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Automatic Identification System (AIS)
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AIS is an automated system installed on maritime vessels for reporting ship information, such as location, heading, and speed. AIS signals are received by land-based systems, ocean-based data buoys, and space satellites, and then integrated into a centralized dynamic database. AIS is used worldwide, although regional differences in frequency are permitted.
According to the U.S. Coast Guard, AIS "transmissions use 9.6 kb GMSK FM modulation over 25 or 12.5 kHz channels using HDLC packet protocols...The system is backwards compatible with digital selective calling systems, allowing shore-based GMDSS systems to inexpensively establish AIS operating channels and identify and track AIS-equipped vessels, and is intended to fully replace existing DSC-based transponder systems."
Some AIS transmissions in oceanic regions, far removed from terrestrial base stations, are received by satellites. Providers or potential providers of AIS information via satellite include Orbcomm, which will include AIS receivers on its 18 second-generation satellites, expected to be in orbit by 2014. Until that time, Orbcomm opeates two microsatellites (one in equatorial orbit and one in polar orbit) to provide AIS coverage. The microsatellites were launched in October 2011 and January 2012.
Other companies planning to offer satellite-based AIS coverage include SpaceQuest LTD, and exactEarth of Canada.
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Frequencies |
| Frequency | Bandwidth | Use | Service | Table |
| 161.975 MHz | 25 kHz | AIS 1 | Maritime Mobile | - |
| 162.025 MHz | 25 kHz | AIS 2 | Maritime Mobile | - |
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