Glossary of terms and abbreviations AAIC: Accounting authority for satellite traffic invoicing. A/D: Analogue-to-digital signal conversion. ADE: Above decks equipment. The electronic and mechanical equipment above decks on a ship. AFC: Automatic frequency control. AGC: Automatic gain control. AHC: Ampere hour capacity. The figure used to indicate the quantity of energy which may be delivered by a specific battery for a stated time period. ALOHA: A random access protocol for accessing a packet satellite network. Developed at the University of Hawaii and using the Hawaiian word for greeting. AM: Amplitude modulation. AMERC: The Association of Marine Electronic and Radio Colleges (based in Great Britain). AORE: Atlantic Ocean region east. AORW: Atlantic Ocean region west. APC: Adaptive predictive coding. Apogee: The furthest point which a satellite reaches in its orbit from the earth. ARQ: Automatic request repeat. An error control protocol used in data communications. The RX is able to request the retransmission of packets received in error. ASCII: American Standard Code for Information Exchange. ASMl and 2: At-sea-maintenance qualifications, level one and two. Azimuth: Surface angle extended between a line of longitude and a specific direction. Baud: Standard unit of signalling at a rate of one signal element/second. BCH: Bose-Chadhuri-Hocquenghem code. BDE: Below decks equipment. The electronic/mechanical equipment of an SES inside the ship. BE: Billing entity. An accounting authority for satellite traffic invoicing. BER: Bit error rate. The number of bits transmitted that are received with errors, compared with the total number of bits transmitted. BITE: Built-in test equipment. BPSK: Binary-phase-shift keying. Modulation method containing two states of phase shift. 288 Glossary of terms and abbreviations C-band: Name of frequency band used for satellite links with a fixed station. Approximately 6/4 GHz. CCIR: Comite Consultatif International des Radiocommunications. CCITT: Comite Consultatif International Telegraphique et Telephonique. CDMA: Code-division multiple access. CEPT: Conference of European administrations. CES: Coast earth station. C/N: Carrier-to-noise ratio. C/No: Carrier-to-noise spectral density. Companding: The process of compression and expansion of the baseband signal in a communications link. COMSAT: Communications Satellite Corporation. Convolution coding: A system of encoding data bits for FEC. COSPAS: Cosmicheskaya Sistyeme Poiska Avariynich Sudov. COSPAS-SARSAT: International satellite-based emergency alerting and locating system. CSC: Common signalling channel. D/A: Digital-to-Analogue signal conversion. dB: Decibel. DCE: Data circuit terminating equipment. Demand assignment: A system whereby communications channels are assigned on demand from a common pool. Demodulator: The receiver circuitry which reproduces the baseband signal from the received signal. DeMUX: The method of extracting, at the receiver, multiplexed signals from a common carrier frequency. Discriminator: An FM demodulator circuit. DMG: Distress message generator. DM: Delta modulation. DoR: Data over radio. Downlink: Link from satellite to ground. DSC: Digital selective calling. An NBDP transmission used for priority alerting within the GMDSS. DTE: Data terminal equipment. Duplexer: A circuit which enables both the TX and RX stages in a transceiver to operate simultaneously. Duplex operation: Two way communication operation using two frequency channels permitting simultaneous transmit/receive. EGC: Enhanced group call. Group calling on Inmarsat-C. EIRP: Effective isotropically radiated power. The measure of the effectiveness in radiating transmitted power in relation to a theoretical isotropic antenna. ELT: Emergency locator transmitter. Airborne distress beacon in theGMDSS. ELV: Expendable launch vehicle. EME: Externally mounted equipment. ENT: Equivalent noise temperature. EPIRB: Emergency position indicating radio beacon. Maritime beacon used in the GMDSS. Glossary of terms and abbreviations 289 Error rate: The ratio of the incorrectly received to the correctly received bits in a data system. ESA: European Space Agency. FDM: Frequency division multiplexing. FDMA: Frequency-division multiple access. Method of user access to a frequency band by access to small frequency slots. FEC: Forward error correction. FleetNET: Inmarsat EGC-based system permitting shipowners to broadcast to some, or all, of their fleet. FM: Frequency modulation. Forward link: The fixed-to-mobile link. Frequency spectrum: The finite resource used for the propagation of radiowaves. From-mobile: The inbound calling direction. GEO: Equatorial geostationary orbit. GES: Ground earth station. GF: Gold Franc. GMDSS: Global maritime distress and safety system. GRT: Gross registered tonnes. G/T: Gain-to-noise temperature ratio. Half duplex channel: A channel which is only capable of passing information in one direction at a time. HEO: High elliptical orbit. HPA: High power amplifier. H3E: Amplitude modulation mode containing full carrier power and one intelligent sideband. HSD: High-speed data. ID: SES identification number. See IMN. IFRB: International frequency registration board. Prevents chaos by allocating frequencies in accordance with radio regulations. IME: Internally mounted equipment. IMF: International Monetary Fund. IMN: Inmarsat mobile number. MES identification number. Also known as the SES identification number ID. IMO: International Maritime Organization. INM2: Second generation of Inmarsat satellites. INM3: Third generation satellites. Inmarsat: International Maritime Satellite Organization. Inmarsat-A: Current main sat-com system for voice/data. Inmarsat-B: New system using all-digital technology. To replace Inmarsat-A. Inmarsat-C: Current small, cheaper sat-com system for data only. Inmarsat-E: L-band Inmarsat emergency position indicating radio beacons. Inmarsat-M: An all-digital cost effective sat-com system. Intelsat: International telecommunications satellite consortium. Intermodulation: Interference caused by adjacent frequency division multiplexed carriers modulating with each other. lOR: Indian Ocean region. ISB: Independent sideband operation. ISDN: Integrated services digital network. ISL: Interstation signalling link. 290 Glossary of terms and abbreviations ISO: International organization of standardization. ITA: International telegraph alphabet code. ITU: International Telecommunications Union. 13E: Amplitude modulation mode containing virtually zero carrier power and one intelligent sideband. Lambda (A): The Greek character used to denote wavelength. L-band: Frequency band used for links between mobile and satellites. Approximately 1.5/1.6 GHz. LEO: Low earth orbit. LES: Land earth station. Link call: Terminology used to describe a duplex radio-telephone call. LNA: Low noise amplifier. LUT: Local user terminal. An earth station in the Cospas-Sarsat system. Marisat: The original maritime satellite communications system. Established in 1976 by a US consortium and taken over by Inmarsat in 1982. MCC: Mission control centre. Controls RCCs in Cospas-Sarsat system. MCS: Maritime communications sub-system on the Intelsat V generation of satellites. MERSAR: Merchant Ship Search and Rescue manual. Produced by the IMO. MES: Mobile earth station. MID: Maritime identification digits MTBF: Mean time between failures. MMSI: Maritime mobile service identity number. MMSS: Maritime mobile satellite service. Modem: Analogue-to-digital, and vice versa, modulator for data transmission on analogue circuits. Modulator: The circuit in a transmitter which mixes the baseband signal with the carrier frequency. MRCC: Maritime Rescue Coordination Centre. MSI: Maritime safety information. MSS: Mobile satellite services. MTBF: Mean time between failures. A measure of the reliability of electronic equipment. MUF: The maximum usable frequency. Multiplexing: The term used for a method whereby a number of signals are modulated onto a common carrier. Occasionally abbreviated to MUX. NASA: National Aeronautics and Space Administration. NAVAREA: IMO global navigational area. Navtex: NBDP broadcasting system for maritime safety information. NBDP: Narrow band direct printing. Narrow band transmission of teletype text. NCC: Network control centre. NCS: Network coordination station. NOAA: National Oceanic and Atmospheric Administration. OCC: Operations control centre. Inmarsat. OTF: The optimum traffic frequency. Glossary of terms and abbreviations 291 O-QPSK: Offset quaternary-phase-shift keying. PABX: Private automatic branch exchange. Packet: A self-contained component of a message which can be transferred as an entity in a data communications system. Contains the address, control and data signals. pc: Personal computer. PCM: Pulse code modulation. PEP: Peak envelope power. Perigee: The closest point to the earth of a satellite in earth orbit. PFD: Power flux density. Phased array: An antenna assembly whose directivity is controlled by signal phasing and not by mechanical means. PLB: Personal locator beacon (land). PM: Phase modulation. Polarization: The orientation in space of the electric field of a radiowave. Polling: A service whereby selected MESs are interrogated. POR: Pacific Ocean region. Priority 3: Inmarsat designation for distress calls via satellite. Protocol: A discipline controlling the operation of a system. PSDN: Public switched data network. PSPDN: Public switched packet data network. PSTN: Public switched telephone network. PSK: Phase-shift keying. The