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 (2017) / Chapter Skim
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2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items
2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items
Pages 12-56
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in 2019 and preliminary agenda items for WRC-23.
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Globally, facilities include the Giant Metrewave Radio Telescope in India, the Parkes 64-m in Australia, the Dominion Radio Astrophysical Observatory Synthesis Telescope in Canada, the Radio Telescope Effelsberg in Germany, the Nancay RadioHeliograph in France, and future facilities such as the Square Kilometer Array (SKA) Molongolo Prototype (SKAMP)
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Near 400 MHz, satellite and ground-based phasecoherent radio beacons measure total electron content (TEC) and the amplitude and phase fluctuations in the trans-ionospheric signals (i.e., scintillations)
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This spectral line is highly sensitive to small changes in atmospheric water vapor concentrations, and it is pressure broadened, with some contributions from spectral continuum, which must be measured in the adjacent Ku and Ka bands. These continuum observations are at risk with the proposed frequency allocations to ESIM.
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It has a strong influence on Earth's atmospheric radiation budget and, consequently, influencing climate, formation of clouds, and recipitation -- making its precise measurement vital.3 Lack of p water vapor measurements will have a detrimental impact on accurate weather forecasting, including hurricane tracking and landfall prediction, and precise projection for extreme weather events such as hail storms, thunderstorms, tornadoes, and sheer winds.4 Without such measurements, scientists would not be able to monitor and forecast El Niño Southern Oscillations, affecting prediction of expected storms during hurricane season and of drought, forest fires, flooding, and landslides. Water vapor measurements are indispensable for agricultural and food security, disease dissemination, 3 R
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Further degradation of this band will severely limit the validity of these water vapor measurements. Radio Astronomy Service While there are no allocations to RAS within these frequency ranges, many radio telescopes, such as the VLA and the GBT in the United States, have receivers that operate at these frequencies.
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from the adjacent frequency allocations to nonGSO FSS systems. As noted in Footnote US342, radio astronomy is particularly vulnerable to space-borne radio interference because terrain shielding cannot be utilized to block transmissions originating at high altitude.
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The detrimental levels for continuum and spectral line radio astronomy observations are −227 dBW/m2/Hz and −210 dBW/m2/Hz for the average across the full 1 GHz band and the peak level in any single 500 kHz channel (ITU-R RA.769, Tables 1 and 2, respectively)
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While the 36-37 GHz band is co-primary with Fixed and Mobile services as well as Space Research passive services, effective EESS compatibility has been due to limited use of this band by other services. That said, increased use in the 37.5-39.5 GHz band must allow for a sufficient guard band to protect these and follow-on EESS instruments from widespread transmission from services in adjacent bands.
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bands at 36-37 GHz and 50.2-50.4 GHz is critical for global weather forecasting and climate research. Emission limits, as specified in radio regulations 5.555B and ITU-R RA.769-2, should be respected, and guard bands should be implemented to protect frequency allocations to passive scientific services from out-of-band emissions.
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Of key import for this agenda item is that propagation is largely unimpeded by the atmosphere at these low frequencies so that geographic shielding is largely ineffective. Radio Astronomy Service There are primary allocations from 150.05-153 MHz and 406.1-410 MHz to RAS within the bands being considered.
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Earth Exploration-Satellite Service Techniques for remote sensing of the ionosphere include study of ionospheric coupling to the lower atmosphere below and the larger heliospheric environment above, using both passive and active techniques over a wide range of frequency bands. Near 150 MHz, satellite and ground-based phase coherent radio beacons measure TEC and the amplitude and phase fluctuations in the trans-ionospheric signals (i.e., scintillations)
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This is particularly impor tant since, in many cases, at these frequencies, satellite trans missions will be made directly into the main beam of the indi vidual elements of the radio telescope array. Further, if new allocations are made, Radio Regulations 5.208A and 5.208B and Resolution 739 should be updated to reflect the impor tance of protecting radio astronomy services in these bands.
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Radio Astronomy Service The 1610.6-1613.8 MHz band is used for spectral line observations of the hydroxyl radical (OH)
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. Recommendation: The committee supports modernization of the Global Maritime Distress Safety Systems as long as radio astronomy operations are protected.
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Radio Astronomy Service There is a primary allocation to RAS from 150.05-153.0 MHz. There are several existing and planned radio astronomy facilities that operate in the 150-153 MHz frequency range.
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Up to 10 MHz bandwidth is planned for future systems. The Irkutsk incoherent scatter radar currently operates at these frequencies.8 Recommendation: Any spectrum allocation should be done in such a way so as to preserve access of the Radio stronomy A Service and the Earth Exploration-Satellite Service to the bands allocated to them, including appropriate frequency separations that conform to ITU-R RA.769 and ITU-R RS.2017.
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There are several existing and planned facilities operating in the 150-153 MHz frequency range that conduct observations of the Sun, the interstellar medium, pulsars, steep spectrum sources, and active galaxies, as well as the EoR, when the first luminous sources emerged in the universe. Facilities in the United States include HERA, which is being tested at Green Bank and Berkeley and will be built in South Africa.
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This is particularly important since in many cases, at these frequencies, satellite transmis sions will be made directly into the main beam of the indi vidual elements of the radio telescope array. Further, if new allocations are made, RR 5.208A and 5.208B and Resolution 739 should be updated to reflect the importance of protecting radio astronomy services in these bands.
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For simplicity in the headers, the broad frequency ranges are referred to as "24 GHz Band": 24.25-27.5 GHz; "31 GHz Band": 31.8-33.4 GHz; "37/42 GHz Bands": 37.0-40.5 GHz, 40.5-42.5 GHz, and 42.5-43.5 GHz; "47/50 GHz Bands": 45.5-47 GHz, 47-47.2 GHz, 47.2-50.2 GHz, and 50.4-52.6 GHz; and "70/80 GHz Bands": 66-76 GHz and 81-86 GHz. 10 FCC Docket RM-11713.
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in Korea; DASI at the South Pole; the Delingha Observation Station and the planned Qitai Radio elescope in China; the RATAN-600, Galenki RT-70, and T Suffa RT-70 radio telescopes in Russia; and the Yevpatoria RT-70 radio telescope in Crimea. In addition, radio astronomy observatories are particularly vulnerable to out-of-band emission (OOBE)
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Measurements of these masers yield important information on stellar temperature, density, wind velocities, and other parameters. The 42.5-43.5 GHz band is also one of the preferred RAS bands for continuum observations.14 The detrimental levels for continuum and spectral line radio astronomy observations are −227 dBW/m2/Hz and −210 dBW/m2/Hz for the average across the full 1 GHz band and the peak level in any single 500 kHz channel (ITU-R RA.769, Tables 1 and 2, respectively)
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70/80 GHz Bands The IMT allocations at 66-76 GHz and 81-86 GHz are located near protected frequency bands for RAS. Radio astronomy observatories are to be protected from harmful interference in the frequency range 76-86 GHz (ITU RR 5.149)
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. 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.
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and is 250 MHz from the lower edge of the frequencies under consideration. The protected band is intended to cover a water vapor absorption line that is unique in the atmosphere in that it is not opaque at sea level.
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Data products obtained from this frequency band include cloud liquid water and integrated water vapor, both of which are key to initializing global weather forecast models. There is significant concern regarding OOBE from the proposed adjacent IMT band at 31.8-33.4 GHz because the instrument filter rejection levels for typical EESS sensors are limited.
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Of particular concern is that the proposed IMT bands will offer no protection for these EESS instruments because the band definitions line up precisely with the allocated passive bands. Further ore, with lower orbits and larger receiver antennas, m these EESS passive sensors are far more susceptible to terrestrial interference than the ATMS described above.
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70/80 GHz Bands The IMT allocation at 81-86 GHz is immediately adjacent to a protected EESS (passive) band at 86-92 GHz, for which all emissions are prohibited (RR 5.340)
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, respectively. In addition to an exclusion zone around each RAS facility, likely growth of the International Mobile Telecommunications service and the impact of future aggregate interference must be taken into account.
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from harmful interference. Radio Astronomy Service Of significant concern for RAS is that radio astronomy is particularly vulnerable to high-altitude emissions (such as airborne or space-borne transmitters)
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. This frequency range is used by radio astronomers for the detection of complex molecules and for continuum observations of radio sources (see also Agenda Item 1.13)
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. This protected band is intended to cover a water vapor absorption line (see also Agenda Item 1.13)
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As many of the scientific concerns remain the same, the discussion below includes text from the Views of the National Academies on the World Radiocommunication Conference 2012.20 Radio Astronomy Service Protection of the atmospheric windows for passive use in the 275-450 GHz frequency range is highly desirable because the sub millimeter range of the radio spectrum is a prime region for molecular spectroscopy and for studying continuum emission from dust (see Table 2.4) .21 In particular, with the increased sensitivity afforded by ALMA, the exploration of the universe using this part of the 20 National Research Council, Views of the National Academy of Sciences and the N ational Academy of Engineering on Agenda Items at Issue at the World Radiocommunication Conference 2012, The National Academies Press, Washington, D.C., 2013.
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TABLE 2.4 Selected Spectral Lines between 275 and 450 GHza Spectral Line Transition Frequency (GHz) Significance CO 3-2 345 Important tracer of galactic and extragalactic structure 4-3 461 Probe of star-forming regions and protoplanetary disks HCO+ 4-3 356 Probe of high-density regions, protostellar cores 5-4 446 HCN 4-3 354 Probe of high-density regions, protostellar cores, 5-4 443 Inner shells of evolved stars CS 6-5 293 Dense protostellar cores, evolved stars, planetary nebulae 7-6 342 8-7 392 9-8 440 H 3O + 1(1)
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. However, by necessity, radio astronomy facilities observing at these high frequencies are located at sites with typi cally low atmospheric attenuation (i.e., dry sites at high altitudes)
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to 414 GHz.23 For context, this oxygen line was 22 National Research Council, Views of the National Academy of Sciences and National Academy of Engineering on Agenda Items at Issue at the World Radiocommunication Conference 2012, The National Academies Press, Washington, D.C., 2013.
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Information about the dust emission in these protoplanetary disks comes from submillimeter continuum observations. For example, 350 GHz continuum observations of TW Hydrae traced millimeter-sized particles on spatial scales as small as 1 astronomical unit.25 The series of concentric ring-shaped substructures in this system suggests interactions between the disk and young planets.
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Unlike RAS measurements, where geographic exclusion zones may be sufficient, EESS measurements are global and require protection in all ITU-R Regions. Significant applications in this band include determination of columnar water vapor, temperature, and molecular species that play critical roles in atmospheric science, ozone, and carbon cycle monitoring.
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Water vapor sounding TWICE, GEM, GOMAS 397-399 2000 Water vapor sounding GOMAS 409-411 2000 Temperature sounding
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a Adapted from Table 2 in ITU-R RS.515-5. SOURCE: National Research Council, Views of the National Academy of Sciences and National Academy of Engineering on Agenda Items at Issue at the World Radiocommunication Conference 2012, The National Academies Press, Washington, D.C., 2013, Table 1.6-3.
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26 National Research Council, Views of the National Academy of Sciences and National Academy of Engineering on Agenda Items at Issue at the World Radiocommunication Conference 2012, The National Academies Press, Washington, D.C., 2013. 27 Nuclear Threat Initiative, Counterproliferation of Weapons of Mass Destruc tion, Chapter XII in Joint Warfighting Science and Technology Plan, http://www.nti.
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From page 53... ...
and WAS/RLAN is not feasible. Resolution 239 recommends studies to facilitate sharing with incumbent systems in the frequency bands 5150-5350 MHz, 5350-5470 MHz, 5725-5850 MHz, and 5850-5925 MHz, with a specific mention to determine whether any additional mitigation techniques in the frequency band 5350-5470 MHz beyond those analyzed previously could provide coexistence between WAS/RLAN systems and EESS (active)
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in the 5350-5470 MHz band from unwanted emissions from planned radio local area networks (WAS/RLAN) units.
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." Radio Astronomy Service It is important that the studies consider the impact of the orbiting radar on existing radio telescopes operating at similar frequencies or near the harmonics. These facilities include the Long Wavelength Array stations in New Mexico and California, LOFAR in the Netherlands (with international stations across Europe)
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56 WORLD RADIOCOMMUNICATION CONFERENCE 2019 remote sensing observations should be explored. The commit tee endorses the importance of the pending characterization of the new radar system in time for WRC-23.
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