AAS comment on proposed “Satellite Spectrum Abundance” (FCC Docket 25-180)

The American Astronomical Society (AAS) appreciates the opportunity to comment on this Further Notice of Proposed Rulemaking (FNPRM) and Notice of Proposed Rulemaking (NPRM) seeking to make additional spectrum resources available for satellite communications, including select frequency bands ranging from 12.7 to 114.25 GHz.

The AAS is the primary professional organization for astronomers and astrophysicists in the United States. Currently, the AAS has more than 8,000 members, publishes premier astronomy journals, organizes meetings attended by thousands of its members, and represents the voice of astronomy to all. This comment was developed by the AAS Committee for Protection of Astronomy and the Space Environment (COMPASSE), which is a volunteer committee of professional astronomers and disciplinary experts established by AAS in 1988 to address issues related to the protection of dark and radio-quiet skies, the safe and sustainable use of outer space, and effective advocacy for the protection of U.S. astronomy.

On behalf of the United States astronomical community, we emphasize that frequency bands allocated to the Radio Astronomy Service (RAS) both domestically and internationally must be protected in accordance with the applicable International Radio Regulations, and therefore excluded from consideration for repurposing. We provide as an annex to these comments a list of the relevant frequency bands impacted by this FNPRM/NPRM that are allocated to the RAS on a primary or secondary basis, as well as those for which all practicable steps to protect the RAS are urged in accordance with the footnotes to the United States Table of Frequency Allocations (47 CFR § 2.105) and the International Telecommunication Union Radiocommunication Sector Radio Regulations (ITU-R RR). 

The bands allocated to the RAS are often shared by different types of scientific investigations on Earth and in space, making them some of the most efficiently utilized in the entire radio spectrum. These other scientific uses include weather and atmospheric monitoring, which have direct impacts on weather forecasting and protecting lives and property from natural hazards. Additionally, Very Long Baseline Interferometry (VLBI) is a type of radio astronomy observation used for geodesy to calibrate the Global Positioning System (GPS) that is coordinated worldwide through the International VLBI Service for Geodesy and Astrometry (IVS). U.S. VLBI systems include several stations of the VLBI Global Observing System (VGOS) operated by NASA and the Very Long Baseline Array (VLBA) operated by the National Radio Astronomy Observatory (NRAO) on behalf of NSF. Report ITU-R RA.25071 describes the capabilities of global VGOS systems, including planned use of the 12.89–13.85 GHz range, which is co-channel with the 12.75–13.25 GHz band considered for repurposing in this FNPRM/NPRM. We note the importance of accurate GPS calibration for numerous life-critical and national-security related operations in the United States and abroad, and request that the Commission work with relevant entities to ensure non-interference with VLBI systems (including the VLBA and VGOS) as this process continues.

Spectrum allocations to science services are based on the frequencies at which we can observe specific natural phenomena; these frequencies are governed by the laws of physics, and thus many of the observations critical for elucidating those phenomena cannot be carried out in other bands.2 As such, the ITU-R has recognized the importance of these bands for advancing human knowledge and allocated them worldwide to the RAS and other passive science services, with associated specific protection criteria (see, e.g., Recommendation ITU-R RA.7693). Reallocating frequency bands that have long been used globally for passive services to active satellite services would risk disrupting scientific research at U.S.-funded facilities in the United States and (once a new precedent is set) elsewhere, including Mexico, which will host part of the U.S.-funded Next Generation Very Large Array (ngVLA), and Chile, where the U.S.- funded Atacama Large Millimeter/submillimeter Array (ALMA) is located. We note that the ITU-R RR is a binding treaty under the auspices of the United Nations onto which the United States has signed, and which the United States is therefore responsible for upholding.

The AAS would also like to encourage the Commission to consider the comments provided by NRAO in
concert with the Green Bank Observatory (GBO) on this FNPRM/NPRM. As the operator of the preeminent U.S. radio astronomy facilities that observe in the bands being considered for repurposing,
NRAO has provided in its comments detailed analysis of the present use of these bands and the
challenges that would be created by reallocation to satellite services, as well as recommendations for
needed steps to be taken to protect radio astronomy. In addition to noting the bands allocated to the RAS listed in the attached annex, we kindly request that the Commission carefully review the comments submitted by NRAO for expanded context on the practical importance of protecting these bands. Furthermore, the Committee on Radio Frequencies of the National Academies of Sciences, Engineering and Medicine (NASEM CORF) recently published its Views on the World Radiocommunication Conference 20274, which provides specific recommendations for radio astronomy and remote sensing sciences on radio spectrum issues currently under consideration in the ITU-R; we direct the Commission towards this valuable resource as well.

The American Astronomical Society strongly encourages the Commission to add new coordination
zones around radio astronomy stations and to add other technical rules, as required, as part of any
final rulemaking that approves repurposing. It is critical to ensure Recommendation ITU-R RA.769
levels can be met and that radio astronomy observations may continue leading to new discoveries. Even if repurposing does not occur in the bands allocated to the RAS, we continue to observe the universe at all radio frequencies. The establishment of small coordination zones around U.S. radio astronomy facilities would allow these fundamental scientific observations to proceed with minimal impact on commercial operations. 

Respectfully submitted by:
Dara Norman, PhD
President, American Astronomical Society