INMARSAT PLANS a flight trial of its new Aero-I satellite-communications (satcom) service in January 1996. The service, allowing use of smaller, cheaper, avionics and antennae, will become available with the launch of new Inmarsat 3 communications satellites early in 1996.

Spotbeams will be used to concentrate satellite power, allowing use of smaller, lower-gain, antennae than those required for the present Aero-H voice and data service. Inmarsat estimates that Aero-I satcom systems will weigh 20-50kg, compared with 80-120kg for Aero-H equipment, and cost $50,000-100,000.

Aero-H equipment is widely fitted to long-haul airliners, and the introduction of the Aero-I is expected to make satcom affordable for short- and medium-haul aircraft. Spotbeams will cover most of the Northern Hemisphere, but there will be gaps in Southern Hemisphere coverage, notably over New Zealand.

The January trial will involve a Cessna Citation business jet equipped with CAL avionics and an experimental antenna developed by Canada's Communications Research Council. This automatically aligns with the Earth's magnetic field, to point at the geostationary satellite without needing a steering input from the aircraft's inertial-reference system. The trial will use an Inmarsat 2 global beam to emulate a spotbeam.

Inmarsat says that Canadian Marconi (CMC), Sensor Systems and Toyocom are developing Aero-I antennae, while Ball Aerospace is developing avionics and antenna for the new service. CMC says that its CMA-2200 top-mounted antenna will be 760mm long, 100mm high and 75mm wide. By comparison, its CMA-2102 top-mounted Aero-H antenna weighs almost 30kg, and is 1.7m long, 120mm high and 470mm wide. The new antenna will be "significantly cheaper", and will be suitable for aircraft "from the Boeing 767 downwards", says product manager Mike Maritan.

The Aero-I will offer essentially the same voice, facsimile and data services as those available from the Aero-H. Voice signals will be transmitted at 4.8kbit/s, compared with 9.6kbit/s for the Aero-H, although the half-rate is part of an Aero-H Enhanced service which is planned to take advantage of the spotbeams, says Inmarsat.

In-Flight Entertainment International newsletter (31 October) reports that some satcom equipment makers and service providers see few advantages in the Aero-I unless Inmarsat makes it more cost-attractive.

Source: Flight International