PARIS — A six-satellite constellation dedicated to monitoring maritime traffic for civil defense and environmental security and modeled on the current multinational Disaster Monitoring Constellation could be built and launched for as little as $300 million, according to Daniel Hernandez, director for new programs and systems at the French space agency, CNES.

In a presentation here Feb. 22 at a conference on satellite applications for maritime security organized by the International Astronautical Federation and the Eurisy space-advocacy group, Hernandez said such a constellation has become more feasible now that several dozen nations have expressed interest in building small Earth observation satellites.

But while such spacecraft have become less expensive, their operational utility is limited unless they are used as part of a constellation of spacecraft that would permit daily revisits of the same area.

“There are about 30 nations that have signaled their interest in building small satellites,” Hernandez said. “At the same time, many nations want increased surveillance of maritime traffic — for security, for environmental monitoring and pollution detection.”

Hernandez said the Disaster Monitoring Constellation organized by Surrey Satellite Technology Ltd. of Guildford, England, which features participation by nations that do not have big space budgets, could be the model for a maritime-surveillance constellation. He said the satellites in the constellation could carry optical and radar sensors, and be capable of receiving signals from the Automatic Identification System hardware that oceangoing vessels are supposed to carry starting in 2008.

Hernandez said figures compiled by the International Union of Maritime Insurance show that the maritime insurance market totals $10 billion a year. He said Spanish government authorities have estimated the total cost of the November 2002 Prestige oil-tanker sinking at $9.9 billion.

“When thinking about the cost of satellite-surveillance systems, the costs of environmental damage also should be kept in mind,” Hernandez said.

Many European government officials in recent months have suggested that the most likely terrorist threat is from a small ship approaching the European or U.S. coastline.

The U.S.-led Proliferation Security Initiative, to which more than a dozen nations have subscribed, facilitates boarding and inspection of vessels on the high seas to prevent the spread of weapons of mass destruction. But most of the world’s nations have not yet signed the initiative, and forcibly intercepting such ships in international waters is illegal except in exceptional circumstances.

Alain Claverie of EADS Astrium said a terrorist attack from the sea “is one of the most vulnerable areas for global security. The high seas remain a relatively lawless region.” Claverie said an initial satellite system that permits long-range tracking and identification of ships in international waters could be stitched together from existing and planned radar and optical observation satellites.

Claverie endorsed Hernandez’s idea of having several nations contribute to such a system, each with a relatively modest investment or with existing assets. He noted that Europe already has tested both optical and radio-frequency intersatellite links using the Artemis relay satellite in geostationary orbit and the Spot and Envisat Earth observation satellites in low Earth orbit.

The U.S. government in late 2004 proposed an initial ship-monitoring system, called Long-Range Identification and Tracking of Ships, to the International Maritime Organization (IMO).

The U.S. motivation has been to defend against terrorist attacks on U.S. coasts. Several officials here said this motivation could be married to Europe’s environmental-security concerns to produce an operational system. Both goals require identifying and tracking ships over long distances, and monitoring their cargo.

Yannick Texier of the European Maritime Safety Agency, created by the Commission of the European Union after the December 1999 Erika oil-spill disaster in France and Spain, said the IMO appears on track to adopt the long-range tracking and surveillance system proposal by 2009 or 2010.

Fotis Karamitsos, director for maritime and inland waterway at the European Commission’s Energy and Transport Directorate, said the Erika breakup is a good example of how U.S. security-based concerns and Europe’s safety- and environment-based motivations could come together.

As the stricken tanker continued to disgorge oil, Spanish authorities debated whether to sink the ship in the frigid Atlantic waters, on the assumption that the oil remaining in the ship would freeze in place. They later discovered that the Erika’s oil cargo had been treated with antifreeze materials. Sinking the tanker was thus not a solution.

European and international regulations on automatic cargo identification should make it easier to avoid this kind of confusion, he said.