France Uses Laser To Link Aircraft, GEO Satellite


PARIS — French military authorities have successfully completed their first series of tests establishing optical laser links between an aircraft and a a satellite in geostationary orbit.

The French arms procurement agency, DGA, and prime contractor Astrium Satellites say the first field operations of the Lola project, a French acronym for Airborne Laser Optical Link, were successfully concluded in six links established between a Lola terminal mounted on a Dassault Mystere 20 business jet and the geostationary-orbiting Artemis satellite owned by the European Space Agency (ESA).

“The first group of tests was to verify the pointing ability of the terminal mounted inside the plane,” Bernard Laurent, head of telecom systems at Astrium, said in a Dec. 14 interview. “This was accomplished. The next steps are to transmit telecommunications data from the airborne terminal to Artemis to verify error rate. Our early results give us confidence that we will have no major problems.”

This first series of tests began in early December. Additional links between the plane and Artemis to demonstrate telecommunications transmissions are scheduled to occur during Mystere 20 flights through May 2007.

During the initial tests the plane was flown at a speed of 300 kilometers per hour at altitudes ranging between 6,000 and 10,000 meters, and Laurent said one link was performed when the aircraft was on the ground. One of the challenges of optical laser communications is minimizing a signal’s degradation as it passes through the atmosphere. The Lola tests were performed mainly in cloud-free conditions, although one was done through light cloud cover, Laurent said.

In a Dec. 13 statement, DGA said the aircraft-to-geostationary satellite transmissions marked a world premiere in the use of laser communications.

The transmission speeds were limited by the Artemis laser terminal’s capacity of 50 megabits per second.

“Beyond the transmission speeds, optical wavelengths offer the unequalled quality of being absolutely discreet and extremely difficult to jam — qualities that offer considerable advantages to forces deployed in a theater of operations,” DGA said in its statement.

Lola is designed to demonstrate whether laser communications with geostationary satellites should be incorporated into future unmanned aerial vehicles.

DGA awarded Astrium a Lola contract valued at 47 million euros ($62 million) in December 2003. It is one of several space-based demonstration projects the DGA is funding to prove technologies for later operational use.

The first Lola results could set up a battle between competing French and German laser-communications technologies, each of which has arguments in its favor. The French and German systems are both vying for a position on board ESA ‘s Alphasat satellite, a large technology-demonstration spacecraft tentatively scheduled for launch into geostationary orbit in 2011.

In an irony that highlights the contrast between Europe’s national governments and its often transnational industrial groups, the laser competition for Alphasat will be between two wholly owned subsidiaries of EADS Space: Astrium Satellites SAS of France and Tesat-Spacecom GmbH of Backnang, Germany.

Tesat’s laser communications terminals have been operated successfully on the ground to demonstrate communications across the atmosphere between terminals placed 140 kilometers apart. They also have been used to communicate with Artemis from the ground. In 2007 Tesat units are scheduled to be tested in orbit on board German government and U.S. Missile Defense Agency satellites in low Earth orbit. The German Aerospace Center, DLR, recently agreed to include a Tesat laser terminal on the TanDem-X radar observation satellite to be launched in 2009.

But Tesat’s terminals have not been mounted on a geostationary satellite. The Artemis hardware is a previous generation of Astrium-built terminals.

ESA’s Alphasat will include a commercial payload to be selected after a competition between Inmarsat of London and a team including Eutelsat of Paris and Telespazio of Rome.

Both Tesat and Astrium would like to mount laser terminals on Alphasat as part of the commercial payload, securing access to an additional 15 years of optical transmissions potential between a geostationary satellite and one of a number of possible user groups including Earth observation satellites in low Earth orbit and unmanned aerial vehicles taking images of hostile terrain.

ESA is planning to build jointly with the European Commission a series of Earth observation satellites called Sentinels, which could carry laser terminals if corresponding technology is certain to be on board Alphasat or some other geostationary satellite over Europe.

The selection of the Astrium or Tesat technology for Alphasat likely will depend more on which government — France or Germany — gives greater financial backing to its industry. The cost of providing a laser terminal for Alphasat has been estimated at around 30 million euros. A decision is expected in mid-2007.

The Artemis satellite, launched in 2001, is expected to continue operations until 2011 despite the fact that it used much of its fuel to climb into proper orbit following a defective launch. The satellite is routinely used by ESA to speed delivery of data from the agency’s large Envisat Earth observation satellite.