1. Aircraft Earth Station (AES)
The AES terminals are on board aircraft-installed radio communication sets capable of communicating via satellite with Ground Earth Stations (GES) in the Inmarsat Satellite Network for access to Terrestrial Telecommunication Networks (TTN). The Inmarsat at first, and Globalstar and Iridium satellite operators later, were developed several standards of AES for installation on board of civil and military airplanes and helicopters. The Inmarsat AES terminal receives and process RF signals from the satellite, then format and transmit RF signals to the satellite at L-band (1,6/1,5 GHz). The AES interfaces on board systems, such as duplex Tel, Fax, data and video equipment for aircraft, which standards meets the requirements of the ICAO and industry standards such as ARINC Characteristics 741 as well as Inmarsat standards. In this case, Inmarsat is not concerned with packaging, and only requires compliance to its SDM (System Definition Manual) for ground system access. In fact, ARINC 741 describes one physical implementation of the Inmarsat system, which Characteristics 741 for AES comprises Above Cockpit Units (ACU) and Below Cockpit Units (BCU) illustrated in Figure 1. The BCU are electronic elements of transceiver unit usually installed inside of the pilot cabin (cockpit), while ACU are mounted on either top or sides of the aircraft fuselage frame. The main elements of BCU and ACU units are as follows: