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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2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-23 and WRC-27 Agenda Items
2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-23 and WRC-27 Agenda Items
Pages 17-104
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in 2023 and preliminary agenda items for WRC-27.
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Of primary consideration for the science services regarding this agenda item are the frequency bands listed in Radio Regulation (RR)
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. In addition, footnote RR 5.458A urges administrations to take all practicable steps to protect spectral-line observations of the RAS in the band 6650-6675.2 MHz from harmful interference from unwanted emis sions of space stations of the fixed-satellite service.
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Earth Exploration-Satellite Service The radio regulations include direct reference to several of the bands under consideration in this agenda item. RR 5.458 states the following: In the band 6425-7075 MHz, passive microwave sensor measure ments are carried out over the oceans.
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(km) AMSR2 JAXA GCOM-W 6.925 V,H 350 36 × 62 AMSR2 JAXA GCOM-W 7.3 V,H 350 35 × 62 AMSR2 JAXA GCOM-W 10.65 V,H 100 24 × 42 WindSat DoD Coriolis 6.8 V,H 125 39 × 71 WindSat DoD Coriolis 10.7 V,H,3,4 300 25 × 38 GMI NASA GPM Core 10.65 V,H 100 19 × 32 MTVZA- RosHydroMet Meteor- 6.9 V,H 400 135 × 302 GY-MP MP N1/N2 MTVZA- RosHydroMet Meteor- 10.6 V,H 100 89 × 198 GY-MP MP N1/N2 MTVZA- RosHydroMet Meteor-M 10.6 V,H 100 89 × 108 GY N2-1/5 MWRI NSOAS HY-2A/B 6.6 V,H 350 80 × 120 MWRI NSOAS HY-2A/B 10.7 V,H 250 50 × 75 MWRI CMA FY3A-H 10.65 V,H 180 51 × 85 CIMR Copernicus 6.925 V,H,3,4 825 max.
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Recommendation: The committee recommends that if the 3300-3400 MHz, the 6425-7025 MHz, and/or the 7025-7125 MHz frequency bands are identified for International Mobile Tele communications (IMT) , the strongest possible protections be provided to the RAS for observations of the two CH lines in the 3332-3339 MHz and 3345.8-3352.5 MHz bands and to the methanol line in the 6650-6675.2 MHz band, all of which are included in RR 5.149.
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are outside the scope and there should be no additional regulatory or technical constraints imposed on the deployment of ground-based IMT systems in the frequency bands referred to in those footnotes." The footnotes in recognizing d) (listed above)
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Recommendation ITU-R RS.2017 lists a maximum interference level of −176 dBW in a 10 MHz bandwidth within the frequency band of 2.64-2.70 GHz for EESS sensors. For the frequency bands that are at risk from har monics of the 694-960 MHz band, the maximum interference level for EESS sensors from HIBS base stations is −182 dBW in 27 MHz for the 1.370-1.427 GHz band (ITU-R RS.2336)
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and into other frequency bands where RAS is co-primary, including frequency bands designed for observations of the OH emission line (1610.6-1613.8 MHz and 1660-1670 MHz, both of which are listed in RR 5.149, where administrations are urged to take all practicable steps to protect the radio astronomy service)
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are authorized to operate in the frequency bands listed in Reso lution 247 (WRC-19)
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considers "that it is necessary to adequately protect all primary services in the frequency band 470-694 MHz and in adjacent frequency bands"; furthermore, it states "that, in some countries, parts of the frequency band are also allocated to the radiolocation service on a secondary basis, limited to the operation of wind profiler radars (No.
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The committee notes that several major RAS facilities operate in this frequency range in Region 1, which includes the MeerKAT radio telescope in South Africa, the radio telescope in Effelsberg, Germany, and the Observation Radiospéctrale pour FEDOME et les Etudes des Eruptions Solaires (ORFEES) spectrograph at Nançay in France, the Lovell telescope in United Kingdom, and RATAN-600 in Zelenchukskaya, Russia.
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. Continued RAS use of the 608-614 MHz band in Region 1 (606-614 MHz in the African Broadcast Area)
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It states that "in order to protect the radio astronomy service in the frequency band 14.47-14.5 GHz, administrations operating UAS in accordance with this Resolution in the frequency band 14-14.47 GHz within line-ofsight of radio astronomy stations are urged to take all practicable steps to ensure that the emissions from the UA in the frequency band 14.47-14.5 GHz do not exceed the levels and percentage of data loss given in the most recent versions of Recommendations ITU-R RA.769 and ITU-R RA.1513." Additionally, RR 5.504B states that "Aircraft earth stations operating in the aeronautical mobile-satellite service in the band 14-14.5 GHz shall comply with the provisions of Annex 1, Part C of Recommendation ITU-R M.1643, with respect to any radio astronomy station performing observations in the 14.47-14.5 GHz band 3 May also be used consistent with international standards and practices approved by the responsible civil aviation authority.
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Of primary consideration for the science services is the adjacent frequency band 14.47-14.5 GHz listed in RR 5.149 and allocated on a secondary basis worldwide. RR 5.149 urges administrations to take all practicable steps to protect the RAS from harmful interference in a number of bands, including the 14.47-14.5 GHz band, when making assignments to other services to which the bands are allocated.
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32 WORLD RADIOCOMMUNICATION CONFERENCE 2023 ITU-R M.1643, should be adopted worldwide. The committee recommends the adoption of a footnote to the radio regulations that specifies such protections.
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Care should be taken according to Resolution 429 (WRC-19) that "any channel aggregation needs to be performed in a manner that protects other primary services operating in band and in adjacent frequency bands." This could be achieved by avoidance of digital broadcasting at the edge of the RAS allocation and institution of a guard band.
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Furthermore, in order to protect the RAS primary allocation from OOBEs, the committee recommends avoiding allocations to airborne systems adjacent to primary RAS bands, such as the 13.260-13.360 MHz band listed in Appendix 27, which is adja cent to the primary RAS band at 13.36-13.41 MHz.
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invites sharing and compatibility studies in the frequency bands 15.4-15.7 GHz and 22-22.21 GHz and the definition of appropriate protection levels for unwanted emissions into the adjacent bands allocated to the passive services. Of particular concern for the science services are the potential for increased transmissions at 22-22.21 GHz, where administrations are urged to take all practicable steps to protect the RAS (RR 5.149)
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This ability is essential for probing areas of star formation throughout the Milky Way and the universe. A number of important molecules also have transitions in frequency bands affected by this agenda item.
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The wealth of information derived from observations of these and other spectral lines provide insight into the formation, structure, and physical properties of molecular clouds in both the Milky Way and nearby galaxies. Radio telescopes that operate at these frequencies include, among others, HartRAO (South Africa)
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Thus, the current restriction "except aeronautical mobile" is well justified in these frequency bands. Recommendation: The committee recommends that the pro tection levels in Recommendations ITU-R RA.769 and ITU-R RS.2017 be adopted for sharing and compatibility studies asso ciated with Agenda Item 1.10, as no further definition of the appropriate protection levels from unwanted emissions into the adjacent passive services bands is necessary.
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Radio Astronomy Service As noted in 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, WRC-19 Agenda Item 1.8: The 1610.6-1613.8 MHz band is used for spectral line observations of the hydroxyl radical (OH)
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Observations in the 1612 MHz band and the 5 GHz band are carried out at a number of radio astronomy sites in numerous countries worldwide. In the United States, these include the Very Large Array, the Green Bank Telescope, the Arecibo Observatory,4 the Allen Telescope Array, and the 10 stations of the Very Long Baseline Array.
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VIEWS ON SELECTED WRC-23 AND WRC-27 AGENDA ITEMS 41 tent protection from both in-band and unwanted emissions. The RAS band 4990-5000 MHz must be protected from the second harmonics of transmissions in the 2483.5-2500 MHz band.
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on a secondary basis; that country footnotes to the Table of Frequency Allocations for the frequency range 40-50 MHz provide primary allocations for the aeronautical radionavigation and radiolocation services in certain parts of the world; that Recommendation ITU-R RS.2042-1 provides typical technical and operating characteristics for spaceborne radar sounder systems using the frequency range 40-50 MHz that should be used for interference and compatibility studies; [and] that Report ITU-R RS.2455-0 provides preliminary results of sharing studies between a 45 MHz radar sounder and incumbent fixed, mobile, broadcasting and space research services operating in the frequency range 40-50 MHz." Earth Exploration-Satellite Service Low-frequency radar is the only known method for collecting high-resolution observations of Earth's subsurface, such as root-zone soil moisture, water table in aquifers, and subsurface/multilayer ice deposits.
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According to the June 2019 ITU-R report, ITU-R RS.2455-0, the power flux density at Earth's surface beneath the satellite track is estimated at −93.3 dBW/m2 at the center frequency of 45 MHz, with a 3dB bandwidth of 8 MHz. Considering the antenna patterns and the geometry of observations, the radiated power outside of the primary MENA observation region will be less than −130 dBW.
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Planned compatibility studies should include consideration of the impacts of an orbiting 45 MHz radar sounder on radio telescope facilities operating in the bands listed above, with particular attention given to out-of-band and spurious emissions, including harmonics.
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This increased focus on this spectral region for radio astronomy observations has resulted in considerable interest in developing new radio astronomy observatories targeting these bands. Suitable coordination should allow for complete compatibility between an orbiting EESS (active)
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Under RR 5.340, no emission is allowed in the frequency range of 15.35-15.4 GHz, except those provided by RR 5.511, in which 15.35-15.4 GHz is also allocated to the fixed and mobile services on a secondary basis within a few specified countries. As noted above for Agenda Item 1.10, the frequency bands proposed for study in this agenda item are utilized for a range of both radio continuum and line observations.
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With a set of RRLs across a range of frequencies, it is also possible to determine the density of the medium from which they are emitted. Of particular concern are the ammonia line at 15.391 GHz, the carbon recombination line at 15.351 GHz, and the hydrogen recombination line at 15.360 GHz, which are included in the RASallocated band adjacent to the frequencies considered in this agenda item.
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." Agenda Item 1.14, and the resolution it cites, proposes a reassessment of the EESS (passive) assignments in the 231.5-252 GHz range, in light of plans to develop and launch new spaceborne instrumentation measuring in this region.
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Such ice clouds are an important and poorly understood aspect of the atmosphere system and represent a significant uncertainty on climate projections. A spaceborne sensor under development will provide measurements of ice cloud signatures in this spectral region and likely provides the motivation for this agenda item.
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Reflecting this scientific importance, the 1.3 mm band includes a number of existing RAS allocations. As noted above, there are RAS primary allocations at 241-248 GHz and 250-252 GHz, containing spectral lines of the molecules carbon sufide (CS)
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Adding EESS (passive) as co-primary to the existing RAS primary allocation at 241-248 GHz, and possibly expanding this allocation into adjacent bands, is an efficient way to support and protect new EESS (passive)
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." Accordingly, it invites ITU-R to "study the sharing and compatibility issues between Earth stations on aircraft and vessels communicating with GSO space stations in the FSS and current and planned stations of existing services referred to in considering c) as well as services in adjacent frequency bands, to ensure protection of, and not impose undue constraints on, those services and their future development, taking into account the provisions of Appendix 30B." Of particular concern for the scientific services is the potential for OOBEs into the adjacent EESS (active)
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Table 2.4 lists EESS (active) sensors measuring in the 13.25-13.75 GHz frequency bands.
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Recommendation: The committee urges that any sharing stud ies embarked upon under Agenda Item 1.15 explicitly consider the threshold limits in Recommendation ITU-R RS.1166-4 and recommend suitable out-of-band emission masks and/or guard bands to ensure they are met.
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to communicate with FSS space stations operating in the frequency bands" detailed above. The resolution resolves to invite the ITU to "study sharing and compatibility between ESIMs operating with non-GSO FSS systems and current and planned stations of primary services allocated in the frequency bands 17.7-18.6 GHz, 18.8-19.3 GHz and 19.7-20.2 GHz (space-to-Earth)
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Many of these sensors are used in operational weather forecasting systems to compute information on these parameters described above. Agenda Item 1.16 is examining the expanded use of the 17.7-18.6 GHz and 18.8-19.3 GHz bands for space-to-Earth links.
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Recommendation: The committee urges that any consideration of new or revised allocations to the 17.6-18.6 and 18.8-19.3 GHz bands explicitly consider the impact to the 18.6-18.8 GHz band, which is allocated to EESS (passive) on a primary basis.
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While there are no direct conflicts in any of these frequency bands, the 17.7-18.6 GHz and 18.8-19.3 GHz bands bracket the 18.6-18.8 GHz band, which is allocated to EESS (passive) on a primary basis and is used for a wide range of ocean- and land-related remote sensing.
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Agenda Item 1.17 is examining use of the 17.7-18.6 GHz and 18.8-19.3 GHz bands (among others) for space-to-space links.
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considered to be national assets, it is essential that the scope for such damage be assessed and steps taken to eliminate the associated risk should the allocations envisioned in this agenda item be enacted. Recommendation: The committee urges that any consideration of new or revised allocations to the 17.6-18.6 and 18.8-19.3 GHz bands explicitly consider the impact to the 18.6-18.8 GHz band, which is allocated to EESS (passive)
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VIEWS ON SELECTED WRC-23 AND WRC-27 AGENDA ITEMS 61 from cases where a non-GSO transmitter and an EESS (passive) sensor are in close proximity, with their beams aligned, and of strategies to eliminate the risk of such damage, must be com pleted before decisions are made on Agenda Item 1.17.
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"in order to consider a possible new primary allocation to the FSS (space-to-Earth) in the frequency band 17.3-17.7 GHz for Region 2, while ensuring the protection of existing primary allocations in the same and adjacent frequency bands, as appropriate." Of concern for the scientific services is the adjacent EESS (active)
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, and ground-based radar observations in the same frequency bands used during the SnowEx series of experiments. The frequency band 17.2-17.3 GHz is, therefore, a critical band for snow cover and SWE observations. Any adjacent services must be designed to protect this band for future airborne and spaceborne EESS operations for this Earth system variable.
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Earth Exploration-Satellite Service A particular concern for this agenda item is the impact of outof-band emissions and harmonics on space weather monitors for ionosphere, plasmasphere, and magnetosphere characterization, as enumerated in ITU-R RS.2456-0. The potentially affected sensors include passive systems such as L band radionavigation-satellite service (RNSS)
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Radio Astronomy Service Radio telescopes covering HF to UHF/SHF bands above the ionospheric cutoff (~20 MHz to 2+ GHz) are particularly powerful as solar radio flux monitors and interplanetary space weather monitors of highly geoeffective events such as coronal interaction regions (CIRs)
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. Earth Exploration-Satellite Service Active sensing and reflectometry measurements of Earth are made in channels that overlap with the frequencies under consideration for Agenda Item 9.1b.
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Recommendation: The committee recommends that protec tion from in-band and spurious emissions into overlapping and adjacent EESS allocations be considered when defining alloca tions for expanded amateur radio within the 1240-1300 MHz frequency band.
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While no frequency bands are specified, the current FS allocations in the international table of frequency allocations include those listed in Table 2.8. The myriad and complex implications of Agenda Item 9.1c are further illustrated by Figure 2.1, which shows that nearly all the EESS and RAS allocations are found either adjacent to or overlapping with allocations to fixed services.
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TABLE 2.8 List of Primary Fixed Service Allocations that Overlap or Are Adjacent to Science Service Allocations FIXED Allocation Science Services Radio Regulation 13.36-13.41 MHz RAS co-primary RR 5.149 25.21-25.55 MHz RAS adjacent: 25.55-25.67 MHz RR 5.149 29.7-47 MHz ras secondary: 37.5-38.25 MHz RR 5.149 68-74.8 MHz, Regions 1 and 3 RAS in footnote: 73-74.6 MHz in Regions 1 and 3 RR 5.149 72-73 MHz, Region 2 RAS adjacent: 73-74.6 MHz, Region 2 74.6-74.8 MHz, Region 2 RAS adjacent: 73-74.6 MHz, Region 2 150.05-156.4875 MHz RAS co-primary: 150.05-153 MHz, Region 1 RR 5.149 RAS co-primary: 150.05-153 MHz, Australia and India RR 5.225 174-328.6 MHz, Region 3 ras secondary: 225-235 MHz, China only RR 5.250 216-328.6 MHz, Region 2 RAS co-primary: 322-328.6 MHz, all Regions RR 5.149 230-328.6 MHz, Region 1 406.1-430 MHz RAS co-primary: 406.1-410 MHz RR 5.149 470-890 MHz RAS co-primary: 608-614 MHz, Region 2 and India RR 5.307 RAS co-primary: 606-614 MHz, in the African Broadcasting Area and RR 5.149, RR 5.304, RR 5.305 China ras secondary: 608-614 MHz in Region 1, except for African RR 5.149, RR 5.306 Broadcasting Area, and Region 3 1350-1400 MHz RAS in footnote: 1330-1400 MHz RR 5.149 eess/srs secondary: 1370-1400 MHz RR 5.339 RAS/EESS/SRS adjacent: 1400-1427 MHz RR 5.340 1427-1525 MHz RAS/EESS/SRS adjacent: 1400-1427 MHz RR 5.340 69 continued
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70 TABLE 2.8 Continued 1668.4-1690 MHz RAS co-primary: 1668.4-1670 MHz RR 5.149 RAS adjacent: 1660-1668.4 MHz RR 5.149 1700-2690 MHz ras secondary: 1718.8-1722.2 MHz RR 5.149, RR 5.385 eess/srs secondary: 2640-2690 MHz RR 5.339 ras secondary: 2655-2690 MHz RR 5.149 RAS/EESS/SRS adjacent: 2690-2700 MHz RR 5.340 3300-4200 MHz RAS in footnote: 3332.0-3339.0 MHz RR 5.149 RAS in footnote: 3345.8-3352.5 MHz RR 5.149 4400-5000 MHz ras secondary: 4800-4990 MHz RAS co-primary: 4825-4835 MHz and 4950-4990 MHz in RR 5.149, RR 5.443 Argentina, Australia, and Canada RAS in footnote: 4825-4835 MHz RR 5.149 RAS in footnote: 4950-4990 MHz RR 5.149 eess/srs secondary: 4950–4990 MHz RR 5.339 RAS co-primary 4990-5000 MHz RR 5.149 5850-8500 MHz RAS in footnote: 6650-6675.2 MHz RR 5.149, RR 5.458A EESS in footnote: 6425-7075 MHz and 7075-7250 MHz RR 5.458 10.0-10.45 GHz, Regions 1 and 3 EESS(active) co-primary: 10.0-10.4 GHz RR 5.474A, 5.474B, 5.575C 10.5-10.68 GHz RAS/EESS co-primary: 10.6-10.68 GHz RR 5.149, RR 5.482A RAS/EESS/SRS adjacent: 10.68-10.7 GHz RR 5.340, RR 5.483 10.68-10.7 GHz, RR 5.483 RAS/EESS/SRS co-primary: 10.68-10.7 GHz RR 5.340 10.7-11.7 GHz RAS/EESS/SRS adjacent: 10.68-10.7 GHz RR 5.340, RR 5.483 12.75-13.25 GHz EESS(active)
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14.4-15.35 GHz ras secondary: 14.47-14.5 GHz RR 5.149 eess secondary: 15.2-15.35 GHz RR 5.339 RAS/EESS/SRS adjacent: 15.35-15.4 GHz RR 5.340 17.7-19.7 GHz EESS(passive) co-primary: 18.6-18.8 GHz 21.2-23.6 GHz EESS(passive)
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72 TABLE 2.8 Continued 81-86 GHz RAS co-primary: 81-86 GHz RR 5.149 RAS adjacent: 79-81 GHz RR 5.149 RAS/EESS/SRS adjacent: 86-92 GHz RR 5.340 92-94 GHz RAS co-primary: 92-94 GHz RR 5.149 RAS/EESS/SRS adjacent: 86-92 GHz RR 5.340 94.1-100 GHz RAS co-primary: 94.1-100 GHz RR 5.149 RAS/EESS/SRS adjacent: 100-102 GHz RR 5.340 102-109.5 GHz RAS co-primary: 102-109.5 GHz RR 5.149 RAS/EESS/SRS adjacent: 100-102 GHz RR 5.340 RAS/EESS/SRS adjacent: 109.5-111.8 GHz RR 5.340 111.8-114.25 GHz RAS co-primary: 111.8-114.25 GHz RR 5.149 RAS/EESS/SRS adjacent: 109.5-111.8 GHz RR 5.340 RAS/EESS/SRS adjacent: 114.25-116 GHz RR 5.340 122.25-123 GHz EESS(passive) adjacent: 119.95-122.25 GHz 130-134 GHz RAS co-primary: 130-134 GHz RR 5.149, RR 5.562A EESS(active)
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adjacent: 235-238 GHz 238-241 GHz EESS(passive) adjacent: 235-238 GHz RAS adjacent: 241-248 GHz RR 5.149 252-275 GHz RAS co-primary: 252-275 GHz RR 5.149 RAS/EESS/SRS adjacent: 250-252 GHz RR 5.340 NOTE: Science Services written in all uppercase letters denote primary/co-primary allocations.
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Accordingly, in cases where emission from Fixed Services contaminates the EESS signals, the only recourse is to excise the affected observations from the data record. As undesirable as this circumstance is, it is vastly preferable to cases where contaminating emitters become mobile, and, as Agenda Item 9.1c seems to be seeking to consider, far more numerous and widespread.
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Thus, sharing studies must include not only consideration of aggre gate interference, but also the requirements for robust geoloca tion information and geolocation tracking that are necessary to enforce geographic restrictions and other effective spectrum sharing techniques. Further, in the advent of future allocations to the mobile service in these broad frequency bands, the com mittee believes that the most effective protection would be through primary allocations to the RAS for all of the relatively small bands designated in RR 5.149 that could be impacted negatively by such allocations through aggregate interference from in-band, out-of-band, and spurious emissions.
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Earth Exploration-Satellite Service The 36-37 GHz band is critical for satellite passive microwave measurements primarily of precipitation and sea ice. This band is the most widely used passive microwave channel between the 22 GHz water vapor line and the 60 GHz oxygen line complex, providing unmatched radiometric sensitivity to key Earth system variables.
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(km) AMSR2 JAXA GCOM-W1 36.5 V,H 1000 10 × 10 GMI NASA GPM 36.5 V,H 700 13 × 22 WindSat DoD Coriolis 37.0 V,H,3,4 2000 6.25 × 12.5 AMR/ NOAA JASON-2/3 34.0 V 700 25 AMR-C and JASON- CS-A/B (nominal, with H backup)
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within the frequency band 36-37 GHz (Resolution 243 (WRC-19)
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VIEWS ON SELECTED WRC-23 AND WRC-27 AGENDA ITEMS 79 criteria. Given that the GMI footprint is several hundred square kilometers, the potential for a large number of base stations in the footprint is high, with the corresponding concern that the aggregate out-of-band emissions from IMT base stations alone will exceed the maximum interference criteria.
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The frequency bands 241-250 GHz and 252-275 GHz are listed in RR 5.149, where administrations are urged to take all practicable steps to protect radio astronomy from harmful interference. The main application of EESS (passive)
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have lines spaced relatively sparingly in the submillimeter spectrum, making the regions around these lines particularly attractive for current and future planned instruments. Broadening of spectral lines by molecular collisions dictates that bandwidths of order 1 GHz must be used to capture the full line shape and deduce the atmospheric composition profiles.
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Radio Astronomy Service The frequency range between 231.5-700 GHz is heavily used for radio astronomy observations of numerous molecular line transitions, which has resulted in major advances in the nascent field of astrochemistry. Because of high atmospheric absorption due to water vapor, ground-based observations at these frequencies can only be made from high and arid sites, in spectral windows bounded by strong water lines.
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Arizona Radio 720 Arizona, 32.7 −109.9 3,160 Observatory USA Submillimeter Telescope (ARO SMT) Atacama Large 950 Chile −23.0 −67.8 5,075 Millimeter/ submillimeter Array (ALMA)
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This frequency range is also essential for continuum observations of emission from dust throughout the universe. This spectral region is also important for the study of life in the universe.
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. When spectral protection is not feasible, dynamic frequency allocation and geofencing should be used to protect the science services.
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National Academies of Sciences, Engineering, and Medicine on Agenda Items of Interest to the Science Services at the World Radiocommunication Conference 2019, Washington, DC: The National Academies Press, https://doi.org/10.17226/24899, pp.
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Satellite Missions Relevant to WRC-27 Agenda Items 2.2 and 2.3a,b Relevant Center Frequency Bandwidth Sensor Satellite (GHz)
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National Academies of Sciences, Engineering, and Medicine on Agenda Items of Interest to the Science Services at the World Radiocommunication Conference 2019, Washington, DC: The National Academies Press, https://doi.org/10.17226/24899, p.
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Radio Astronomy Service Of particular concern for radio astronomy are the frequency bands at 42.5-43.5 GHz and 48.94-49.04 GHz, which are at risk from adjacent and in-band transmissions, respectively. As noted in RR 5.149, radio astronomy is particularly vulnerable to spaceborne radio interference because terrain shielding cannot be utilized to block transmissions originating at high altitude.
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Because the sensitivity of continuum observations increases with the bandwidth of the observation, and because this band is the only RAS band below 75 GHz that is a full gigahertz wide, the band is extremely valuable scientifically. Continuum observations in this band provide critical information on the physical state of the interstellar medium associated with starforming regions, and observations at this frequency have been used to measure the cosmic microwave background emission that reveals details of the early universe.
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sensors at these frequency bands. The introduction of aeronau tical and maritime Earth stations in motion (ESIMs)
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. As all of these agenda items involve the same 71-76 GHz and 81-86 GHz frequency regions, they are considered jointly herein.
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Satellite Missions Relevant to WRC-27 Agenda Items 2.4, 2.5, and 2.7 Center Frequency Bandwidth Sensor Satellite (GHz)
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; Mopra and the Australia Telescope Compact Array (ATCA) in Australia; the Nobeyama 45 m Telescope in Japan; the Effelsberg 100 m Radio Telescope in Germany; the IRAM 30 m in Spain; the 12 m Greenland telescope currently sited at Thule; the Atacama Large Millimeter Array (ALMA)
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Recommendation: The committee urges that a comprehensive study of in-band, out-of-band, and spurious emissions be an integral part of work on these future agenda items. The com mittee notes that radio astronomy observatories that operate at these high frequencies are usually located at high, dry sites so that little, if any, terrain shielding is in effect and there is little protection from atmospheric attenuation.
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96 WORLD RADIOCOMMUNICATION CONFERENCE 2023 WRC-27 AGENDA ITEM 2.6: SPACE WEATHER Proposed WRC-27 Agenda Item 2.6 is "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 Radiocommunication Sector studies reported to WRC-23 under Agenda Item 9.1 and its corresponding Resolution 657 (Rev.WRC-19) ." The applicable topic from Agenda Item 9.1 is discussed above.
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for transmissions in the space-to-Earth direction from MSS space stations operating at higher orbital altitudes, including GSO, towards non-GSO MSS satellites, may increase spectral efficiency in these frequency bands." Resolution 249 (WRC-19) also recognizes "that it is necessary to study the impact on other services . . .
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recognizes "that out-of-band emissions, signals due to antenna pattern sidelobes, reflections from receiving space stations and in-band unintentional radiation due to Doppler shifts may impact services operating in the same and adjacent or nearby frequency bands." In this con text, it is important to note that RAS has co-primary allocations at 1610.6-1613.8 MHz and 1660-1670 MHz and that RR 5.402 notes that "the use of the band 2483.5-2500 MHz by the mobile-satellite and the radiodetermination-satellite services is subject to coordination under No 9.11A. Administrations are urged to take all practicable steps to prevent harmful interference to the radio astronomy service from emissions in the 2483.5-2500 MHz band, especially those caused by second-harmonic radiation that would fall into the 4990-5000 MHz band allocated to the radio astronomy service worldwide." Resolution 250 (WRC-19)
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From page 99... ...
In particular, the proposed spaceto-space transmissions in the space-to-Earth direction will illuminate locations on Earth that are not targeted specifically and thus run the risk of direct illumination of radio astronomy receivers unless the geographic region illuminated is also considered. Of the frequency bands under consideration currently for WRC-27 Agenda Item 2.8, RAS is co-primary at 1610.6-1613.8 MHz
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From page 100... ...
L band and S band are workhorse frequency ranges for radio astronomy observations of faint cosmic sources. Within these frequency bands are significant spectral lines, including the spin-flip of neutral hydrogen with a rest frequency of 1420.4058 MHz and several different rotational transitions associated with the hydroxyl radical (OH)
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From page 101... ...
However, due to the expansion of the universe, spectral lines for more distant objects are redshifted relative to their rest-frame transition frequen cies and thus require access to lower frequency bands to detect these spectral lines in sources outside of the Milky Way Galaxy. The large frequency band identified for redshifted neutral hydrogen observa tions enables measurement of the gas content of galaxies within a volume with a radius of approximately 1 billion light years.
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From page 102... ...
. Although none of the proposed frequency bands under consideration for WRC-27 Agenda Item 2.8 and Agenda Item 2.9 are adjacent to this passive band, it is important to note that contamination in these channels 9 While the former 305-m telescope at Arecibo Observatory is no longer functional, a 12-m radio telescope is operational at the site and the observatory remains open.
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From page 103... ...
RFI contamination of the SMAP and SMOS sensors, for example, has resulted in reduced quality and capability to monitor the variables that are used in weather and climate applications as well as natural hazards monitoring. The data stream from these satellites are the most reliable current source of surface soil moisture information that is used in Earth system science as well as impactful drought monitoring and flood forecasting natural hazards mitigation and must be protected from out-of-band and spurious emissions.
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Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.