May 1, 2026
Before the
FEDERAL COMMUNICATIONS COMMISSION
Washington, D.C. 20554
In the Matter Of Unleashing American Drone Dominance (GN Docket No. 26-74; WT Docket No. 22-323; WT Docket No. 24-629)
COMMENTS OF THE AMERICAN ASTRONOMICAL SOCIETY
The American Astronomical Society (AAS), the major organization of professional astronomers in the United States representing over 8,500 members, appreciates the opportunity to provide comments in response to this Public Notice.
On April 1, 2026, the Federal Communications Commission released a Public Notice (DA 26-314) seeking comment on expanding flexible use of spectrum to support Uncrewed Aircraft Systems (UAS). The notice requests input on the use of multiple frequency bands for UAS command-and-control and other communications, as well as on potential regulatory changes affecting these operations.
The AAS submits these comments to highlight considerations related to the protection of passive scientific services, particularly the Radio Astronomy Service (RAS).
I. Introduction
UAS platforms represent a fundamentally different class of spectrum users compared to ground-based systems due to their altitude, mobility, and expected deployment scale. These characteristics increase the likelihood of line-of-sight propagation over large distances and reduce the natural shielding effects that typically limit interference from ground-based systems. As a result, even low-power emissions may contribute to aggregate interference affecting sensitive receivers.
The RAS passively operates at extremely low signal levels and is particularly vulnerable to such interference. While many of the frequency bands identified in the Public Notice do not directly overlap RAS allocations, we want to bring attention to several bands that are adjacent to or capable of producing emissions within protected bands. It is critical to the preservation of radio astronomy that these factors be considered in the Commission’s evaluation.
II. Impacted Radio Astronomy Bands
Several of the bands under consideration raise concerns due to their proximity to RAS allocations or the potential for harmonic emissions into protected frequencies. Bands for UAS use that may pose a risk to RAS operations include:
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1432-1435 MHz: This band only has 5 MHz separation from the 1400-1427 MHz RAS primary allocation, within which all emissions are prohibited under US246 and RR 5.340. Depending on UAS transmission power levels, this 5 MHz separation may not be sufficient to prevent leakage into the protected 1400-1427 MHz band.
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1670-1675 MHz: This band is adjacent to the 1668.4-1670 MHz RAS primary allocation, for which all practicable steps must be taken to prevent harmful interference under US342. For the 1670-1690 MHz band, US211 urges applicants for airborne assignments to take all practicable steps to protect RAS in adjacent bands.
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2400-2500 MHz: The second harmonic emissions of this band fall in the RAS primary allocation 4990-5000 MHz, within which all emissions are prohibited under US246.
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5000-5725 MHz: This wide band is adjacent to the 4990-5000 MHz RAS primary allocation, within which all emissions are prohibited under US246.
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24.45-24.65 GHz: The second harmonic emissions of this band fall in the 48.94-49.04 GHz band, within which all emissions from airborne stations are prohibited under RR 5.340.
Out-of-band and harmonic emissions are a serious concern for sensitive RAS receivers, particularly in the context of large-scale deployment of airborne devices like UAS with varied emission characteristics. The Commission should therefore ensure that stringent emission limits and harmonic suppression requirements are applied to UAS systems, consistent with domestic and international rules.
III. Operational Considerations and Coordination
UAS communications, particularly command-and-control links, are typically local in nature, suggesting that wide-area, high-power transmissions are not required for effective organization. This attribute creates an opportunity to implement targeted mitigation strategies that reduce interference risk without limiting functionality. These measures could include geographical coordination, dynamic spectrum sharing, and exclusion zones, as well as the consideration of power and operational constraints in radio sensitive regions. Given the unique propagation characteristics of airborne systems, these approaches represent practical methods for maintaining compatibility with passive RAS activities.
IV. Consideration of Intentional Interference
The Public Notice seeks comment on potential reforms related to counter-UAS operations, including the permissibility of intentional interference under Section 333 of the Communications Act. The AAS urges caution in this area, as intentional interference could be uncontrolled and unpredictable, extending beyond intended targets and affecting adjacent or harmonic frequency bands. These risks are particularly significant for passive services including the RAS that depend on extremely low noise environments. Any changes to existing policy should ensure that the longstanding principle of minimizing harmful interference is preserved and that impacts on passive spectrum users are fully considered.
V. Concluding remarks
The expansion of UAS capabilities presents important opportunities but also introduces new considerations for spectrum management due to the airborne and distributed nature of these systems. Operations in bands that do not directly overlap protected allocations still risk adjacent-band and harmonic impacts, and the aggregate effects of proliferated deployments enhance interference risks. We request that the Commission support UAS innovation while ensuring continued compatibility with critical scientific services by explicitly applying existing protections, maintaining strong emission controls, and considering the unique characteristics of UAS operations.
Thank you for your consideration.
On behalf of the American Astronomical Society,
Dara Norman, PhD
President, American Astronomical Society