Architecture
Spacebus satellites consist of a satellite bus, which provides power, propulsion, and other subsystems necessary for the satellite's operation, and a payload which is customisable depending on the customer's requirements. The bus was designed to be adaptable to perform various missions; however, as of 2009, only communications satellites have been ordered. It was also designed to be adaptable when the capacity of launch systems increased.
The bus is made of carbon fibre with a composite honeycomb structure. It contains fuel tanks, equipment needed to interface with a carrier rocket, and other critical systems. Panels are attached to the outside of the structure with externally mounted equipment, including the solar panels, payload, and engine. The payload, which is developed separately from the bus, takes up three panels. Once it has been outfitted with transponders or other equipment, it is transported to Cannes-Mandelieu, where it is integrated onto the bus.
Thermal control is achieved by the means of two panels with an aluminium honeycomb structure, which act as thermal radiators allowing the heat generated by the spacecraft to radiate out into space. The radiators were originally produced in Les Mureaux; however, it was subsequently moved to Cannes Mandelieu after the Les Mureaux centre was taken over by EADS. The core structure of the bus is still produced at Les Mureaux. Other parts of the cooling system include insulation, electric heaters, and heat pipes.
The satellites are powered by rigid solar panels. Several configurations are used depending on the amount of power that the satellite is expected to require. The batteries used to store this power are produced by the Belgian company ETCA. Early satellites used nickel-hydrogen batteries, while later spacecraft use lithium-ion batteries.
Most Spacebus satellites use bipropellant, liquid-fuelled chemical engines to achieve their orbits, and subsequently perform station-keeping. Electric propulsion was used on the Stentor and Astra 1K satellites, both of which were subsequently involved in launch failures. A three-axis stabilisation system is used for attitude control.
Read more about this topic: Spacebus
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