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Maritime Mobile Service Identity - MMSI is a unique 9 digit number and acts in the same way as a telephone number. The MMSI allows radio operator to make automatic calls through VHF DSC radio and is the identity that is automatically transmitted within DSC calls. These MMSI numbers are issued by the appropriate authorities in the country of registration of the vessel and can be referenced back to a database of information about the vessel and it’s owners and so forth.
Maritime Safety Information - Navigational and meteorological warnings, meteorological forecasts, and other urgent safety-related information broadcast to ships.
Maximum Usable Frequency is the frequency at which radio communications just starts to fail. It is caculated by formula: MUF=f0/cos alpha where is
h= layer height
f0= layer density
alpha = arc tg ((d/2)/h)
Narrow Band Direct Printing
NCS Network Co-ordination Station. This is the land earth station within the Inmarsat Oceanan Region which is responsible for a smooth communication proces. This station is directing the mobile users and the Land Earth Stations to the right appointed channel.
Nautical Mile - A nautical mile or sea mile is a unit of length. It corresponds approximately to one minute of latitude along any meridian. The international standard definition is: 1 NM = 1,852 m exactly.