Inmarsat Communications

Standard satellite communications is conducted via INMARSAT, the International Maritime Satellite System based in London, England. The maritime satellite system has three major components: the space segment provided by INMARSAT, the Coast Earth Stations (CES) provided by INMARSAT signatories and SES (Ship earth station).

INMARSAT establishes equipment standards and operates the satellite (space) segment. Private companies operate the land (earth) segments that connect with local and international telecommunications networks. There are several INMARSAT systems. Each offers a range of services and capabilities.

INMARSAT-A is the original analog system offering telephone and telex services. INMARSAT-A will eventually be replaced by INMARSAT-B which is a digital system having more channels and a higher data transfer rate. INMARSAT-C is a digital telex system with EGC/SafetyNet capability, and INMARSAT-M is a compact digital system with voice and data capability but does not have telex. INMARSAT A, B and M are real-time systems (i.e. on-line direct contact). INMARSAT-C is a store and forward system (i.e. sent to a CES and then forwarded). The advantage INMARSAT-C is that it has EGC capability for reception of SafetyNet/MSI messages. Being able to receive SafetyNet satisfies requirements for receiving MSI in sea areas outside coastal NAVTEX coverage. NOTE: HF NBDP telex is used outside INMARSAT coverage.

The INMARSAT space segment consists of four satellites in geostationary orbit over the equator. Each satellite provides an area of coverage roughly from 70° N to 70° S and roughly 70° of longitude to either side of its meridian. Although there is overlap in coverage, particularly in the Atlantic, there is one satellite for each of the ocean regions. Vessels using INMARS A, В or M when first turning their SES on or when changing ocean regions may have to align their antenna to the satellite. This is usually done by specifying the satellite and entering an azimuth and elevation angle to the satellite. Some newer SATCOM use the nav-input to align the antenna automatically. Vessels using INMARSAT-C simply specify the satellite and lock-on is automatic (SAT-C antenna is omni directional). In either case, if you are not able to lock-on, it may be that the antenna is being shaded by the ship's structure or other obstruction. You may have to wait, change course or change satellites. If you do temporarily change satellites, remember to return to the correct satellite for your region.

Calls from shore to ship or ship to ship are made by dialing the ocean area code and the ship's (SES) ID number. NOTE: Ships with more than one SES terminal or having both INMARSAT-A and С will have more than one ID number.

INMARSAT traffic is handled according to its priority. Obviously distress is the highest priority. Distress traffic (PRIORITY 3) is automatically routed to an RCC. Priority codes are as follows:

PRIORITY 0 Routine (ship's business, reports, etc.)

PRIORITY 1 Safety (navigation or weather warnings)

PRIORITY 2 Urgent (safety of vessels or persons)

PRIORITY 3 Distress (own ship or distress relay)

Calls from ship to shore require a coast earth station (CES) ID number, followed by a service code, country code, area code and telephone or telex number.

Coast earth stations use two digit ID codes for SAT-A and three digit ID codes for SAT-C, В and M.

To facilitate sending an automatic distress (red button), some satellite equipment require an ocean region and coast earth station be designated immediately at turn-on (logging-on). Obviously the satellite and coast earth station should be in your ocean region. In some cases you also have to specify an RCC. Make sure you update this during the voyage if you change ocean regions. If the wrong ocean region is entered, the distress call may be routed to the wrong RCC, which will delay the response. All distress and safety traffic receives priority handling by INMARSAT and is routed by the CES to the regional RCC without cost.

SafetyNET

SafetyNet is a service of INMARSAT-C for receiving distress alerts and maritime safety information (MSI). Vessels operating beyond coastal NAVTEX coverage must have INMARSAT-C or HF NBDP telex to receive maritime safety information. SafetyNet, like NAVTEX, can be programmed by the ship's operator to accept or reject certain message categories.

SafetyNet is available only in SAT-C terminals with the Enhanced Group Call (EGC) feature. EGC is used for sending messages to groups of ships or to all ships within a specified region or NAVAREA. To receive SafetyNet broadcasts appropriate to your location or NAVAREA you must use the satellite serving your ocean region. This will ensure that you receive the MSI broadcasts for your NAVAREA. If you do not specify a satellite, the receiver will usually lock on to the highest visible satellite, which could be a problem in areas of overlapping coverage. You must also log-on to the system. In INMARSAT-C logging on is usually accomplished as soon as you specify the satellite. This tells the NCS that you are accepting traffic.

NOTE: You must logout before turning your system off or the NCS will assume you were receiving messages while your system was off. When you next log-on again, you will receive the safety messages that are still in affect at the next broadcast.

To receive SafetyNet:

1. Use your own ocean region satellite (you must log-on). 2. Specify the NAVAREA you want (you can also request the next NAVAREA). 3. Indicate message categories to be rejected (same as NAVTEX). 4. Nav position must be updated (usually automatic).

II. Put 15 special questions to the text.

3. Translate the following words and expressions from English into Russian

Standard satellite communications, the International Maritime Satellite system, the satellite (space) segment. international telecommunications network, analog (digital) system, EGC, omni-directional, coast earth station, log on / log out , SES.

4. Translate the following sentences from Russian into English

   1. В ГМССБ задействованы спутниковые и наземные системы связи.

   2. ИНМАРСАТ основывается на использовании геостационарных спутников.

   3. ИНМАРСАТ обеспечивает оповещение о бедствии, передаваемое с использованием судовой земной станции или спутникового аварийного радиобуя (АРБ) и возможность двусторонней связи с абонентом.

   4. Космический сегмент, предоставляемый ИНМАРСАТ, - спутники, запущенные на геостационарную орбиту.

   5. Спутники располагаются в определенных точках над Атлантическим, Индийским и Тихим океанами и обеспечивают почти глобальный охват поверхности Земли.

   6. Наземный сегмент включает в себя глобальную сеть береговых земных станций и координирующих станций сети (NetworkCoordinationStation).

   7. Береговые земные станции (БЗС) обеспечивают линию связи между спутником и наземными сетями связи и одновременно могут представлять несколько каналов для связи с судовыми земными станциями.

   8. Судовые земные станции – это терминалы связи, установленные на борту судна.

   9. Судовые земные станции предназначены для связи с береговыми абонентами через спутник и БЗС.

   10. Связь береговых земных станций со спутником осуществляется через большую направленную антенну.

5. Read, translate and retell the text below

Satellite communications are particularly important elements of the GMDSS. The INMARSAT system employs geostationary satellites and operates in the 1.5 – 1.6 GHz. It provides ships fitted with Ship Earth Stations (SES) a means of alerting and a capability of two-way communications using radio telex and radiotelephone.

The INMARSAT SafetyNET system is used for broadcasts of MSI to areas not covered by the NAVTEX system.

The maritime satellite system has three major components: the space segments provided by INMARSAT, the Coast Earth Stations (CES) provided by INMARSAT signatories and SESs.

The INMARSAT system provides ships at sea with the same types and quality of modern communications as are available ashore. The nerve center of the system is the Operations Control Center (OCC) located at INMARSAT‘s headquarters in the United Kingdom. Four INMARSAT satellites in geostationary orbit 36,000 kilometers above the equator provide near-global coverage. The coast earth stations CES provide the link between the satellites and terrestrial telecommunications networks.