Executive Summary

This report of the Committee on the Views on the World Radiocommunication Conference 2027 is primarily intended as a resource for those involved in the 2027 World Radiocommunication Conference (WRC-27) and/or those involved in preparatory meetings and studies for that conference. The report discusses how each of the various WRC-27 agenda items,¹ which consider potential changes to the international Radio Regulations (RR), may have a bearing on scientific use of the radio spectrum for radio astronomy and Earth observation. The report also considers, in more abbreviated form, preliminary agenda items for the subsequent WRC-31 conference.²

Measurements in the radiofrequency range of the electromagnetic spectrum provide a wealth of unique information on (1) the state of the Earth system and processes controlling its evolution on timescales from minutes to decades and (2) astrophysical phenomena from our own solar system to the furthest reaches of the universe and thus the earliest observable times. Much of the information gleaned cannot be obtained by any other measurement technique. However, these critical measurements, particularly the “passive” observation of natural emissions (essentially all of radio astronomy and much of Earth observation), involve quantification

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¹ See “Resolution 813 (WRC-23) Agenda for the 2027 World Radiocommunication Conference” in International Telecommunication Union (ITU), 2023, World Radiocommunication Conference 2023 (WRC-23) Final Acts, http://handle.itu.int/11.1002/pub/8225d4fb-en.

² See “Resolution 814 (WRC-23) Preliminary Agenda for the 2031 World Radiocommunication Conference” in ITU, 2023, World Radiocommunication Conference 2023 (WRC-23) Final Acts.

of very small signals. Furthermore, the scientific information typically derives from small changes in these signals. These signals and their variations would be completely drowned out by emissions from broadcasting, communications, and so on were it not for steps routinely taken to protect the scientific observations. These steps include ensuring spectral partitioning and/or geographical separation/shielding. As technologies advance, moving to higher and higher frequencies, placing cutting-edge communication devices in the hands of more and more users worldwide, and filling the skies with an increasing number of satellites, the potential for increased interference into scientific observations grows. Thus, great care is needed when updating the radio regulations to ensure that critical measures of our planet, solar system, galaxy, and universe can continue and, ideally, thrive.

The report captures the perspectives of the U.S. scientific community through its expert committee. Many committee members serve on the Committee on Radio Frequencies (CORF), whose main role is to track major radio spectrum issues facing the radio astronomy and Earth remote sensing communities. The committee membership also includes individuals participating in U.S. and international meetings related to spectrum usage, including “working parties” for the International Telecommunication Union (ITU). With this breadth and depth of perspectives, the committee was able to meet on several occasions over 6 months to discuss its viewpoints and articulate appropriate recommendations.

The core content of this report can be found in its discussions of the WRC agenda items. Each agenda item stands alone and lives its own life in the ITU process that the report is addressing. In essence, this report is a collection of mini-reports with recommendations pertaining to individual agenda items.

When taken as a whole, several common conclusions emerge. For radio astronomy, the committee has serious concerns surrounding the need to ensure protection of radio astronomy observations by means beyond frequency-based allocations and corresponding prohibitions on transmissions. Making cutting-edge observations of a host of celestial phenomena requires access to large bandwidths to maximize sensitivity and to accommodate cosmological redshift. Continued advances in astrophysics will only be possible through interference-free access to a large fraction of the radio spectrum.

For Earth remote sensing, recognizing the myriad societal benefits that accrue from incisive, robust, and timely observations of the Earth system, the committee underscores the importance of continued protection of such measurements. Specifically, the com-

mittee urges that decisions made regarding limits such as on out-of-band emissions for active services are consistent with protection of remote sensing, including consideration of aggregate emissions. Furthermore, the committee anticipates that, as Earth system science advances, demands for more frequent (ultimately near-continuous) observations will grow. This argues against the viability of “time-sharing” approaches to protection of remote sensing measurements in bands where Earth observation shares an allocation with other services.

As technologies for optical communication improve, it is hoped that increased adoption of these technologies (e.g., for communication to, from, and between orbiting spacecraft) will be used to relieve some of the pressure on active uses of the radio spectrum, benefiting passive scientific uses as well.

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