Inmarsat-4A F4, also known as Alphasat and Inmarsat-XL, is a large

geostationary A geostationary orbit, also referred to as a geosynchronous equatorial orbit''Geostationary orbit'' and ''Geosynchronous (equatorial) orbit'' are used somewhat interchangeably in sources. (GEO), is a circular geosynchronous orbit in altitud ...

communications

I-4 satellite The Inmarsat-4 satellites, or I-4 satellites are a satellite constellation operated by Inmarsat. They provide the Inmarsat BGAN, FleetBroadband, and SwiftBroadband communications networks. They operate on the L band everywhere on Earth ...

operated by United Kingdom-based

Inmarsat Inmarsat is a British communications satellite, satellite telecommunications company, offering global mobile services. It provides telephone and data services to users worldwide, via portable or mobile terminals which communicate with groun ...

in partnership with the

European Space Agency The European Space Agency (ESA) is a 23-member International organization, international organization devoted to space exploration. With its headquarters in Paris and a staff of around 2,547 people globally as of 2023, ESA was founded in 1975 ...

. Launched in 2013, it is used to provide mobile communications to

Africa Africa is the world's second-largest and second-most populous continent after Asia. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 20% of Earth's land area and 6% of its total surfac ...

and parts of Europe and

Asia Asia ( , ) is the largest continent in the world by both land area and population. It covers an area of more than 44 million square kilometres, about 30% of Earth's total land area and 8% of Earth's total surface area. The continent, which ...

. Inmarsat-4A F4 has been constructed by

EADS Astrium Astrium was a European aerospace company and subsidiary of the European Aeronautic Defence and Space Company (EADS), headquartered in Paris. It designed, developed and manufactured civil and military space systems and provided related services ...

and

Thales Alenia Space Thales Alenia Space () is a joint venture between the French technology corporation Thales Group (67%) and Italian defense conglomerate Leonardo (company), Leonardo (33%). The company is headquartered in Cannes, France. It provides space-based ...

based on the Alphabus

satellite bus A satellite bus (or spacecraft bus) is the main body and structural component of a satellite or spacecraft, in which the payload and all scientific instruments are held. Bus-derived satellites are less customized than specially-produced satelli ...

. 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 , and is expected to operate for at least fifteen years.

Arianespace Arianespace SA is a French company founded in March 1980 as the world's first commercial launch service provider. It operates two launch vehicles: Vega C, a Small-lift launch vehicle, small-lift rocket, and Ariane 6, a Medium-lift launch vehicl ...

had been contracted to launch Inmarsat-4A F4, with an Ariane 5ECA rocket, flight number VA-214, delivering it and

INSAT-3D INSAT-3D is a meteorological, data relay and satellite aided search and rescue satellite developed by the Indian Space Research Organisation and was launched successfully on 26 July 2013 using an Ariane 5 ECA launch vehicle from French Guiana.ISRO ...

into

geosynchronous transfer orbit In space mission design, a geostationary transfer orbit (GTO) or geosynchronous transfer orbit is a highly elliptical type of geocentric orbit, usually with a perigee as low as low Earth orbit (LEO) and an apogee as high as geostationary orbit ...

. The rocket lifted off from

ELA-3 ELA-3 () is a launch complex at the Guiana Space Centre in French Guiana. The complex was first used in June 1996 in support of the now retired Ariane 5 Ariane 5 is a retired European heavy-lift space launch vehicle operated by Arianespac ...

Kourou Kourou (; ) is a commune in French Guiana, an overseas region and department of France in South America. Kourou is famous for being the location of the Guiana Space Centre, the main spaceport of France and the European Space Agency (ESA). It ...

at 19:54:07 UTC on 25 July 2013, with Inmarsat-4A F4 separating from the rocket around 27 minutes later. The spacecraft operates in a

geostationary orbit A geostationary orbit, also referred to as a geosynchronous equatorial orbit''Geostationary orbit'' and ''Geosynchronous (equatorial) orbit'' are used somewhat interchangeably in sources. (GEO), is a circular orbit, circular geosynchronous or ...

at a

longitude Longitude (, ) is a geographic coordinate that specifies the east- west position of a point on the surface of the Earth, or another celestial body. It is an angular measurement, usually expressed in degrees and denoted by the Greek lett ...

of 25 degrees east. As of 29 October 2013, it is in an orbit with a

perigee An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values. Apsides perta ...

of , an

apogee An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values. Apsides perta ...

of and 0.14 degrees

inclination Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a reference plane and the orbital plane or axis of direction of the orbiting object. For a satellite orbiting the Eart ...

to the equator. The orbit had a

semimajor axis In geometry, the major axis of an ellipse is its longest diameter: a line segment that runs through the center and both foci, with ends at the two most widely separated points of the perimeter. The semi-major axis (major semiaxis) is the long ...

of and

eccentricity Eccentricity or eccentric may refer to: * Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal" Mathematics, science and technology Mathematics * Off-Centre (geometry), center, in geometry * Eccentricity (g ...

of 0.0003552, giving it an

orbital period The orbital period (also revolution period) is the amount of time a given astronomical object takes to complete one orbit around another object. In astronomy, it usually applies to planets or asteroids orbiting the Sun, moons orbiting planets ...

of 1,435.75 minutes, or 23.92 hours.

European Data Relay System test

The satellite was used as part of an in-orbit verification of the ESA

European Data Relay System The European Data Relay System (EDRS) system is a European constellation of GEO satellites that relay information and data between satellites, spacecraft, UAVs, and ground stations. The first components (a payload and dedicated GEO satellite) w ...

. In 2014, data from the Sentinel-1A satellite in LEO was transmitted via an optical link to the Alphasat in GEO and then relayed to a ground station using a

Ka band The Ka band (pronounced as either "kay-ay band" or "ka band") is a portion of the microwave part of the electromagnetic spectrum. The designation "Ka-band" is from Kurz-above, which stems from the German word ''kurz,'' meaning "short". There ...

downlink. The new system can offer speeds up to 7.2 Gbit/s in the future.

References

External links

EDRS SpaceDataHighway
Spacecraft launched in 2013 Satellites using the Alphabus bus Inmarsat satellites {{UK-spacecraft-stub