I
| IAA | International Academy of Astronautics | IAF | International Astronautical Federation | IAG | International Association of Geodesy | IAGA | International Association of Geomagnetism and Aeronomy | IAGC | International Association of Geochemistry and Cosmochemistry | IAMAP | International Association of Meteorology and Atmospheric Physics | IARU | International Amateur Radio Union | IATA | International Air Transport Agency | IAU | International Astronomical Union | IBCN | Integrated Broadband Communication | IBS | INTELSAT Business Service | IBW | Instantaneous Bandwidth | ICAO | International Civil Aviation Organization | ICAS | International Council of the Aeronatical Sciences | ICO | Intermediate Circular Orbit | ICSTI | International Council for Scientific and Technical Information | ICSU | International Council for Scientific Unions | IDR | Intermediate Data Rate | IEC | International Electrotechnical Commission | IEE | Institution of Electrical Engineers | IEEE | Institution of Electrical and Electronics Engineers | IF | Intermediate Frequency | IFF | Identification Friend or Foe | IFL | International Frequency List | IFRB | International Frequency Registration Board (ITU-R) | IFRC | International Frequency Registration Circular (ITU-R) | IIASA | International Institute of Applied Systems Analysis | IISL | International Institute of Space Law | ILS | Instrument Landing System | IMASS | Intelligent Multiple Access Spectrum Sharing | IMO | International Maritime Organization | IMT | International Mobile Telecommunications | IMT-2000 | International Mobile Telecommunication System | INAF | National Institute for Astrophysics (I) | INMARSAT | INternational MAritime SATellite organization | INPE | Instituto Nacional de Psequisas Espaciais | INSU | Institut National des Sciences de l'Univers (F) | INTA | Instituto Nacional de Tècnica Aerospacial | INTELSAT | International Telecommunications Satellite Organization | ION | The Institute of Navigation (US) | IR | Infrared | IRAM | Institut de Radio Astronomie Millimétrique | IRG | Independent Regulatory Group (EC) | IRT | Institut für Rundfunktechnik (D) | ISAR | Inverse Synthetic-Aperture Radar | ISAS | Institute of Space and Astronautical Science | ISDN | Integrated Services Digital Network | ISL | Inter-Satellite Link | ISM | Industrial, Scientific, Medical | ISO | International Organization for Standardization | ISR | Incoherent Scatter Radar | ISRO | Indian Space Research Organization | ISS | Inter-Satellite Service | IT | Information Technology | ITA | Industrial Telecommunication Association (USA) | ITFS | Instructional Television Fixed Service | ITU | International Telecommunication Union | ITU-D | International Telecommunication Union - Telecommunication Development Sector | ITU-R | International Telecommunication Union - Radiocommunication Sector | ITU-T | International Telecommunication Union - Telecommunication Standardization Sector | ITWG | International TOVS Working Group | IUCAF | Scientific Committee on the Allocation of Frequencies for Radio Astronomy and Space Science (UNESCO) | IUGG | International Union for Geodesy and Geophysics | IVS | International VLBI Satellite | IWG | Intersessional working group (of the SFCG) | IWP | Interim Working Party (ITU-R) | IZMIRAN | Institute of Terrestrial Magnetism, Radio Research and the Ionosphere (Russia) | |