Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Agenda Items at Issue at the World Radiocommunication Conference 2023 (2022) / Chapter Skim
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1 Introduction
1 Introduction
Pages 1-16
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In remote sensing, these frequency bands are dictated by the electromagnetic properties of Earth parameters, including atmospheric temperature, humidity, cloud particles and precipitation, and composition; sea-surface temperature, heights, winds, and salinity; soil moisture and vegetation health; and cryosphere NOTE: This Introduction is an updated version of National Academies of Sciences, Engineering, and Medicine, Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Agenda Items of Interest to the Science Services at the World Radiocommunication Conference 2019, The National Academies Press, Washington, D.C., 2017.
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uses receivers to measure natural radio frequency emissions from the oceans, land, and atmosphere (including severe weather phenomena such as tropical storms)
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For EESS, temporal coordination based on satellite ephemerides may be an effective approach to sharing the radio spectrum. However, active transmitters that are airborne are potential sources of radio frequency interference for both groundbased and spaceborne receivers, depending on their power level, antenna radiation pattern, polarization, distance, and other parameters.
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Every country is sovereign to allocate uses of the radio frequency spectrum within its borders, but most choose to follow the International Table of Frequency Allocations out of convenience and to avoid potential interference to their neighbors. Every 2 to 5 years, the ITU convenes a World Radiocommunication Conference (WRC)
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agencies dealing with radio spectrum issues, other Administrations and foreign scientific users may find its recommendations useful in their own WRC planning. This report identifies the WRC-23 agenda items of relevance to U.S.
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in the mobile service in certain frequency bands below 2.7 GHz already identified for IMT, on a global or regional level; 1.5 To review the spectrum use and spectrum needs of existing services in the frequency band 470-960 MHz in Region 1 and consider possible regulatory actions in the frequency band 470-694 MHz in Region 1 on the basis of the review in accordance with Resolution 235 (WRC-15) ; 1.8 To consider, on the basis of ITU-R studies in accordance with Resolution 171 (WRC-19)
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by Earth stations on aircraft and vessels communicating with geostationary space stations in the fixed satellite service globally, in accordance with Resolution 172 (WRC-19) ; 1.16 To study and develop technical, operational, and regulatory measures, as appropriate, to facilitate the use of the frequency bands 17.7-18.6 GHz and 18.8-19.3 GHz and 19.7-20.2 GHz (space-to-Earth)
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TABLE 1.2 Preliminary WRC-27 Agenda Items Relevant to RAS and EESS WRC-27 a 2 On the basis of proposals from administrations and the Report of the Conference Preparatory Meeting, and taking account of the results of WRC-23, to consider and take appropriate action in respect of the following items: 2.1 To consider, in accordance with Resolution 663 (WRC-19) , additional spectrum allocations to the radiolocation service on a co-primary basis in the frequency band 231.5-275 GHz and identification for radiolocation applications in frequency bands in the range 275-700 GHz for millimetre and sub-millimetre wave imaging systems; 2.2 To study and develop technical, operational, and regulatory measures, as appropriate, to facilitate the use of the frequency bands 37.5-39.5 GHz (space-to-Earth)
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; 2.5 The conditions for the use of the 71-76 GHz and 81-86 GHz frequency bands by stations in the satellite services to ensure compatibility with passive services in accordance with Resolution 776 (WRC-19) ; 2.6 To consider regulatory provisions for appropriate recognition of space weather sensors and their protection in the Radio Regulations, taking into account the results of ITU-R studies reported to WRC-23 under agenda item 9.1 and its corresponding Resolution 657 (Rev.
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A more complete view of both the scientific uses and the frequency allocations in the radio spectrum can be found in Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses: Second Edition.4 EARTH EXPLORATION-SATELLITE SERVICE Satellite remote sensing is a uniquely valuable resource for monitoring the global atmosphere, land, and oceans. Microwave remote sensing from space presents a global view, vital for obtaining atmospheric and surface data for the entire planet, particularly when optical remote sensing is blocked by clouds or attenuated by water vapor.
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Measurement precision and accuracy is already limited by the available bandwidth, and some of these valuable measurements are being blocked by radio frequency interference, even within protected bands. For instance, it is now impossible to retrieve soil moisture from measurements made by the Advanced Microwave Scanning Radiometer (AMSR2)
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This is not true at optical frequencies, where many objects and phenomena are unobservable due to the absorption of pervasive interstellar dust. For example, the deep interiors of molecular clouds, places where new stars are forming, are completely cloaked by interstellar dust, yet transparent to radio emission.
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Subsequent radio observations of pulsars have revolutionized understanding of the physics of neutron stars and have resulted in the first experimental evidence for gravita tional radiation, which was recognized with the awarding of another Nobel Prize. Recently, radio astronomy was used to detect the first electromagnetic signal from merging compact objects identified by their gravitational waves and to provide the first ever image of the accretion disk around a supermassive black hole.
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Techniques developed for high spatial resolution imaging of celestial radio sources are used to determine Earth Orientation Parameters (EOP) , which describe anomalies in the rotation of Earth due to the changing of distribution of Earth's mass over time.
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As mentioned above, radio observations of spectral lines require measurements at frequencies determined by the physical and chemical properties of individual atoms and molecules. In particular, knowledge of the chemical makeup of the universe comes through measurements of spectral lines arising from atomic and molecular transitions, so it is important to protect radio astronomers' access to the characteristic frequencies of the most important atomic and molecular transitions, including sufficient bandwidth to measure spectral lines broadened by both thermal and kinematic processes.
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Thus, it is clear that all users, both passive and active, benefit from a clean spectrum. In other words, while radio astronomy facilities rely in part on geographic shielding and local designations of radio quiet zones to reduce sources of RFI, it is the shared responsibility of all users to assure effective use of the radio spectrum and to enable both active and passive services to co-exist.
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