainnya.

Hanya membayangkan apa konsekuensinya akan, jika data dari suatu sistem positioning yang sangat terpengaruh oleh evolusi dalam kondisi ionosfer dan tidak diperbaiki.Oleh karena itu sangat penting bahwa kami terus melacak lapisan terionisasi di atmosfer atas kami.

http://www.aeronomie.be/en/topics/earthsystem/ionosphere-gps.htm

http://lasp.colorado.edu/media/education/reu/2007/docs/talks/fuller_rowell_ionosphere.pdf

Issue 55 / July - September 2006

The Importance of Ionosphere in Radio CommunicationBy Mehmet Camalan

The first step in using electromagnetic waves in space for radio communication was taken by James Clark Maxwell when he came up with the theory of the electromagnetic field in 1873. Maxwell claimed that magnetic waves were subject to reflection, refraction, and absorption, just as light is. The existence of these waves was first demonstrated by Heinrich Rudolph Hertz in some experiments carried out in 1888. His studies constituted the base for Guglielmo Marconi to conduct experiments with wireless telegraphy using Morse code.

In 1896, Marconi was successful in sending signals through a wireless telegraph to a distance of a few kilometers away. However, how would it be possible to provide intercontinental communication via radiotelegraphy and radiotelephone? In 1901, together with his assistants, G.S. Kemp and P.W. Paget, Marconi successfully transmitted and received transatlantic signals between Poldhu, Cornwall and New Foundland, Canada, using a kite aerial at Signal Hill in Cornwall, England. It was Edward Appleton who first discovered that radio waves were broadcast around the world after they are reflected back from the ionosphere, one of the highest electrified layers of the atmosphere that contains large concentrations of charged particles (ions) and free electrons. Electromagnetic waves that are sent from radio transmitters to outer space are reflected back to every corner of the Earth after hitting this gas and plasma layer that is composed of charged particles. Thus, radio and radiotelephone communication is made possible for the benefit of human beings. After that time, being able to use a law that had been ordained by the Supreme Creator, human beings were able to reach a level that enabled them to conduct transatlantic communications via radiotelegraphy. But what makes radio waves so special?

Radio wavesThe frequency spectrum of electromagnetic waves begins from the sub-sound frequency region (1Hz) stretching up until cosmic rays (Figure 1). Radio communication is made using the electromagnetic waves that form part of this frequency spectrum. Radio communication systems can be classified into four groups relating to their frequency regions:

- LF/MF (Low Frequency/Medium Frequency)- HF (High Frequency)- VHF/UHF (Very /Ultra High Frequency)- SHF (Super High Frequency)

Specifications of radio waves are taken into account in this classification. The main element that makes radio waves similar or different from each other is the frequency band that determines their wave length. Radio waves move at the speed of light (300 thousand km per second), much faster than sound itself, so to find the wave length of a radio wave, we divide its velocity by its frequency.

Frequencies used within the radio frequency spectrum measure between 20 KHz and 30 GHz. Theoretically, the high frequency band is between 3 and 30 MHz, while in practice it is between 1.6 and 30 MHz. The interval between 4 and 18 MHz is the most-widely used region in the spectrum.

The atmosphereOur Lord, Who incessantly prepares the Earth in a beautiful manner, also protects all of life with a perfect shield called the atmosphere. Scientists have divided the atmosphere into seven layers in order to reveal the unknown facts about it. These seven layers are different from each other in terms of temperature, pressure and humidity levels, and the natural events that occur in them. If we ascend from the Earth toward the sky, we pass through the layers of the troposphere, stratosphere, ozonosphere, mesosphere, thermosphere, ionosphere and the exosphere. All these layers cover a distance of about 3,000 km. Each of the atmospheric layers serves a vital cause. Every layer has many functions, ranging from the formation of rain clouds to the prevention of harmful beams reaching the Earth, from reflecting radio waves to inactivating meteors. One duty of the ionosphere that we are aware of today is to act as a reflector and distributor for radio waves.

The ionosphere and distribution of radio wavesGood transatlantic radio communication depends upon many factors. Depending on the frequency of the radio waves, the season of the year, the position of the Sun, the location of the broadcasting area and the time of day, the communication area may vary from 100 km to 10,000 km.

Radio waves are propagated around the Earth in two forms, either as ground waves or as sky waves (Figure 2). In high-frequency radio communication, it is important to choose the best frequency for the time and means of propagation.

Starting from 50 km above the Earth and stretching 440 km, the ionosphere is filled with a high concentration of free electrons and gases. Why is the ionosphere important for transatlantic radio communication? The electrified ions that fill the whole of the ionospheric layer that completely surrounds the Earth reflect radio waves from all directions to every part of the world. According to their frequencies and ionization, radio waves are completely absorbed in the ionosphere and they are either partly refracted and distributed to the outer space or are reflected and returned to the world. The electromagnetic waves within a range of 30 MHz can return to Earth after being reflected by the ionosphere.

It is accepted that the ionosphere is formed at different ionizing levels in different layers, known as D, E, F1, and F2 (Figure 3). The ionization level in the outer layers of the ionosphere is higher than that of the inner layers. The D layer, the innermost layer of the ionosphere, is 76-93 km above the Earth and is characterized by low ion densities and low collision frequencies of electrons and ions with neutral particles. Serving to absorb most energy below 7 MHz, this layer is ionized during the daylight hours, completely disappearing at night. It reaches full ionization level just after sunrise and is at its peak at noon time, immediately losing energy after sun-set.

The E layer is the region of the ionosphere that was discovered first. In this layer, molecular ion production is at its peak at about 110-115 km above the Earth. There are plenty of molecular gases at this height. This layer is a suitable platform from which radio operators can reflect signals to distant stations. Reaching a maximum at noon, the ionization in the E layer decreases towards the end of the day, disappearing completely at midnight. Moreover, at unpredictable intervals, ionized gas clouds accumulate in certain regions of this layer. This can be detected by the variable dense clouds of ionization that occur in the E layer due to the spatial and temporal structure in the ionizing particle precipitation. The plasma density of the E layer can be greatly changed because of these occasional formations. These formations, which are called sporadic E layers, are used by radio amateurs for long distance VHF (Very High Frequency) operation. Since the plasma density in layers D and E is highest at noon and present during the other hours of daylight, these layers are used in the daytime.

The next layer of ionosphere exists at about 160 and 400 km above the Earth and consists of layers that have a higher density of free electrons caused by the ionizing effect of solar radiation. Since the density of gas molecules at this height is low, ion and electron collisions occur very slowly in this layer. When solar radiation is high (during the day) this layer can be divided into two independent regions, F1 and F2. The F1 layer is present at 152 and 203 km above the surface of the Earth. During the night, the F1 layer merges with the F2 layer. The F2 layer exists at 250 and 400 km above the surface of the Earth. The majority of HF (shortwave) transmissions are propagated by the F2 layer, which is the main reflecting layer for HF communications both at day and at night. Reaching its maximum level of ionization just after midday, the layer is at its minimum just before sunrise. The F2 layer can be used for 10-20 MHz during the day and 3-8 MHz during the night. Since the F layer exists at a very high altitude, it is exposed to sunlight for longer periods of the day and it dissipates very slowly at night. In this case, the only layer of the ionosphere that can be used during the night is the F layer, which I is composed of the F1 and F2 layers.

Solar radiation, and consequently ionization, alters periodically. For instance, as the days are long during the summer months, ionization is also high at this period. During this time, radio waves are absorbed or attenuated more in layers E and D, and propagation covers only a small area. However, since the days are shorter during the autumn and winter, less solar energy reaches these ionospheric layers. Hence, low frequencies can easily pass through the weakly ionized D and E layers and reach the stronger F layer from where they can be propagated over long distances.

Another long term factor in ionization is the regular 11-year activity cycle of sun spots. Sun spots are believed to be caused by violent eruptions on the Sun and they are characterized by unusually strong magnetic fields. During periods of maximum sun spot activity, the density of ionization increases in all the layers of the ionosphere. During these periods, the D layer absorbs more and the critical frequencies of layers E, F1 and F2 are higher, therefore, for long distance communication higher operating frequencies over 30 MHz should be used. During terms of minimum sun spot activity, the E and F layers have weak ionization, so they cannot reflect the radio waves back onto the Earth. In this period, frequencies over 20 MHz are not used much. Along with this regular variation, sudden ionospheric disturbances (SID) also negatively affect the propagation of radio waves. SID are thought to be caused by severe solar eruptions, but the real cause of this phenomena is still not clearly known. (Figure 4)

Sudden ionospheric disturbances can disturb radio communication for hours or even days. Strong solar eruptions cause a sudden abnormal increase in the ionization density in the D layer, hence even the high frequency radio waves coming from the side of the Earth that is facing the Sun are completely absorbed by this layer and frequencies above 2 MHz are unable to penetrate it. When SID occurs, long distance propagation of HF radio waves may be completely blocked.

Ionospheric storms are another disturbing factor for radio communication. When a solar eruption occurs, it takes between 20 and 40 hours for the magnetic storm to reach the Earth. The ionospheric storms cause the F2 layer to virtually lose its ion density. At this time, when the range of frequencies used for communication is much smaller than normal, communication is only possible at lower frequencies.

Frequency and propagation routes in radio communicationsThe definition of the frequency to be used for radio communication is an important parameter for ensuring healthy propagation. For this, the Maximum Usable Frequency (MUF), and the Lowest Usable Frequency (LUF) are determined. Frequencies over MUF penetrate the ionosphere, shooting right through the ionosphere and going out into space, whereas frequencies below MUF are reflected. LUF is the lowest frequency that is completely absorbed in the D layer. To conduct good communication, a frequency, calculated as MUF0.85, should be used. This frequency may be lower at night and higher during the day.

Apart from the propagation frequency, the path that is chosen to transmit the radio waves from one point to the other also must be calculated accurately. The angle at which the radio waves enter the atmosphere (angle of incidence) defines the path that will be covered by the waves on their way to Earth. The angle of incidence should be small enough for the waves to be reflected back to Earth and large enough so that the waves will not penetrate the ionospheric layer. Smaller critical angles should be used for smaller frequencies and larger critical angles should be used for larger frequencies so that they will not penetrate through the ionospheric layer and be lost in space.

Consequently, apart from periods when solar eruptions are strong, radio waves that are over 30 MHz frequency are not reflected and can penetrate the atmosphere and reach outer space, hence making the communication between outer space and the Earth possible.

For transatlantic communications conducted via communication satellites, radio waves over 30 MHz are used. Artificial satellites imitate the ionospheric layer, their original source of inspiration, and act as a reflector for these waves (Figure 5). Waves coming from the Earth are reflected by these satellites if they are within their coverage area. However, these manmade satellites have very limited coverage areas. Although they are produced with the highest technology available, their cost is very high and they last only for about 25 years. Nevertheless, for radio waves lower than 30 MHz, the ionosphere, that covers the whole of our planet, acts as a natural satellite. Because of this characteristic of the ionosphere, we do not have to focus at any certain point. Moreover, there is no need for maintenance, nor any energy supplement, and the ionosphere is permanent. The atmosphere has been granted for our service for as long as Earth survives. Through searching and exploring new facts about the universe and all beings, we realize more and more that neither meaningless nor useless matter exists in the material world of creation. Therefore, we are better able to understand that the universe is packed with wonderful favors and blessings that are addressed directly to humanity.

Pentingnya Ionosfer Komunikasi RadioMehmet Camalan

Langkah pertama dalam menggunakan gelombang elektromagnetik dalam ruang untuk komunikasi radio diambil oleh James Clark Maxwell ketika ia datang dengan "teori medan elektromagnetik" pada tahun 1873. Maxwell menyatakan bahwa gelombang magnetik tunduk pada refleksi, refraksi, dan penyerapan, hanya seperti terang.Keberadaan gelombang ini pertama kali ditunjukkan oleh Heinrich Hertz Rudolph dalam beberapa percobaan yang dilakukan pada tahun 1888. Studinya merupakan dasar untuk Guglielmo Marconi untuk melakukan eksperimen dengan telegrafi nirkabel menggunakan kode Morse.

Pada tahun 1896, Marconi berhasil mengirimkan sinyal melalui telegraf nirkabel untuk jarak beberapa kilometer jauhnya.Namun, bagaimana mungkin untuk menyediakan komunikasi antar melalui radiotelegraphy dan telepon radio?Pada tahun 1901, bersama dengan asistennya, GS Kemp dan PW Paget, Marconi berhasil dikirim dan diterima sinyal transatlantik antara Poldhu, Cornwall dan New Foundland, Kanada, menggunakan layang-layang udara di Signal Hill di Cornwall, Inggris.Itu Edward Appleton yang pertama kali menemukan bahwa gelombang radio yang disiarkan di seluruh dunia setelah mereka dipantulkan kembali dari ionosfer, salah satu lapisan listrik tertinggi atmosfer yang mengandung konsentrasi besar partikel bermuatan (ion) dan elektron bebas.Gelombang elektromagnetik yang dikirim dari pemancar radio ke angkasa luar yang dipantulkan kembali ke setiap sudut bumi setelah memukul gas dan plasma ini lapisan yang terdiri dari partikel bermuatan.Dengan demikian, radio dan komunikasi telepon radio dimungkinkan untuk kepentingan manusia.Setelah itu, bisa menggunakan undang-undang yang telah ditetapkan oleh Pencipta Agung, manusia mampu mencapai tingkat yang memungkinkan mereka untuk melakukan komunikasi transatlantik melalui radiotelegraphy.Tapi apa yang membuat gelombang radio begitu istimewa?

Gelombang radioSpektrum frekuensi gelombang elektromagnetik dimulai dari "sub-suara daerah frekuensi" (1Hz) peregangan sampai sinar kosmik (Gambar 1).Komunikasi radio dibuat menggunakan gelombang elektromagnetik yang merupakan bagian dari spektrum frekuensi ini.Sistem komunikasi radio dapat diklasifikasikan ke dalam empat kelompok yang berkaitan dengan daerah frekuensi mereka:

- LF / MF (Frekuensi Rendah / Frekuensi Menengah)- HF (High Frequency)- VHF / UHF (Very / Frekuensi Ultra Tinggi)- SHF (Super High Frequency)

Spesifikasi dari gelombang radio yang diperhitungkan dalam klasifikasi ini.Unsur utama yang membuat gelombang radio yang sama atau berbeda satu sama lain adalah band frekuensi yang menentukan panjang gelombang mereka.Gelombang radio bergerak pada kecepatan cahaya (300 ribu km per detik), jauh lebih cepat daripada suara itu sendiri, sehingga untuk menemukan panjang gelombang gelombang radio, kita membagi kecepatannya dengan frekuensi.

Frekuensi yang digunakan dalam spektrum mengukur frekuensi radio antara 20 KHz dan 30 GHz.Secara teoritis, pita frekuensi tinggi antara 3 dan 30 MHz, sementara dalam prakteknya adalah antara 1,6 dan 30 MHz.Interval antara 4 dan 18 MHz adalah wilayah yang paling banyak digunakan dalam spektrum.

SuasanaTuhan kita, yang tak henti-hentinya mempersiapkan Bumi dengan cara yang indah, juga melindungi semua kehidupan dengan perisai sempurna yang disebut "suasana." Para ilmuwan telah membagi atmosfer menjadi tujuh lapisan untuk mengungkapkan fakta-fakta yang tidak diketahui tentang hal itu.Ketujuh lapisan yang berbeda satu sama lain dalam hal tingkat suhu, tekanan dan kelembaban, dan peristiwa alam yang terjadi di dalamnya.Jika kita naik dari bumi ke langit, kita melewati lapisan troposfer, stratosfer, ozonosfir, mesosfer, termosfer, ionosfer dan eksosfer.Semua lapisan ini menempuh jarak sekitar 3.000 km.Setiap lapisan atmosfer menyajikan penyebab penting.Setiap lapisan memiliki banyak fungsi, mulai dari pembentukan awan hujan dengan pencegahan balok berbahaya mencapai bumi, dari mencerminkan gelombang radio untuk menonaktifkan meteor.Salah satu tugas dari ionosfer yang kita menyadari hari ini adalah untuk bertindak sebagai reflektor dan distributor untuk gelombang radio.

Ionosfer dan distribusi gelombang radioBaik transatlantik radio komunikasi tergantung pada banyak faktor.Tergantung pada frekuensi gelombang radio, musim tahun ini, posisi Matahari, lokasi daerah penyiaran dan waktu hari, area komunikasi dapat bervariasi dari 100 km menjadi 10.000 km.

Gelombang radio yang disebarkan di sekitar Bumi dalam dua bentuk, baik sebagai gelombang tanah atau sebagai gelombang langit (Gambar 2).Dalam frekuensi tinggi komunikasi radio, penting untuk memilih frekuensi yang terbaik untuk saat ini dan berarti propagasi.

Mulai dari 50 km di atas Bumi dan peregangan 440 km, ionosfer diisi dengan konsentrasi tinggi elektron bebas dan gas.Mengapa ionosfer penting untuk komunikasi radio transatlantik?Ion yang listrik yang mengisi seluruh lapisan ionosfer yang benar-benar mengelilingi Bumi mencerminkan gelombang radio dari semua arah untuk setiap bagian dari dunia.Menurut frekuensi dan ionisasi mereka, gelombang radio benar-benar diserap di ionosfer dan mereka baik sebagian dibiaskan dan didistribusikan ke luar angkasa atau tercermin dan kembali ke dunia.Gelombang elektromagnetik dalam jarak 30 MHz dapat kembali ke bumi setelah tercermin ionosfer.

Hal ini diterima bahwa ionosfer terbentuk pada tingkat pengion yang berbeda dalam lapisan yang berbeda, yang dikenal sebagai D, E, F1, F2 dan (Gambar 3).Tingkat ionisasi di lapisan luar ionosfer lebih tinggi dibandingkan dengan lapisan dalam.Lapisan D, lapisan terdalam dari ionosfer, adalah 76-93 km di atas Bumi dan ditandai dengan kepadatan ion rendah dan frekuensi tabrakan rendah elektron dan ion dengan partikel netral.Melayani untuk menyerap sebagian besar energi di bawah 7 MHz, lapisan ini terionisasi pada siang hari, benar-benar menghilang di malam hari.Mencapai tingkat ionisasi penuh hanya setelah matahari terbit dan pada puncaknya pada waktu siang hari, segera kehilangan energi setelah matahari-set.

E layer wilayah ionosfer yang ditemukan pertama kali.Dalam lapisan ini, produksi ion molekul pada puncaknya sekitar 110-115 km di atas Bumi.Ada banyak gas molekul pada ketinggian ini.Lapisan ini merupakan platform yang cocok dari mana operator radio dapat mencerminkan sinyal ke stasiun yang jauh.Mencapai maksimum pada siang hari, ionisasi di lapisan E menurun menjelang akhir hari, menghilang sepenuhnya pada tengah malam.Selain itu, pada interval yang tak terduga, awan gas terionisasi menumpuk di daerah tertentu dari lapisan ini.Hal ini dapat dideteksi oleh awan pekat variabel ionisasi yang terjadi di lapisan E karena struktur spasial dan temporal di presipitasi pengion partikel.Kepadatan plasma lapisan E dapat sangat berubah karena formasi sesekali.Formasi tersebut, yang disebut "lapisan E sporadis," digunakan oleh amatir radio VHF untuk jarak jauh (Frekuensi Sangat Tinggi) operasi.Karena kepadatan plasma di lapisan D dan E adalah tertinggi pada siang hari dan hadir selama jam siang hari yang lain, lapisan ini digunakan di siang hari.

Lapisan berikutnya ionosfer ada sekitar 160 dan 400 km di atas Bumi dan terdiri dari lapisan yang memiliki kepadatan yang lebih tinggi dari elektron bebas yang disebabkan oleh efek pengion radiasi matahari.Karena kepadatan molekul gas pada ketinggian ini rendah, ion dan elektron tabrakan terjadi sangat lambat dalam lapisan ini.Ketika radiasi matahari tinggi (siang hari) lapisan ini dapat dibagi menjadi dua wilayah yang independen, F1 dan F2.Lapisan F1 hadir di 152 dan 203 km di atas permukaan bumi.Selama malam, lapisan F1 menyatu dengan lapisan F2.Lapisan F2 ada di 250 dan 400 km di atas permukaan bumi.Mayoritas HF (gelombang pendek) transmisi yang disebarkan oleh lapisan F2, yang merupakan refleksi lapisan utama untuk komunikasi HF baik pada siang dan malam hari.Mencapai tingkat maksimum ionisasi setelah tengah hari, lapisan adalah minimum yang sebelum matahari terbit.Lapisan F2 dapat digunakan untuk 10-20 MHz siang hari dan 3-8 MHz pada malam hari.Karena lapisan F ada pada ketinggian yang sangat tinggi, terkena sinar matahari lebih lama hari dan menghilang sangat lambat di malam hari.Dalam hal ini, satu-satunya lapisan ionosfer yang dapat digunakan pada malam hari adalah lapisan F, yang saya terdiri dari F1 dan F2 lapisan.

Radiasi matahari, dan akibatnya ionisasi, mengubah secara berkala.Misalnya, seperti hari-hari yang panjang selama bulan-bulan musim panas, ionisasi juga tinggi pada periode ini.Selama ini, gelombang radio yang diserap atau dilemahkan lebih dalam lapisan E dan D, dan propagasi hanya mencakup wilayah kecil.Namun, sejak hari lebih pendek selama musim gugur dan musim dingin, kurang energi surya mencapai lapisan-lapisan ionosfer.Oleh karena itu, frekuensi rendah dapat dengan mudah melewati lapisan D dan E lemah terionisasi dan mencapai lapisan kuat F dari mana mereka dapat diperbanyak jarak jauh.

Faktor jangka panjang lain dalam ionisasi adalah 11-tahun siklus aktivitas rutin bintik matahari.Sun bintik diyakini disebabkan oleh letusan kekerasan terhadap Matahari dan mereka ditandai dengan medan magnet luar biasa kuat.Selama periode aktivitas matahari maksimum tempat, kepadatan meningkat ionisasi di semua lapisan ionosfer.Selama periode ini, lapisan D menyerap lebih banyak dan frekuensi kritis lapisan E, F1 dan F2 yang lebih tinggi, oleh karena itu, untuk jarak jauh komunikasi yang lebih tinggi frekuensi operasi lebih dari 30 MHz harus digunakan.Selama hal aktivitas minimum tempat matahari, E dan lapisan F memiliki ionisasi lemah, sehingga mereka tidak dapat mencerminkan gelombang radio kembali ke bumi.Dalam periode ini, frekuensi lebih dari 20 MHz tidak banyak digunakan.Seiring dengan variasi biasa ini, "gangguan ionosfer mendadak (SID)" juga negatif mempengaruhi propagasi gelombang radio.SID diduga disebabkan oleh letusan matahari yang parah, namun sebenarnya penyebab fenomena ini masih belum diketahui secara pasti.(Gambar 4)

Gangguan ionosfer mendadak dapat mengganggu komunikasi radio selama berjam-jam atau bahkan berhari-hari.Letusan matahari yang kuat menyebabkan peningkatan abnormal mendadak kepadatan ionisasi di lapisan D, maka bahkan gelombang radio frekuensi tinggi yang datang dari sisi bumi yang menghadap matahari benar-benar diserap oleh lapisan ini dan frekuensi di atas 2 MHz tidak dapat menembusnya.Ketika SID terjadi, propagasi jarak jauh dari gelombang radio HF dapat benar-benar diblokir.

Badai ionosfer adalah faktor lain yang mengganggu komunikasi radio.Ketika letusan matahari terjadi, dibutuhkan antara 20 dan 40 jam untuk badai magnetik untuk mencapai Bumi.Badai ionosfer menyebabkan lapisan F2 untuk hampir kehilangan kepadatan ion.Pada saat ini, ketika rentang frekuensi yang digunakan untuk komunikasi jauh lebih kecil dari biasanya, komunikasi hanya mungkin pada frekuensi yang lebih rendah.

Rute frekuensi dan propagasi dalam komunikasi radioDefinisi frekuensi yang akan digunakan untuk komunikasi radio merupakan parameter penting untuk memastikan propagasi sehat.Untuk ini, Frekuensi Maksimum Usable (MUF), dan terendah Usable Frequency (LUF) ditentukan.Frekuensi di MUF menembus ionosfer, menembak menembus ionosfer dan pergi ke ruang angkasa, sedangkan frekuensi di bawah MUF tercermin.LUF adalah frekuensi terendah yang benar-benar diserap di lapisan D.Untuk melakukan komunikasi yang baik, frekuensi, dihitung sebagai MUFA-0,85, harus digunakan.Frekuensi ini mungkin lebih rendah pada malam hari dan lebih tinggi pada siang hari.

Selain frekuensi propagasi, jalan yang dipilih untuk mengirimkan gelombang radio dari satu titik ke titik yang lain juga harus dihitung secara akurat.Sudut di mana gelombang radio memasuki atmosfer (sudut insiden) mendefinisikan jalur yang akan dicakup oleh gelombang dalam perjalanan mereka ke Bumi.Sudut datang harus cukup kecil untuk gelombang yang akan dipantulkan kembali ke Bumi dan cukup besar sehingga gelombang tidak akan menembus lapisan ionosfer.Sudut kritis yang lebih kecil harus digunakan untuk frekuensi yang lebih kecil dan sudut kritis yang lebih besar harus digunakan untuk frekuensi yang lebih besar sehingga mereka tidak akan menembus lapisan ionosfer dan akan hilang dalam ruang.

Akibatnya, selain dari periode ketika letusan matahari yang kuat, gelombang radio yang lebih frekuensi 30 MHz tidak tercermin dan dapat menembus atmosfer dan mencapai luar angkasa, sehingga membuat komunikasi antara ruang luar dan Bumi mungkin.

Untuk komunikasi transatlantik dilakukan melalui satelit komunikasi, gelombang radio lebih dari 30 MHz yang digunakan.Satelit buatan meniru lapisan ionosfer, sumber aslinya inspirasi, dan bertindak sebagai reflektor untuk gelombang ini (Gambar 5).Gelombang yang datang dari Bumi tercermin oleh satelit ini jika mereka berada dalam cakupan area mereka.Namun, satelit buatan manusia telah sangat terbatas cakupan wilayah.Meskipun mereka diproduksi dengan teknologi tertinggi yang tersedia, biaya mereka sangat tinggi dan masih ada hanya untuk sekitar 25 tahun.Namun demikian, untuk gelombang radio yang lebih rendah dari 30 MHz, ionosfer, yang mencakup seluruh planet kita, bertindak sebagai satelit alami.Karena karakteristik ini ionosfer, kita tidak harus fokus pada setiap titik tertentu.Selain itu, tidak ada kebutuhan untuk pemeliharaan, atau suplemen energi, dan ionosfer adalah permanen.Atmosfer telah diberikan untuk layanan kami selama bertahan Bumi.Melalui mencari dan mengeksplorasi fakta-fakta baru tentang alam semesta dan semua makhluk, kita menyadari semakin banyak yang peduli tidak berarti tidak berguna ada di dunia materi penciptaan.Oleh karena itu, kita lebih mampu memahami bahwa alam semesta dikemas dengan nikmat yang indah dan berkat yang ditujukan langsung kepada umat manusia.

http://www.fountainmagazine.com/Issue/detail/The-Importance-of-Ionosphere-in-Radio-Communication

The Ionosphere and Radiowave Propagation- an overview or tutorial about the ionosphere, and how it affects radiowave propagation and radio communications.As electromagnetic waves, and in this case, radio signals travel, they interact with objects and the media in which they travel. As they do this the radio signals can be reflected, refracted or diffracted. These interactions cause the radio signals to change direction, and to reach areas which would not be possible if the radio signals travelled in a direct line.The ionosphere is a particularly important region with regards to radio signal propagation and radio communications in general. Its properties govern the ways in which radio communications, particularly in the HF radio communications bands take place.The ionosphere is a region of the upper atmosphere where there are large concentrations of free ions and electrons. While the ions give the ionosphere its name, but it is the free electrons that affect the radio waves and radio communications. In particular the ionosphere is widely known for affecting signals on the short wave radio bands where it "reflects" signals enabling these radio communications signals to be heard over vast distances. Radio stations have long used the properties of the ionosphere to enable them to provide worldwide radio communications coverage. Although today, satellites are widely used, HF radio communications using the ionosphere still plays a major role in providing worldwide radio coverage.The ionosphere extends over more than one of the meteorological areas, encompassing the mesosphere and the thermosphere, it is an area that is characterised by the existence of positive ions (and more importantly for radio signals free electrons) and it is from the existence of the ions that it gains its name.

BasicsThe free electrons do not appear over the whole of the atmosphere. Instead it is found that the number of free electrons starts to rise at altitudes of approximately 30 kilometres. However it is not until altitudes of around 60 to 90 kilometres are reached that the concentration is sufficiently high to start to have a noticeable effect on radio signals and hence on radio communications systems. It is at this level that the ionosphere can be said to start.The ionisation in the ionosphere is caused mainly by radiation from the Sun. In addition to this, the very high temperatures and the low pressure result in the gases in the upper reaches of the atmosphere existing mainly in a monatomic form rather than existing as molecules. At lower altitudes, the gases are in the normal molecular form, but as the altitude increases the monatomic forms are more in abundance, and at altitudes of around 150 kilometres, most of the gases are in a monatomic form. This is very important because it is found that the monatomic forms of the gases are very much easier to ionise than the molecular forms.

IonisationThe Sun emits vast quantities of radiation of all wavelengths and this travels towards the Earth, first reaching the outer areas of the atmosphere. In creating the ionisation it is found that when radiation of sufficient intensity strikes an atom or a molecule, energy may be removed from the radiation and an electron removed, producing a free electron and a positive ion. In the example given below, the simple example of a helium atom is give, although other gases including oxygen and nitrogen are far more common.

Ionisation of molecules by solar radiation

The radiation from the Sun covers a vast spectrum of wavelengths. However in terms of the effect it has on the atoms of molecules it can be considered as photons. The electrons in the atoms or molecules can be considered as orbiting the central nucleus consisting of protons and neutrons. Electrons are tied or bound to their orbit around the nucleus by electro-static forces, the electron is negatively charged and the nucleus is positively charged. There are equal numbers of electrons and protons in any molecule and as a result it is electro-statically neutral.When a photon strikes the atom, or molecule, the photon transfers its energy to the electron as excess kinetic energy. Under some circumstances this excess energy may exceed the binding energy in the atom or molecule and the electron escapes the influence of the positive charge of the nucleus. This leaves a positively charged nucleus or ions and a negatively charged electron, although as there are the same number of positive ions and negative electrons the whole gas still remains with an overall neutral charge.Most of the ionisation in the ionosphere results from ultraviolet light, although this does not mean that other wavelengths do not have some effect. Additionally, each time an atom or molecule is ionised a small amount of energy is used. This means that as the radiation passes further into the atmosphere, its intensity reduces. It is for this reason that the ultraviolet radiation causes most of the ionisation in the upper reaches of the ionosphere, but at lower altitudes the radiation that is able to penetrate further cause more of the ionisation. Accordingly, extreme ultra-violet and X-Rays give rise to most of the ionisation at lower altitudes. This reduction in these forms of radiation protects us on the surface of the Earth from the harmful effects of these rays.The level of ionisation varies over the extent of the ionosphere, being far from constant. One reason is that the level of radiation reduces with decreasing altitude. Also the density of the gases varies. In addition to this there is a variation in the proportions of monatomic and molecular forms of the gases, the monatomic forms of gases being far greater at higher altitudes. These and a variety of other phenomena mean that there are variations in the level of ionisation with altitude.The level of ionisation in the ionosphere also changes with time. It varies with the time of day, time of year, and according to many other external influences. One of the main reasons why the electron density varies is that the Sun, which gives rise to the ionisation is only visible during the day. While the radiation from the Sun causes the atoms and molecules to split into free electrons and positive ions. The reverse effect also occurs. When a negative electron meets a positive ion, the fact that dissimilar charges attract means that they will be pulled towards one another and they may combine. This means that two opposite effects of splitting and recombination are taking place. This is known as a state of dynamic equilibrium. Accordingly the level of ionisation is dependent upon the rate of ionisation and recombination. This has a significant effect on radio communications.

A simplified view of the layers in the ionosphere over the period of a day

Other effects like the season and the state of the Sun also have a major effect. Sunspots and solar disturbances have a major impact on the level of radiation received, and these effects are covered in other articles on this website on Sunspots and Solar Disturbances. The season also has an effect. Again this is covered in other articles on the Radio-Electronics.Com website. However very briefly, the radiation received from the Sun varies in the same way that heat from the Sun varies according to the season, and accordingly the level of ionisation and free electrons changes. However this is a very simplified view as other facts also come into play.

Ionospheric layersThe traditional view of the ionosphere indicates a number of distinct layers, each affecting radio communications in slightly different ways. Indeed, the early discoveries of the ionosphere indicated that a number of layers were present. While this is a convenient way of picturing the structure of the ionosphere it is not exactly correct. Ionisation exists over the whole of the ionosphere, its level varying with altitude. The peaks in level may be considered as the different layers or possibly more correctly, regions. These regions are given letter designations: D, E, and F regions. There is also a C region below the others, but the level of ionisation is so low that it does not have any effect radio signals and radio communications, and it is rarely mentioned.

The typical electron distribution in the ionosphere

The different layers or regions in the ionosphere have different characteristics and affect radio communications in different ways. There are also differences in the exact way they are created and sustained. In view of this it is worth taking a closer look at each one in detail and the way they vary over the complete day during light and darkness.

D RegionThe D region is the lowest of the regions within the ionosphere that affects radio communications signals to any degree. It is present at altitudes between about 60 and 90 kilometres and the radiation within it is only present during the day to an extent that affects radio waves noticeably. It is sustained by the radiation from the Sun and levels of ionisation fall rapidly at dusk when the source of radiation is removed. It mainly has the affect of absorbing or attenuating radio communications signals particularly in the LF and MF portions of the radio spectrum, its affect reducing with frequency. At night it has little effect on most radio communications signals although there is still a sufficient level of ionisation for it to refract VLF signals.The layer is chiefly generated by the action of a form of radiation known as Lyman radiation which has a wavelength of 1215 Angstroms and ionises nitric oxide gas present in the atmosphere. Hard X-Rays also contribute to the ionisation, especially towards the peak of the solar cycle.

E RegionThe region above the D region is the E region. It exists at altitudes between about 100 and 125 kilometres. Instead of attenuating radio communications signals this layer chiefly refracts them, often to a degree where they are returned to earth. As such they appear to have been reflected by this layer. However this layer still acts as an attenuator to a certain degree.Like the D region, the level of ionisation falls relatively quickly after dark as the electrons and ions re-combine and it virtually disappears at night. However the residual night time ionisation in the lower part of the E region causes some attenuation of signals in the lower portions of the HF part of the radio communications spectrum.The ionisation in this region results from a number of types of radiation. Soft X-Rays produce much of the ionisation, although extreme ultra-violet (EUV) rays (very short wavelength ultra-violet light) also contribute. Broadly the radiation that produces ionisation in this region has wavelengths between about 10 and 100 Angstroms. The degree to which all of the constituents contribute depends upon the state of the Sun and the latitude at which the observations are made.

F RegionThe most important region in the ionosphere for long distance HF radio communications is the F region. During the daytime when radiation is being received from the Sun, it often splits into two, the lower one being the F1 region and the higher one, the F2 region. Of these the F1 region is more of an inflection point in the electron density curve (seen above) and it generally only exists in the summer.Typically the F1 layer is found at around an altitude of 300 kilometres with the F2 layer above it at around 400 kilometres. The combined F layer may then be centred around 250 to 300 kilometres. The altitude of the all the layers in the ionosphere layers varies considerably and the F layer varies the most. As a result the figures given should only be taken as a rough guide. Being the highest of the ionospheric regions it is greatly affected by the state of the Sun as well as other factors including the time of day, the year and so forth.The F layer acts as a "reflector" of signals in the HF portion of the radio spectrum enabling world wide radio communications to be established. It is the main region associated with HF signal propagation.Like the D and E layers the level of ionisation of the F region varies over the course of the day, falling at night as the radiation from the Sun disappears. However the level of ionisation remains much higher. The density of the gases is much lower and as a result the recombination of the ions and electrons takes place more slowly, at about a quarter of the rate that it occurs in the E region. As a result of this it still has an affect on radio signals at night being able to return many to Earth, although it has a reduced effect in some aspects.The F region is at the highest region in the ionosphere and as such it experiences the most solar radiation. Much of the ionisation results from ultra-violet light in the middle of the spectrum as well as those portions of the spectrum with very short wavelengths. Typically the radiation that causes the ionisation is between the wavelengths of 100 and 1000 Angstroms, although extreme ultra-violet light is responsible for some ionisation in the lower areas of the F region.

SummaryThe ionosphere is a continually changing area of the atmosphere. Extending from altitudes of around 60 kilometres to more than 400 kilometres it contains ions and free electrons. The free electrons affect the ways in which radio waves propagate in this region and they have a significant effect on HF radio communications.The ionosphere can be categorised into a number of regions corresponding to peaks in the electron density. These regions are named the D, E, and F regions. In view of the fact that the radiation from the Sun is absorbed as it penetrates the atmosphere, different forms of radiation give rise to the ionisation in the different regions as outlined in the summary table below:Summary of forms of radiation causing ionisation in the ionosphere.

REGIONPRIMARY IONISING RADIATION FORMS

CCosmic

DLyman alpha, Hard X-Rays

ESoft X-Rays and some Extreme Ultra-Violet

F1Extreme Ultra-violet, and some Ultra-Violet

F2Ultra-Violet

The ionosphere is a continually changing area. It is obviously affected by radiation from the Sun, and this changes as a result aspects including of the time of day, the geographical area of the world, and the state of the Sun. As a result radio communications using the ionosphere change from one day to the next, and even one hour to the next. Predicting how what radio communications will be possible and radio signals may propagate is of great interest to a variety of radio communications users ranging from broadcasters to radio amateurs and two way radio communications systems users to those with maritime mobile radio communications systems and many more.

The Ionosfer dan Propagasi Gelombang radio- Gambaran atau tutorial tentang ionosfer, dan bagaimana hal itu mempengaruhi gelombang radio propagasi dan komunikasi radio.Sebagai gelombang elektromagnetik, dan dalam hal ini, perjalanan sinyal radio, mereka berinteraksi dengan objek dan media di mana mereka melakukan perjalanan.Ketika mereka melakukan hal ini sinyal radio dapat tercermin, dibiaskan atau difraksi.Interaksi ini menyebabkan sinyal radio untuk mengubah arah, dan untuk menjangkau daerah-daerah yang tidak akan mungkin jika sinyal radio perjalanan di garis langsung.Ionosfer adalah wilayah yang sangat penting berkaitan dengan propagasi sinyal radio dan komunikasi radio pada umumnya.Sifat-sifatnya mengatur cara di mana komunikasi radio, khususnya di HF band komunikasi radio berlangsung.Ionosfer adalah wilayah bagian atas atmosfer di mana ada konsentrasi besar ion dan elektron bebas.Sedangkan ion memberikan ionosfer namanya, tapi itu adalah elektron bebas yang mempengaruhi gelombang radio dan komunikasi radio.Secara khusus ionosfer secara luas dikenal karena mempengaruhi sinyal pada gelombang pendek radio band mana "mencerminkan" sinyal yang memungkinkan sinyal komunikasi radio tersebut untuk didengar melalui jarak yang sangat jauh.Stasiun radio telah lama menggunakan sifat-sifat ionosfer untuk memungkinkan mereka untuk memberikan seluruh dunia cakupan komunikasi radio.Meskipun saat ini, satelit yang banyak digunakan, HF komunikasi radio menggunakan ionosfer masih memainkan peran utama dalam menyediakan cakupan radio di seluruh dunia.Ionosfer meluas selama lebih dari satu daerah meteorologi, meliputi mesosfer dan termosfer, itu adalah daerah yang ditandai dengan adanya ion positif (dan yang lebih penting untuk sinyal radio elektron bebas) dan dari keberadaan ion yang memperoleh namanya.

DasarElektron bebas tidak muncul atas seluruh atmosfer.Sebaliknya ditemukan bahwa jumlah elektron bebas mulai naik pada ketinggian sekitar 30 kilometer.Namun itu tidak sampai ketinggian sekitar 60 sampai 90 kilometer yang dicapai bahwa konsentrasi cukup tinggi untuk mulai memiliki efek yang nyata pada sinyal radio dan karenanya pada sistem komunikasi radio.Hal ini pada tingkat ini yang ionosfer dapat dikatakan untuk memulai.Ionisasi di ionosfer disebabkan terutama oleh radiasi dari MatahariSelain itu, suhu yang sangat tinggi dan hasil tekanan rendah di gas di hulu atmosfer yang ada terutama dalam bentuk monoatomik daripada yang ada sebagai molekul.Di dataran rendah, gas dalam bentuk molekul normal, tetapi sebagai ketinggian meningkatkan bentuk monoatomik lebih dalam kelimpahan, dan pada ketinggian sekitar 150 kilometer, sebagian besar gas dalam bentuk monoatomik.Hal ini sangat penting karena ditemukan bahwa bentuk monoatomik gas sangat jauh lebih mudah untuk mengionisasi daripada bentuk-bentuk molekul.

IonisasiMatahari memancarkan sejumlah besar radiasi semua panjang gelombang dan ini perjalanan menuju Bumi, pertama mencapai daerah luar atmosfer.Dalam menciptakan ionisasi itu ditemukan bahwa ketika radiasi intensitas yang cukup menyerang sebuah atom atau molekul, energi dapat dihapus dari