A modern Satellite-C terminal, suitable for a fishing boat, is now about the size of a car radio. The terminal is relatively inexpensive, simple to operate and enables secure messaging which costs less than half a pence per character.
The International Maritime Satellite Organisation (InMarSat), controls satellite communications for ships. The group was established in 1979 by the International Maritime Organisation (IMO) and is a totally independent organisation consisting of almost 90 member countries including the UK.
The Inmarsat system works through a total of four satellites (with backups in case of failures). Two are above the Atlantic Ocean, one above the Indian Ocean and one above the Pacific. They orbit the earth at a distance 22,223 miles in an area of space known as the Clarke Belt. At this distance from the earth the orbital speed of the satellite (about 1.6 miles every second) locks-in with the rotational speed of the earth so the satellite appears to remain stationary over a fixed point on the earth. It's all down to matching angular velocities between the earth and satellite.
The gravity of the Earth, Moon and Sun all try to pull the satellite out of the stable orbit, so all satellites carry their own supply of rocket fuel to help keep them in position. However, when this fuel runs out they drift off station and will cease to function, which is one of the reasons the satellites only have a lifespan of about 12- 15 years.
All signals to and from the satellite must be transmitted through a Land Earth Station (LES). There are many in the world, and the UK station, which is operated by British Telecom, is located at Goonhilly in Cornwall. Goonhilly is linked with other land earth stations around the world, enabling 24 hour global coverage to be maintained from this one location.
The two main systems suitable for fishing vessels are the Satellite-C and the new Maritime Mini-M, but it is likely other systems shall be available in the near future. Both systems have their good, and not-so-good, points.
Satellite-C is small, light, inexpensive, low power, simple, has no standing charges and is very easy to use. It's a no-nonsense secure, reliable communications system and a cornerstone of GMDSS which is already fitted in around 500 UK fishing vessels. It has full distress capabilities and will receive the free weather forecasts and navigation warnings not covered by Navtex. Most Sat-C terminals now have a built-in GPS facility so only one antenna is needed for both navigation and communication. It can easily link up with e-mail, so if you have a home PC and modem you can send and receive messages from your own living room. However, no voice communication is possible with the satellite-C since it is a text and 'from ship' fax system only. This can make very long messages expensive, though a simple data compression programme from your local computer supplier can reduce messaging costs significantly.
The new Maritime Mini-M system uses the 'spot beam' facilities on satellites and has the advantages of being small, light and low power. Also, it provides voice, fax and data communications and works four times faster than the Sat-C. However, it is not approved for GMDSS, is roughly twice the price of a Sat-C, has monthly standing charges and requires a small stabilised aerial.
The GMDSS implementation deadline of the 1st February 1999 is now just 15 months away. Soon after this date Stonehaven Radio, Wick Radio and all the other BT radio stations will close. A full and comprehensive distress and safety watch will be maintained by the Coast Guard but not a commercial service. If a skipper needs to make an MF or VHF radio telephone call to the home or the office he will have to use a foreign radio station such as Lyngby in Denmark. Some skippers may consider fitting SatComms sooner than later to avoid any last minute stampede as February 1999 approaches.
Skippers and owners who decide to fit SatComms should request the MSA to exempt the vessel from carriage of the main and/or the reserve MF R/T equipment (required under Merchant Shipping Rules) to reduce maintenance costs. Each application is considered on an individual basis and the local Radio Surveyor can provide assistance and guidance.