PARIS — France’s two identical Spirale satellites launched in February 2009 on a yearlong mission to test missile-detection techniques will remain in operation until the end of 2010 as power degradation issues caused by radiation exposure have proved less severe than anticipated, according to the system’s prime contractor, Astrium Satellites.

Astrium said the Spirale satellites together have collected more than 2 million images to help French military officials design and program a future operational missile-detection satellite. Spirale notably is providing data on the characteristics of the sunlight’s reflection off cloud cover, or from bodies of water, which might otherwise be read as a missile launch, so that the future operational system can avoid false positives as it surveys regions viewed as likely sources of missile launches.

Astrium has contracted with Meteo France, the national weather service, to provide forecasts of areas that will be particularly useful for Spirale to image.

Jean Dauphin, director of Earth observation and science at Astrium Satellites in France, said June 16 that Spirale has fulfilled its contractual objectives for the French arms procurement agency, DGA, and continues to provide data valuable enough to warrant a mission extension.

DGA has outsourced Spirale’s operation and data analysis to Astrium, which performs the work at its Toulouse, France, site. One of the goals of the program is to feed Spirale’s results into a simulator to be used in the design of an operational missile-warning infrared satellite system that France wants to build with its European partners.

The two 117-kilogram Spirale spacecraft, each carrying infrared detectors, operate in a geosynchronous-transfer orbit with a perigee of 600 kilometers and an apogee of 36,000 kilometers.

That is not an optimal orbit for the mission, but was selected to keep Spirale within its demonstration-mission budget of about 124 million euros ($151 million). DGA concluded that the best way to save on launch costs would be to launch the Spirale spacecraft as piggyback passengers aboard a heavy-lift Ariane 5 rocket on a typical Ariane 5 mission of delivering telecommunications satellites to their customary geostationary-transfer-orbit drop-off point.

The Spirale satellites were built by Thales Alenia Space France using the multimission Myriade satellite platform developed by the French space agency, CNES. The platform is designed to be low-cost and does not include a propellant system large enough to power the satellites into a more circular orbit above the Van Allen radiation belts surrounding Earth.

Some of the components were hardened to minimize power loss from the satellites’ regular passage through the radiation belts, but DGA officials had said after the launch that they expected no more than around 12 months of operations.

That has proved overly pessimistic. Dauphin said the radiation effects have been noticed on the satellites, but that the spacecraft continue to deliver usable imagery to build the database to be used for the future system.

French President Nicolas Sarkozy in November 2008 published a military policy paper calling for increased investment in military space assets and, in particular, for development of a missile-warning satellite. None of France’s European Union partners has come forward publicly to announce its financial support for such a system.

DGA officials have expressed frustration at the lack of response and have said France may be willing to move forward on its own. Whether that will be done given France’s current focus on reducing public debt is unclear.

The French government had said it would like to begin development of an operational missile-alert system in 2012, with a launch toward the end of the decade.

Peter B. de Selding was the Paris bureau chief for SpaceNews.