Low Earth Orbit Constellations Could Pose Interference Risk to GEO Satellites

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WASHINGTON — A proposed wave of low Earth orbit communications satellite constellations could become an interference hazard for satellites in geostationary orbit even if those new systems comply with existing rules, some satellite operators fear.

Rules enacted by the International Telecommunication Union (ITU) in 2000, during the previous wave of proposed nongeostationary orbit (NGSO) satellite systems, gives frequency priority to satellites in geostationary orbit. NGSO systems must take measures, such as reducing their power output, to avoid interfering with geostationary satellites.

The problem, said company representatives attending the fourth annual Space and Satellite Regulatory Colloquium here Oct. 22, is that advances in geostationary satellites allow them to operate at lower power levels. That creates the potential for interference with NGSO systems, even if they are in compliance with ITU rules.

“As we’re moving to the new higher-capacity satellites and technology has improved, the sensitivity of our satellites is quite a bit higher than what was envisioned back in the day,” said Daryl Hunter, senior director of regulatory affairs for ViaSat, a company that operates high-throughput satellites in geostationary orbit.

“Even when these new NGSO constellations meet the equivalent power flux density limits that were established by the ITU, they actually cause interference to the new high-capacity GSO satellites,” he said. “But we have to live with it. That’s the law.”

Hunter said that problem could be exacerbated if a number of the proposed NGSO satellite systems are launched over the next several years. If some of them violate the ITU rules, he said, it could be difficult to determine which ones are causing the excess interference.

“Who’s doing the interference? All we know is that our noise floor is raised,” he said. “It’s really going to be a tough problem.”

Hunter and others at the meeting, though, said they were not pressing for near-term changes to the rules that could require NGSO systems to further reduce their power to avoid interference, since it was not clear how serious any interference would be. “We haven’t made a proposal yet to go back and revisit them,” he said of the current rules.

“We’re really cautioning against any rapid changes that could have some drastic consequences,” said Mariah Shuman, regulatory counsel for O3b Networks, which operates a constellation of NGSO satellites. That includes taking no action on the issue at November’s World Radiocommunication Conference, known as WRC-15, in Geneva.

“We support studies at this point,” she said of the interference issue. “We would not want to see any decisions made at WRC-15.”

“Pulling the rug from underneath the NGSO operators at this point — prematurely, I think — will actually hurt the industry in general,” said Hazem Moakkit, vice president for corporate and spectrum strategy at Intelsat, which both operates a fleet of geostationary satellites and has a stake in NGSO satellite company OneWeb. “It’s better to wait until we advance a little bit further.”

While industry is willing to wait on interference issues, some raised questions about another aspect of ITU rules regarding NGSO systems. Current regulations consider an NGSO system to be brought into use, and its frequency rights confirmed, when the first satellite of a constellation is launched, regardless of the number of satellites in the constellation.

“This makes sense when you have a constellation of 10 or 12 satellites,” said Jose Albuquerque, chief of the satellite division of the Federal Communication Commission’s International Bureau. “But when you’re talking about constellations of 800 or 4,000 satellites, you cannot acquire rights by bringing one satellite into service.”

Many of the concerns about NGSO systems discussed at the colloquium are based on the assumption that several of the systems under development now will actually be deployed. At least one attendee, though, has his doubts.

“We are probably on the back side of the bubble” of investment in the industry, said J. Armand Musey, president of Summit Ridge Group. “It’s not clear that there’s going to be a whole lot of OneWebs. There’s probably going to be one, maybe two, big LEO constellations that come out of this phase. There’s not going to be five of them.”