Lockheed Martin plans to widen its study into using commercial satellites for military telecommunications following the successful demonstration of a call from a supersonic F-16 fighter using the Iridium low-earth orbit constellation.

Commercial off-the-shelf communication systems are being viewed as a low-cost alternative to increasingly oversubscribed military satellites. The intention is eventually to extend the availability of space-based communications to fighters reliant on UHF/VHF line-of-sight communications.

"We're creating the opportunity for a wireless global area network. We're looking at the F-22 and Joint Strike Fighter being recipients. There is also interest from other countries looking for low-cost commercially available satellite communications," says Floyd Whitehouse, Lockheed Martin director of information operations.

Lockheed Martin hopes to go beyond voice communications with the current L-band Iridium system to include data and image transmission. This would allow for en route transmission of retargeting information, the relay of external sensor data, real time battle-damage assessment, or would simply enable the pilot to communicate directly with anywhere in the world.

Consideration has also been given to incorporating the system as part of the pilot's survival suit.

The F-16 demonstration entailed installing a "phone in a box" in the aircraft's avionics bay. The AlliedSignal AIRSAT 1, which was hardwired to a dorsal-mounted low-gain blade antenna, could be switched between incoming calls and outgoing speed dialling. Voice contact was maintained through a variety of manoeuvres, up to a speed of Mach 1.6 and an altitude of 42,000ft (12,800m). Sound was temporarily cut while the aircraft was inverted because of the absence of an underside antenna.

Attention has turned to extending the available satellite band width to facilitate data and imagery transmissions. With Iridium in Chapter 11 bankruptcy protection, Lockheed Martin has opened initial talks with GlobalStar on future communication system capabilities. The company is also looking at the planned Teledesic system. "We'll grow as they grow, piggybacking off commercial technology," says Whitehouse.

Meanwhile, the next phase of the programme will start in November, involving the integration of telecommunications data with the aircraft's 1553 avionics, enabling the storage of information or display of imagery. Lockheed Martin will also join the Space Warfare Centre to test the vulnerability of commercial satellites to jamming or interference.

The US Air Force, in the meantime, is conducting its own commercial satellite tests during the current JEFX99 military exercise. This is understood to have involved fitting a second AIRSAT 1 communications system to a Boeing KC-135 tanker.

Source: Flight International