Radio Astronomy Interests Say They Face Possible 'Existential Threat' From SCS
Don't expect traditional methods of protecting radio astronomy from spectral interference to work when it comes to supplemental coverage from space (SCS), according to radio astronomy interests. In comments last week (docket 23-65), radio astronomy advocates repeatedly warned that SCS service poses a significant interference risk. Multiple parties said SCS service is too new to justify emergency calling requirements. The FCC's SCS framework order adopted in March (see 2403140050) included a Further NPRM on 911 and radio astronomy issues.
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"Radio astronomy now faces a potential existential threat from SCS," Canada's Outer Space Institute said. Existing protections "will no longer be possible with persistent interference from overhead satellite transmissions and orbital electronics noise," OSI said. It urged continuing to require coordination between satellite operators and the National Science Foundation and enforcing power flux density requirements for cellular usage within the National Radio Quiet Zone. The American Astronomical Society's Committee for the Protection of Astronomy and the Space Environment also said SCS poses "a serious threat" to radio astronomy. COMPASSE said operators should "clearly demonstrate" during the licensing process that they won't cause harmful interference with radio astronomy. Even if SCS operators limit transmissions when passing over radio quiet zones and observatories, the terrestrial mobile bands they use result in "messier spatial beams" that can leak into radio quiet zones and observation sites, it said. COMPASSE called on the FCC to extend radio quiet zone protections to include interference from above.
Radio astronomy research can't be done without access to interference-free spectrum bands and protected geographic locations, said the National Academy of Sciences' Committee on Radio Frequencies. It said that while the earth's curvature or terrain protects radio astronomy operations from distant terrestrial networks, that doesn't happen when thousands of transmitters are in orbit supporting SCS. It urged the FCC to take an approach where each SCS proposal has initial trial avoidance parameters that could be refined over time to try to minimize interference.
SCS constellations, with their large antennas, also could cause visual interference with optical astronomy, DarkSky International said. It called on the FCC to require that operators mitigate visual brightness. Pointing to possible environmental effects from SCS satellites burning up in the atmosphere on reentry, it said the FCC should analyze those possible effects in an environmental impact statement, or at least document the absence of significant environmental impacts in an environmental assessment. The International Astronomical Union also urged protections for radio and optical astronomy. NTIA submitted suggested methodology for analyzing the impact on a radio astronomy observatory, including the model for calculating excursion zones needed to protect astronomy.
More protections for radio astronomy operations would ignore the existing spectrum usage rights of terrestrial wireless providers, CTIA said. That could delay deployments in remote areas, it added. SpaceX said the FCC can best protect radio astronomy activities by requiring that SCS operators coordinate with the National Science Foundation before starting operations in the U.S. AT&T said SCS-specific rules for radio astronomy coordination are premature, as are 911 rules for SCS service.
CTIA also said it was too soon to adopt routing or location accuracy requirements for 911 calls and tests, as SCS providers are focused on introducing emergency connectivity to many areas. Intrado, SpaceX, T-Mobile and AT&T made similar statements.
Location-based routing is probably the quickest way of getting an SCS 911 call or text to the appropriate emergency communications center, and the FCC should require that treatment of SCS 911 calls, the Association of Public-Safety Communications Officials said.
SpaceX urged the FCC to reconsider the aggregate out-of-band power flux density limit it adopted in the SCS order. In a reconsideration petition, it said the agency instead should opt for band-specific out-of-band PFD limits. It said it plans to commence commercial SCS service this fall.