Frequency Coordination and Interference Prevention in Starlink Satellite Operations

In a significant effort to balance the expansion of high-speed internet services with the protection of radio astronomy, the National Science Foundation (NSF) and SpaceX have been engaged in a comprehensive coordination agreement to mitigate interference from SpaceX's Starlink satellite network.

Historical Context and Initial Agreement

The collaboration between NSF and SpaceX began in 2019, when the two entities finalized a coordination agreement aimed at ensuring that the Starlink satellite network complies with international radio astronomy protection standards, particularly in the 10.6 – 10.7 GHz radio astronomy band. This agreement was a crucial step in fulfilling the conditions of SpaceX's Generation 1 Federal Communications Commission (FCC) license[1][4].

Ongoing Efforts and Enhanced Coordination

Building on the initial agreement, NSF and SpaceX signed a new coordination agreement in 2022 to further protect ground-based astronomy. This agreement includes several key provisions:

Dynamic Coordination for Radio Astronomy: SpaceX has committed to dynamically coordinating with impacted U.S. radio astronomy facilities to avoid main beam illumination during observations. This commitment extends beyond the required international protections for the 10.6-10.7 GHz band, enabling radio astronomy observations in other bands not allocated to radio astronomy. Key facilities such as the Very Large Array (VLA), Very Long Baseline Array (VLBA), Green Bank Observatory (GBO), and geodetic Very Long Baseline Interferometric (VLBI) stations are included in this coordination[1][4].
Field Tests and Verification: Field tests have been conducted at the VLA and GBO to verify that radio astronomy observations are not impacted by Starlink satellites. Additional tests are planned to continue monitoring the level of impact in various frequency ranges, including 10.7-12.27 GHz and 14.0-14.5 GHz[1][4].
Adaptive Optics and Laser Clearinghouse: SpaceX has analyzed the impact of astronomical facility lasers on its satellites, leading to the removal of coordination requirements for these lasers by the Laser Clearinghouse. This change allows adaptive optics lasers at ground-based facilities to operate without multiple closures every time SpaceX satellites pass nearby. A workshop is also being organized by SpaceX and NSF’s NOIRLab to develop best practices for interactions between satellite operators and the Laser Clearinghouse[1].

Polar Regions and Remote Sites: SpaceX has committed to working with NSF’s Office of Polar Programs to minimize the impact on remote geographical radio astronomy sites in polar regions when providing data connectivity in these areas[1].

Technical and Regulatory Aspects

The Starlink satellite constellation operates in several frequency bands, which can potentially interfere with radio astronomy observations. For instance, radiation associated with Starlink satellites has been detected at frequencies between 110 and 188 MHz, well below the allocated radio transmission downlinks in the 10.7–12.7 GHz band. These unintended electromagnetic radiations (UEMR) have been observed using the LOFAR radio telescope and indicate possible differences in the operational state or hardware of the satellites[3].

FCC Licensing and Frequency Allocations

SpaceX has been working through various FCC licensing processes to expand its operational frequencies. Recently, the FCC authorized SpaceX to deploy a modified version of its Gen2 Starlink satellites, allowing them to operate in certain frequencies within the 1429 MHz to 2690 MHz range. SpaceX also seeks to conduct commercial Satellite Communication Services (SCS) operations in the 1910-1915 MHz and 1990-1995 MHz frequency bands, although these requests remain pending[2].

Collaboration and Future Directions

The collaboration between NSF and SpaceX is seen as a model for future cooperation between commercial satellite providers and research facilities. NSF Director Sethuraman Panchanathan emphasized the importance of this partnership in allowing science research to flourish alongside satellite communication. Tony Beasley, NRAO Director, highlighted that cooperation between these entities is essential for ensuring the future of both industries, which rely on the limited radio spectrum[1][4].

NSF’s NOIRLab and NRAO continue to serve as key points of contact for technical exchanges with SpaceX on optical, infrared, and radio astronomy issues. The ongoing efforts include a pilot program by NSF’s NRAO to test the impact of SpaceX user terminals in close proximity to the VLA, reflecting the commitment to addressing new challenges as they arise[1].

As the Starlink constellation continues to expand, with over 3,000 satellites currently in orbit, the need for robust coordination and interference prevention measures remains paramount to safeguarding radio astronomy observations while supporting the growth of commercial satellite services.