From Interference to Orbits, NGSO Plans Raising Numerous Questions, Concerns

Several satellite operators repeated their concerns about multiple NGSO proposals. Telesat Canada petitioned to deny multiple NGSO applications (for example, here), citing overlapping geographies and Ka-band frequencies. SpaceX, in multiple comments on different proposed NGSO constellations, said (for example, here) large coverage areas will make NGSO spectrum sharing far more complicated, and those other NGSOs' uplinks likely will cause significant interference to low earth orbit (LEO) satellites, forcing default band segmentation. Space Norway more than once (for example, here) said the FCC should require medium earth orbit (MEO) NGSO constellations to take steps to avoid in-line interference with highly elliptical orbit NGSO systems with only one active satellite, such as equivalent power flux-density (EPFD) limits.

Each of the NGSO applicants needs to demonstrate how it would protect GSO networks, SES and O3b said, saying the FCC should make clear the obligation future NGSO systems have to share spectrum with co-frequency NGSO operations. They said the FCC should defer consideration of requests for relief from system construction and operation milestones. They said any authorizations need to include terms and conditions consistent with those imposed on other operators.

The proposed NGSO operations shouldn't pose any harm to existing and future GSO operations as long as those NGSOs are limited to the parameters specified in the applications, ViaSat said. It said approvals should be conditioned on results of pending Part 2 and Part 25 rules updates and on NGSO operators being responsible for immediately implementing any technical or operational changes needed to protect GSO operations.

NGSO applicants cited interference worries regarding O3b. SpaceX said the FCC should ensure all systems at all altitudes under consideration in the processing round can coexist, and impose license conditions if necessary to make that happen. Telesat Canada said the band segmentation O3b recommends in such in-line interference events would be "unworkable" and that, at minimum, O3b approval should be conditioned on the outcome of the agency's current Part 2 and Part 25 satellite rules update.

Pointing to the planned orbit of Telesat Canada's constellation -- 1,000 kilometers to 1,248 kilometers -- and its overlap with OneWeb's planned 1,200-km altitude, OneWeb said Telesat should maintain a 125-km buffer zone between its constellation and others. It said Telesat needs to provide more data so orbital debris risk can be better assessed.

No FCC approval of Theia Holdings can come before it removes its proposed use of 1215-1300 MHz downlinks, the GPS Innovation Alliance said. It said Theia's synthetic aperture radar transmissions in that band -- used to get worldwide soil and vegetation information -- would create widespread interference for global navigation satellite system receivers. NASA said Theia's 120-satellite constellation would be in a relatively high-risk orbital area due to the amount of space debris at 800 kilometers, and the company should talk soon with it or the military about orbit altitude choice. NASA said there's no international consensus on minimum reliability of a satellite, though a pair of studies underway by it and the international Inter-Agency Space Debris Coordination Committee might help give answers to best practices for large satellite constellations. In the meantime, NASA said, companies such as SpaceX proposing large constellations need to be able to deal with "random failures" so they don't pose a threat to the International Space Station or other U.S. assets. The agency said SpaceX should "seek out creative ways" to ensure it avoids the ISS when deorbiting its satellites.

Without better information about how the NGSO constellations will comply with ITU EPFD limits, it's impossible to determine what kind of harmful interference potentials the constellations pose, Hughes Network said. It raised red flags about ViaSat's plans to use part of the Ka-band for inter-satellite links, saying the FCC should put off consideration of that part of ViaSat's application until there are appropriate technical and operational rules for MSO-to-GSO links.

Others also raised concerns about ViaSat's plans. OneWeb said the FCC should defer ViaSat's request to use Ka-band inter-satellite links until it submits an analysis for review. And Inmarsat pushed the FCC to deny the inter-satellite links request, saying ViaSat hasn't shown these proposed operations will be compatible with GSO FSS networks. Iridium also took aim at inter-satellite links in its petition to deny Audacy's application, saying Audacy apparently is unable to coordinate its inter-satellite links with Iridium's, especially since both networks would provide global coverage.

OneWeb pushed for the FCC to deny SpaceX's request for a partial waiver of the milestone requirement and a waiver of the domestic coverage requirement and to require the company to provide additional information showing its constellation won't be a significant source of orbital debris. OneWeb said it had concerns that SpaceX's requested waiver of downlink power flux density limits could end up causing terrestrial interference. Before approval, LeoSat, SpaceX, Space Norway, Telesat Canada and Theia Holdings first need to give more detail on their post-mission disposal plans, including how they will coordinate with users of the 400-650 km orbits such as Spire, that company said. It said the agency should condition Theia approval on it coordinating its use of the 1215-1300 MHz band with Spire.

With Boeing's proposed constellation using 19.3-19.7 GHz spectrum for downlinks and 29.1-29.5 GHz for uplinks -- spectrum that Iridium currently uses -- Iridium said Boeing approval should be conditioned on coordination with it.