SUMMERLAND KEY, Fla. -- By next year, U.S. Homeland Security officials expect to have early results from tests of prototype systems that use satellite communications technology to alert authorities to potential terrorist threats from the sea.

The systems are designed to make it more difficult for terrorists to sneak dirty bombs or pathogens into the United States aboard ships or in shipping containers.

The pilot programs are key elements of the Homeland Security Department's effort to spot suspicious ships and cargo while they are still well out to sea, where a terrorist plot could do little harm, industry and agency officials said.

In one of the projects, the U.S. Coast Guard will use a privately owned communications satellite to relay identification information that commercial ships today broadcast at 30-second intervals to one another and to ports as part of an international network called the Automatic Vessel Identification System. Currently port authorities do not receive this information until the vessels are within range of coastal communications towers or buoys.

The idea is to enable U.S. authorities to identify and track ships much earlier than is possible today. "We want to know, 'Who are they? Where are they? What are they? Where have they been before heading to this country,'" Goward said.

The Orbcomm relay demonstration will not require the installation of any new shipboard equipment or the signing of new international accords, Goward said. "It's information right now that's radiating helplessly off into space," he said.

Having ships actively transmit this information to existing satellites, such as the Inmarsat maritime satellite fleet, would require new international agreements, Goward said. It also would be costly to the shipping companies because of the 30-second broadcast frequency, he said.

Goward said Coast Guard officials understand that ships being operated by terrorists likely would not transmit identification information voluntarily. Other technologies are in development for identifying and tracking these "noncooperative" ships, Goward said.

"It does no good if we develop a technology that costs hundreds of dollars for each shipping container and the industry would have to pay for that. That's not viable," said Kenneth Concepcion, program manager for the Office of Domestic Preparedness.

Millions of shipping containers reach U.S. ports in an average year, industry officials said.

Concepcion declined to discuss details of the container-monitoring concepts, saying the types of sensors and communications links are classified as "security sensitive information."

However, industry officials said the general concept is to install electronic seals on the doors of shipping containers. If terrorists avoided the seals by cutting through the tops or sides of the containers, carbon dioxide or light sensors might detect the intrusion. The container monitors would detect tampering and transmit the data wirelessly to a satellite transmitter aboard the ship. The ship would transmit the data to a satellite system that would relay the information to authorities in the United States.

Tests of the container concepts are under way using actual cargo containers on commercial ships. Concepcion said the tests would run at least through the end of February 2005. The ships will travel to the United States along 19 different shipping routes to demonstrate the geographic reach of the concepts, he said.

Concepcion said it is too early to speculate about the feasibility of monitoring containers on a wide scale. "So far, I've gotten one report in from one leg," he said.

The program will address technical questions, such as whether the radio frequency signals from the containers will interfere with other shipping communications, and whether the systems are compatible with equipment standards and regulations of U.S. trading partners.

The Department of Homeland Security "is not going to say, 'This is our standard and the rest of the world live with it," Concepcion said.

Concepcion said it is too early to speculate about how many of the thousands of containers on the sea at any one time might be outfitted with the monitoring devices. Industry officials said outfitting all containers would be cost-prohibitive.

"Maybe you can't put them on all containers, but you put them on some. And the others, you inspect," said Carl Williams of the California Space Authority, a lobbying group for the state's aerospace industry.