| Inmarsat-4 F3 | |
| Operator: | Inmarsat |
| Spacecraft Bus: | Eurostar E3000 |
| Manufacturer: | EADS Astrium |
| Launch Mass: | 5960kg (13,140lb) |
| Launch Site: | Baikonur 200/39 |
| Entered Service: | 7 January 2009 |
| Orbit Reference: | Geocentric |
| Orbit Regime: | Geostationary |
| Orbit Longitude: | 98° West |
| Apsis: | gee |
Inmarsat-4 F3 is a communications I-4 satellite operated by the British satellite operator Inmarsat. It was launched into a geosynchronous orbit at 22:43 GMT on 18 August 2008,[1] by a Proton-M/Briz-M Enhanced carrier rocket. It is currently located at 97.65° West longitude, providing coverage of the Americas.[2] It entered service on 7 January 2009.
Like the earlier Inmarsat-4 F1 and F2 satellites, Inmarsat-4 F3 was constructed by EADS Astrium, using a Eurostar E3000 bus. It has a mass of 5,960 kilograms, and is expected to operate for 13 years.[3] It was originally slated for launch using an Atlas V 531, but was transferred to Proton due to a large backlog of Atlas launches.
In the United States, Inmarsat ground stations are licensed to operate at 1525-1559 MHz and 1626.5-1660.5 MHz. The 1544-1545 MHz and 1645.5-1646.5 MHz bands are reserved for safety and distress communications.