Inmarsat-4A F4, also known as Alphasat and Inmarsat-XL, is a large geostationary communications I-4 satellite operated by UK-based Inmarsat in partnership with the European Space Agency. It is used to provide mobile communications to Africa and parts of Europe and Asia.

Inmarsat-4A F4 has been constructed by EADS Astrium and Thales Alenia Space based on the Alphabus satellite 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.

INSAT-3D is a meteorological, data relay, and satellite-aided search and rescue satellite developed by the Indian Space Research Organisation. The satellite has many new technology elements like a star sensor, micro-stepping Solar Array Drive Assembly (SADA) to reduce spacecraft disturbances, and a Bus Management Unit (BMU) for control as well as telecom and telemetry functions.

The mission goal is stated as "to provide an operational, environmental & storm warning system to protect life & property and also to monitor earth’s surface and carry out oceanic observations and also provide data dissemination capabilities."