 Full scale mockup Alphasat at Le Bourget Airshow 2013 | |
| Mission type | Communications Technology |
|---|---|
| Operator | Inmarsat European Space Agency |
| COSPAR ID | 2013-038A |
| SATCATno. | 39215 |
| Mission duration | Planned: 15 years Elapsed: 11 years, 8 months |
| Spacecraft properties | |
| Bus | Alphabus |
| Manufacturer | EADS Astrium Thales Alenia Space |
| Launch mass | 6,649 kilograms (14,659 lb) |
| Start of mission | |
| Launch date | 25 July 2013, 19:54:07 (2013-07-25UTC19:54:07Z) UTC |
| Rocket | Ariane 5ECA VA-214 |
| Launch site | KourouELA-3 |
| Contractor | Arianespace |
| Orbital parameters | |
| Reference system | Geocentric |
| Regime | Geostationary |
| Longitude | 25° east |
| Perigee altitude | 35,771 kilometres (22,227 mi) |
| Apogee altitude | 35,801 kilometres (22,246 mi) |
| Inclination | 0.14 degrees |
| Period | 23.92 hours |
| Epoch | 29 October 2013, 17:07:36 UTC[1] |
Inmarsat-4A F4, also known asAlphasat andInmarsat-XL, is a largegeostationary communicationsI-4 satellite operated by United Kingdom-basedInmarsat in partnership with theEuropean Space Agency. Launched in 2013, it is used to provide mobile communications toAfrica and parts of Europe andAsia.[2]
Inmarsat-4A F4 has been constructed byEADS Astrium andThales Alenia Space based on theAlphabussatellite bus. It was the first Alphabus spacecraft to be launched, and as such it carries several experimental communications systems in addition to its commercial payload. The spacecraft had a launch mass of 6,649 kilograms (14,659 lb), and is expected to operate for at least fifteen years.[2]
Arianespace had been contracted to launch Inmarsat-4A F4, with anAriane 5ECA rocket, flight number VA-214, delivering it andINSAT-3D intogeosynchronous transfer orbit.[3] The rocket lifted off fromELA-3 atKourou at 19:54:07 UTC on 25 July 2013,[4] with Inmarsat-4A F4 separating from the rocket around 27 minutes later.[5]
The spacecraft operates in ageostationary orbit at alongitude of 25 degrees east. As of 29 October 2013, it is in an orbit with aperigee of 35,771 kilometres (22,227 mi), anapogee of 35,771 kilometres (22,227 mi) and 0.14 degreesinclination to the equator. The orbit had asemimajor axis of 42,157.20 kilometres (26,195.27 mi) andeccentricity of 0.0003552, giving it anorbital period of 1,435.75 minutes, or 23.92 hours.[1]
The satellite was used as part of an in-orbit verification of the ESAEuropean Data Relay System. In 2014, data from theSentinel-1A satellite in LEO was transmitted via an optical link to the Alphasat in GEO and then relayed to a ground station using aKa band downlink. The new system can offer speeds up to 7.2 Gbit/s in the future.[6]
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