PARIS — A group on the U.S. State Department’s list of terrorist organizations has been using a vacant Ku-band transponder on an Intelsat satellite to broadcast its message in Sri Lanka and the surrounding region without Intelsat’s knowledge, sparking a protest from the Sri Lankan government. Intelsat in turn has vowed to put a stop to it.

One industry official said Intelsat’s attempt to re-point the satellite beam in question so that it does not cover Sri Lanka — a move that presumably would lead the terrorist group, the Liberation Tigers of Tamil Eelam, to abandon their broadcasts — has been slowed by an unexpected source: satellite-fleet operator Eutelsat of Paris.

Eutelsat competes with Intelsat in most regions of the world but in this case is a customer on the beam in question.

Intelsat’s trouble in South Asia is the latest example of signal piracy and jamming in the commercial satellite sector, a phenomenon that some industry officials say is likely to increase in Asia and Africa as satellite television becomes more ubiquitous and technical know-how becomes more readily available.

Concerns that piracy and jamming threaten the credibility of commercial satellites among some potential users, especially military customers, have been raised repeatedly in recent years.

To open this potential new market, EMS Technologies Inc. of Norcross, Ga., has begun pitching commercial companies on the benefits of its existing anti-jam antenna technology, which up to now has been used only for military and dual-use satellites .

Michael Fatig, vice president of business development for EMS’s Defense and Space Systems division, said the company’s latest nulling antenna design is substantially smaller and less expensive than its predecessors following research investment by the U.S. Department of Defense.

He conceded that despite this progress, the limited number of units produced in a given year has kept costs relatively high, at $10 million to $20 million apiece, or between 5 percent and 8 percent of the total cost of a commercial telecommunications satellite.

In an April 12 interview, Fatig said the technology has been well-proven aboard military satellites and that the only debate is whether satellite operators can justify the cost by the potential savings.

“The question now is purely one of economics,” Fatig said. “What is the potential revenue loss [to piracy or jamming]? What is the impact of these losses on overall revenues, and on the credibility of the service to customers?” A nulling antenna senses high-power sources within the geographic coverage of the antenna and blocks the signals from interfering with the satellite’s normal transmissions. The technology has been supported in Europe with research investment money from the European Space Agency.

For Intelsat, the signal hijacking by a group backing the Liberation Tigers of Tamil Eelam of Sri Lanka did not result in the loss of revenues because the group, which has been waging a war against the Sri Lankan government for years, did not deprive a legitimate customer from making broadcasts.

Instead, the group — based at one or more areas in which their satellite Earth station could remain operational without fear of government discovery — used a vacant Ku-band transponder on the Intelsat 12 satellite, located at 45 degrees east longitude over the Indian Ocean.

Intelsat Chief Counsel Phillip L. Spector said that to his knowledge it is the first time an organization that has never been a customer of Intelsat has conducted such an operation.

“These people are grabbing vacant space on the satellite and they are stealing from Intelsat,” Spector said in an April 12 interview. “It is outright stealing. They have never been authorized to use our satellite.”

Demonstrating a technical expertise that is not within everyone’s reach, the signal theft resembles the case of squatters taking up residence in a vacant apartment in a large complex in which the landlord does not perform weekly occupancy surveys.

Spector said Intelsat’s satellite control teams monitor the health of the company’s 51-satellite fleet but do not regularly verify the source of each and every television program. In the cases of signal piracy that have occurred in China, dissident groups have used high-powered Earth stations to override a broadcaster’s programming to beam their propaganda for brief periods before disappearing.

In this case, the Tamil Tiger-affiliated group was able to beam its programming without Intelsat’s knowledge for an undetermined period of time.

Spector said that in mid-March, Intelsat received a letter from the Sri Lankan government seeking an explanation of the Tamil Tiger broadcasts.

Intelsat officials met in Washington April 10 with Sri Lanka’s ambassador to the United States , Bernard Goonetilleke, to discuss the issue and to outline steps the company is taking to stop the illegal broadcasts.

In a statement issued after the meeting and made public April 11 by Intelsat, Goonetilleke said he is “satisfied that Intelsat is taking these unauthorized transmissions very seriously, and believe it would do all that it can to stop the terrorist transmissions.”

Spector declined to discuss the means available to Intelsat to stop the transmissions and prevent a recurrence on another vacant transponder. He also declined to say whether Intelsat has identified the geographic location of the Earth station being used.

But one industry official said Intelsat has decided to transfer existing customers using the beam to another beam or another satellite with similar coverage, and then to aim the beam elsewhere so that it does not cover Sri Lanka.

Intelsat has a legal right to switch customers from beam to beam, or from one satellite to another, on 30 days’ notice so long as the customers are still able to access the desired market with the same frequency and power. But Intelsat in this case has sought permission to make the switch immediately. One of the two customers on the beam has agreed. Eutelsat has not.

For reasons that are not clear, Eutelsat has invoked the contract’s terms to require that the 30-day notice be respected.

“This should be an industry-wide concern,” this official said. “Eutelsat may be worried that Intelsat will use the beam in question to open up new business in the region in competition to Eutelsat. But here we’re talking about a terrorist organization and we all have the same interest in denying these people access, and all Eutelsat is gaining is 30 days.”

Eutelsat spokeswoman Vanessa O’Connor said the company would have no comment on the situation.

The origin of the Tamil Tigers’ movement is in Sri Lanka’s Tamil ethnic minority. The same ethnic group is found in India’s Tamil Nadu state, in southeast India. Sri Lankan authorities in the past have said the Tigers find much of their outside support in Tamil Nadu, as well as in the Tamil diaspora in Asia, Europe and North America.