National Academies Press: OpenBook

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: 2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items

« Previous: 1 Introduction
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

2

Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items

The following pages provide a discussion of the committee’s consensus opinions on the potential impact and relevance of certain agenda items at issue at the upcoming World Radiocommunication Conference (WRC) in 2019 and preliminary agenda items for WRC-23.

Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

AGENDA ITEM 1.2:
POWER LIMITS FOR EARTH STATIONS

Agenda Item 1.2 considers “in-band power limits for Earth stations operating in the mobile-satellite service, meteorological-satellite service and Earth exploration-satellite service in the frequency bands 401-403 MHz and 399.9-400.05 MHz, in accordance with Resolution 765 (WRC-15).”

This agenda item invites the consideration of in-band power limits for Earth stations for the Earth Exploration-Satellite Service (EESS) (Earth-to-space) and meteorological-satellite service (MetSat) (Earth-to-space) services.

Radio Astronomy Service

There is a nearby primary allocation from 406.1-410 MHz to the Radio Astronomy Service (RAS). Care should be taken that out-of-band emission (OOBE) levels conform to the listed detrimental power levels in RA.769, even with the establishment of maximum allowed power levels in this neighboring frequency range. The committee notes that several major RAS facilities in the United States operate in or near this frequency range, including the Robert C. Byrd Green Bank Telescope (GBT), the Karl G. Jansky Very Large Array (VLA), the Very Long Baseline Array (an instrument with 10 discrete receiving stations spread over North America), the Owens Valley Radio Observatory, the Sagamore Hill Solar Observatory, and the Arecibo Observatory. 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) in Australia and the Five-hundred-meter Aperture Spherical Radio Telescope (FAST) in China. Of particular scientific interest in this band are studies of the Sun, the interstellar medium, pulsars, steep spectrum sources, and active galaxies.

Earth Exploration-Satellite Service

Radio frequencies below 1 GHz are used to understand the physical state of the ionosphere, characterize irregularities, detect large-scale structures, and enable the real-time monitoring and prediction of propagation conditions and space weather effects.

Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

Such understanding enables important scientific and commercial applications, including communications, precision navigation, and environmental remote sensing. 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 400 MHz, satellite and ground-based phase-coherent radio beacons measure total electron content (TEC) and the amplitude and phase fluctuations in the trans-ionospheric signals (i.e., scintillations) related to the irregularities along the propagation path. One beacon currently on-orbit operates at 400.032 MHz; and an on-ground beacon operates at 401.25 MHz. Both active transmissions from such satellite beacons and passive observations of radio source scintillation (RSS), related to ionospheric structure, are routinely conducted at these frequencies.1

Conclusion: The committee concurs with the placement of carefully considered power limits for Earth stations operating in these bands.

___________________

1 Portions of this text are taken from National Academies of Sciences, Engineering, and Medicine, Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses: Second Edition, The National Academies Press, Washington, D.C., 2015.

Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

AGENDA ITEM 1.5:
EARTH STATIONS IN MOTION

Agenda Item 1.5 considers “the use of the frequency bands 17.7-19.7 GHz (space-to-Earth) and 27.5-29.5 GHz (Earth-to-space) by Earth stations in motion communicating with geostationary space stations in the fixed-satellite service and [to] take appropriate action, in accordance with Resolution 158 (WRC-15).”

Of primary concern to the scientific services is the 18.6-18.8 GHz band that has a co-primary allocation for EESS (passive) along with Fixed, FSS (s-E) and Mobile, except for aeronautical mobile services, and Space Research (passive). The Space Research allocation is secondary in Regions 2 and 3. The emission limits and other transmission specifications in the band are regulated by radio regulations (RR) 5.522A and 5.522C. In the United States, power flux density limits in this frequency range are specified in Footnotes US254, US255, and US334.

Earth Exploration-Satellite Service

Frequency bands within the 17.7-19.7 GHz range are used extensively in many operational environments for EESS (see Table 2.1) to provide critical measurements for weather forecasting and studies of climate and environmental impacts. These measurements enable studies of clouds, precipitation, the freeze-thaw transition, snow, and ice. In addition, these measurements enable water vapor profiling and include measurements of sea surface temperatures, winds, and topography. There is significant concern that EESS observations may be contaminated by in-band and out-of-band interference from backscattered space-Earth transmissions if this frequency range is allocated to ESIM.

Specifically, a very important atmospheric water vapor absorption line is located at 22.235 GHz, where K band2 is centered. 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. Measurements of continuum emission at frequencies both below and

___________________

2 Nominal frequency ranges for Ku, K, and Ka bands are 12-18, 18-27, and 27-40 GHz, respectively.

Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

TABLE 2.1 Passive EESS Sensors in the 17.7-19.7 GHz Band Under Consideration

Sensor Satellite Center Frequency (GHz) Bandwidth (MHz)
AMSR2 GCOM-W1 18.7 200
GMI GPM 18.7 200
PMR WindSat 18.7 750
AMR-2 Jason-2 & 3 18.7 200
MWI MetOp-SG 18.7 200
MADRAS Megha-Tropiques 18.7 200
MTVZA-GY Meteor-M 18.7 200
MWRI FY-3 18.7 200
MWRI’ HY-2A 18.7 250
SSM/I DMSP-F15 19.35 250
SSMIS DMSP-F16, -F17, -F18, -F19 19.35 357

NOTE: Acronyms are defined in Appendix B.

above are critical to understand the shape of this line and to therefore derive a more precise indication of the water vapor concentration. This water vapor measurement is vital for many applications. It has a strong influence on Earth’s atmospheric radiation budget and, consequently, influencing climate, formation of clouds, and precipitation—making its precise measurement vital.3 Lack of 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. Müller, A. Kunz, D.F. Hurst, C. Rolf, M. Krämer, and M. Riese, The need for accurate long-term measurements of water vapor in the upper troposphere and lower stratosphere with global coverage, Earth’s Future 4:25-32, doi:10.1002/2015EF000321, 2016.

4 R.M. Rabin, S.F. Corfidi, J.C. Brunner, and C.E. Hane, Detecting winds aloft from water vapour satellite imagery in the vicinity of storms, Weather 59:251-257, doi:10.1256/wea.182.03, 2004.

Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

and the economy, among others. Water vapor measurements are also used to correct the path delay caused by water vapor molecules to calibrate altimeter data used for ocean geoid estimation, sea surface topography, and other remote sensing Earth variables.

Despite existing protections in the radio regulations, WindSat, the Advanced Microwave Scanning Radiometer 2, and the Global Precipitation Measurement Microwave Imager have reported radio frequence interference (RFI) over the continental United States at K band (18.7) GHz. In addition, RFI that is reflected from the ocean surface also impedes measurement of ocean surface wind speed. As an example of the increased RFI detected at 18.7 GHz, McKague et al. (2010)5 reported RFI measurements derived using the difference between observations at 23.8 and 18.7 GHz from WindSat. The data indicate an increase in RFI from 2005 to 2008 and a seasonal dependence. The data also indicate that signals from satellite downlinks, reflected from Earth’s surface, are contributing to the RFI detected in the EESS passive sensors. 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. The 17.7-19.7 GHz band is used for measurements of rare chemical species that trace the origins of stars, planets, and life (e.g., cyclopropenylidene). The 27.5-29.5 GHz band is used for broadband continuum observations of distant galaxies and quasars and studies of red-shifted lines of species such as carbon monoxide from distant galaxies and the early universe.

Recommendation: Any new Earth Stations in Motion uses should strictly preserve the extensive existing scientific use of the 18.6-18.8 GHz band. New uses of these bands should take due account of considering g) of Resolution 158 (WRC-15).

___________________

5 D. McKague, J. Puckett, and C. Ruf, Characterization of K-band radio frequency interference from AMSR-E, WindSat and SSM/I, pp. 2492-2494 in 2010 IEEE International Geoscience Remote Sensing Symposium, July 25, 2010, http://ieeexplore.ieee.org/xpl/mostRecentIssue.jsp?punumber=5639672.

Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

AGENDA ITEM 1.6:
NON-GSO FSS SATELLITE SYSTEMS AT 37-50 GHZ

Agenda Item 1.6 considers “the development of a regulatory framework for non-GSO FSS satellite systems that may operate in the frequency bands 37.5-39.5 GHz (space-to-Earth), 39.5-42.5 GHz (space-to-Earth), 47.2-50.2 GHz (Earth-to-space) and 50.4-51.4 GHz (Earth-to-space), in accordance with Resolution 159 (WRC-15).”

This agenda item calls for studies of technical, operational, and regulatory provisions for operations in the above bands, including protection of EESS (passive) in the bands 36-37 GHz and 50.2-50.4 GHz and protection of the radio astronomy service in the bands 42.5-43.5 GHz, 48.94-49.04 GHz, and 51.4-54.25 GHz.

Radio Astronomy Service

Of significant concern for RAS is the potential for out-of-band emission (OOBE) from the adjacent frequency allocations to non-GSO 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. Internationally, the following telescopes have receivers that operate in these frequency bands: Very Large Array (U.S.), Very Long Baseline Array (U.S.), Green Bank Telescope (U.S.), Haystack Radio Telescope (U.S.), Australia Telescope Compact Array (Australia), Mopra Radio Telescope (Australia), Parkes Radio Telescope (Australia), and Radio Telescope Effelsberg (Germany).

Administrations are urged to take all practicable steps to protect the radio astronomy band at 42.5-43.5 GHz from harmful interference (RR 5.149) and further regulations regarding acceptable power levels are designated in RR 5.551I and RR 5.551H. This band is used for observations of silicon monoxide (SiO) masers that have rest-frame emission lines at 42.519, 42.821, 43.122, and 43.424 GHz. Measurement of SiO masers from stars and star-forming regions in our Milky Way galaxy yield important information on stellar temperature, density, wind velocities, and other parameters. Polarization observations are also used to trace the magnetic field distribution around the stars. The 42.5-43.5 GHz band is also one of the preferred RAS bands for continuum observations. Its location in the spectrum at approximately twice the frequency of the 23.6-24 GHz continuum band, and its 1 GHz bandwidth, makes it an effective point for sampling the continuum emission at octave or better frequency intervals. Because the sensitivity of continuum observations increases

Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

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 star-forming regions, and observations at this frequency have been used to measure the cosmic microwave background emission that reveals details of the early universe. 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).

The narrow RAS frequency allocation at 48.94-49.04 GHz is used to observe carbon monosulfide (CS) in our galaxy. CS observations probe the dense interstellar medium that is the site of star-forming regions, including the formation of solar systems like our own. In addition, based on the observed isotope ratios of C32S, C33S, and C34S, radio astronomers are investigating theories of nucleosynthesis and the star formation history of the Milky Way galaxy. In this band, administrations are urged to take all practicable steps to protect the RAS from harmful interference (RR 5.149), and all airborne emissions are prohibited (RR 5.340). Furthermore, additional protections are stated in RR 5.555B: “the power flux density in the band 48.94-49.04 GHz produced by any geostationary space station in the FSS (space-to-Earth) operating in the bands 48.2-48.54 GHz and 49.44-50.2 GHz shall not exceed −151.8 dB(W/m2) in any 500 kHz band at the site of any radio astronomy station.” However, given the geographic shielding of many of the radio astronomy stations, the proposed use of 47.2-50.2 GHz for Earth-to-space transmission by non-GSO satellites is not in conflict automatically. Shared use of this frequency range must consider the existing regulations and potential impact on radio astronomy applications.

Also of concern, as noted in WRC-15 Resolution 159, is the frequency range 51.4-54.25 GHz, which is used by RAS in some nations (RR 5.556).

Earth Exploration-Satellite Service

Of critical importance for EESS is the protection of OOBE of the passive microwave observations in the 36-37 GHz band, with a co-primary allocation. This band is important for observations of weather and climate. In particular, measurements in this band are used to maintain long, time-series records of atmospheric water vapor, clouds, ocean winds, sea ice extent/concentration/type,

Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

snow depth, melt/freeze of seasonal snow, and glacier surfaces. In addition, in conjunction with observations at other bands, these measurements provide critical values for regular operations such as weather forecasts. Secondary applications include sea surface temperature and topography. Sensors operating at 37-50 GHz are listed in Table 2.2.

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.

There is also a primary allocation for EESS (passive) at 50.2-50.4 GHz, with additional protection (transmissions prohibited) under RR 5.340. Observations in this band are used to retrieve atmospheric temperature profiles. It should be noted that the combined proposed services at 47.2-50.2 GHz and at 50.4-51.1 GHz would completely surround the EESS (passive) allocation.

Of special concern is the potential for uplinks to non-GSO satellites operating near 50 GHz to interfere with downward-looking passive EESS. A simple static calculation using the ITU-R Resolution. 750-prescribed levels for FSS Earth stations in adjacent bands shows that a main-beam-to-main-beam coupling between the FSS Earth station uplink into the EESS (passive) receiver will exceed the ITU-R RS.2017 protection levels by at least 71 dB.

TABLE 2.2 EESS Sensors Operating at 37-50 GHz

Sensor Center Frequency (GHz) Bandwidth (MHz)
Windsat 37 2000
SSM/I 37 1000
SSMIS 37, 50.3 1500, 400
GMI 36.5 1000
AMSR2 36.5 1000
AMSUA 50.3 180
ATMS 50.3, 51.76 180, 400

NOTE: In addition to providing critical scientific observations, building and deploying these sensors represents a multibillion dollar U.S. investment. Acronyms are defined in Appendix B.

Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

Recommendation: Given the scientific importance of the 42.5-43.5 GHz and 48.94-49.04 GHz Radio Astronomy Service (RAS) frequency allocations, any Fixed-Satellite Service allocations to non-geostationary orbit satellite systems should consider the impact of aggregate emissions, both out-of-band and in-band, on the neighboring and coexisting RAS allocations. Similarly, continued protection of the Earth Exploration-Satellite Service (EESS) (passive) 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. A static analysis should be included to make sure that Earth stations near the equator radiating toward zenith do not exceed the protection levels stipulated by Recommendation ITU-R RS.2017 into the downward-looking EESS (passive) receivers. This is particularly important given that the EESS sensors operating at 50.2-50.4 GHz are nadir-pointing.

Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

AGENDA ITEM 1.7:
SPECTRUM NEEDS FOR NON-GSO SATELLITES

Agenda Item 1.7 considers “spectrum needs for telemetry, tracking and command in the space operation service for non-GSO satellites with short duration missions, to assess the suitability of existing allocations to the space operation service, and, if necessary, to consider new allocations, in accordance with Resolution 659 (WRC-15).”

The frequency ranges under consideration are 150-174 MHz and 400.15-420 MHz. 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. ITU RR 5.149 urges administrators to take all practicable steps to protect the RAS from harmful interference in the 150.05-153 MHz frequency range (Region 1) and the 406.1-410 MHz frequency range (global). The detrimental interference levels for these bands are −259 dBW/m2/Hz and −255 dBW/m2/Hz, respectively (ITU-R RA.769, Table 1). A proposed allocation within this range could have a severe impact on RAS, making it difficult or impossible to conduct scientific research in these bands. In particular, radio telescopes can be greatly impacted by space-to-Earth transmissions because emissions from satellites often come from high-elevation angles directly into the main beam of radio telescopes. Significantly, at these low frequencies, radio telescopes have a correspondingly larger primary beam. The typical antennas used at these frequencies have significant receptivity in all directions, and strong interference places difficult demands on the dynamic range of the signal processing systems. In these circumstances, the presence of strong interference anywhere in the sky may corrupt the observations or require excessive computational resources to mitigate the interference in post-processing analysis. Thus, at these frequencies, RAS observations are particularly vulnerable to interference from satellite operations.

The committee notes that several major RAS facilities operate in the 406-410 MHz frequency range, including the GBT, the VLA, the Very Long Baseline Array (an instrument with 10 discrete receiving stations spread over North America), the Owens Valley Radio Observatory, the Sagamore Hill Solar Observatory, and the Arecibo Observatory, all in the United States. Globally, facilities

Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

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 SKAMP in Australia and FAST in China. Of particular scientific interest in this band are studies of the Sun, interstellar medium, pulsars, steep spectrum sources, and active galaxies.

There are several existing and planned facilities operating in the 150-153 MHz frequency range that conduct observations for the above scientific topics and also for studies of the epoch of reionization (EoR), when the first luminous sources emerged in the universe. Existing facilities in the United States include the Hydrogen EoR Array (HERA), which is being tested at Green Bank and the University of California, Berkeley, and will be built in South Africa. International facilities working in this frequency range include the Low Frequency Array (LOFAR) in the Netherlands (and stations across Europe), the Murchison Widefield Array (MWA) in Australia, the Mauritius Radio Telescope, and the Giant Metrewave Radio Telescope in India. Future facilities that will eventually operate in this frequency range include FAST in China and the low-frequency component of the Square Kilometer Array (SKA-Low), being planned for Australia.

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) related to the irregularities along the propagation path. One beacon currently on-orbit operates at 150.012 MHz. Both active transmissions from satellites and observation of RSS are routinely conducted. A relatively new field of ionospheric and plasmaspheric remote sensing has recently opened using ground-based interferometers operating at meter wavelengths. For example, the P-band system on the VLA (~236-492 MHz) measures tiny fluctuations in TEC (or delta-TEC). These fluctuations can be caused by a variety of disturbances, including natural (e.g., from space weather) and human-made (e.g., from underground explosions). Measurements are made by utilizing natural cosmic sources as background beacons against which ionized atmospheric turbulence and waves

Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

can be characterized and tracked. Ionospheric remote sensing measurements are also conducted from the MWA in Australia (80-300 MHz) and LOFAR in Europe (10-90 MHz, 110-250 MHz).6

Recommendation: Any spectrum allocation should be done in such a way so as to preserve access of the Radio Astronomy Service and Earth Exploration-Satellite Service to the bands allocated to them, including appropriate frequency separations conforming to the interference criteria provided in ITU-R RA.769 and ITU-R RS.2017. This is particularly important since, in many cases, at these frequencies, satellite transmissions will be made directly into the main beam of the individual 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 importance of protecting radio astronomy services in these bands.

___________________

6 Portions of this text are taken from National Academies of Sciences, Engineering, and Medicine, Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses: Second Edition, The National Academies Press, Washington, D.C., 2015.

Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

AGENDA ITEM 1.8:
GLOBAL MARITIME DISTRESS SAFETY SYSTEMS

Agenda Item 1.8 considers “possible regulatory actions to support Global Maritime Distress Safety Systems (GMDSS) modernization and to support the introduction of additional satellite systems into the GMDSS, in accordance with Resolution 359 (Rev. WRC-15).”

This agenda item proposes to use the Mobile Satellite (Earth-to-space) and Aeronautical Radio Navigation bands between 1616-1626.5 MHz, or parts thereof, to add an additional satellite system into the GMDSS. Resolution 359 specifically calls for protection for allocations in neighboring bands, which include a radio astronomy band at 1610.6-1613.8 MHz.

Radio Astronomy Service

The 1610.6-1613.8 MHz band is used for spectral line observations of the hydroxyl radical (OH). The OH transition at rest frequency 1612 MHz is one of the most important spectral lines for RAS and is listed as such in Recommendation ITU-R RA.314. OH was the first cosmic radical to be detected at radio frequencies and continues to be a powerful research tool. In its ground state, the OH molecule produces four spectral lines at frequencies of approximately 1612, 1665, 1667, and 1720 MHz, all of which have been observed in emission and in absorption in our Milky Way galaxy, as well as in external galaxies. The study of OH lines provides information on a wide range of astronomical phenomena—for example, the formation of protostars and the evolution of stars. To interpret most observations made of the OH molecule, it is necessary to measure the relative strength of several of these lines. The loss of the ability to observe any one of these lines will prevent the study of these classes of physical phenomena.

Spectral line observations are made using spectrometers that can simultaneously integrate the power in each of a large number of frequency channels distributed across the frequency band used. The width and number of channels has to be large enough to accurately reproduce the spectral shape of the emission or absorption received by the radio telescope. Instantaneous channel bandwidths of typically ~1 kHz are used, depending on the scientific program.7

___________________

7 From ECC Report 171, “Impact of Unwanted Emissions of Iridium Satellites on Radioastronomy Operations in the Band 1610.6-1613.8 MHz,” Electronic Communications Committee of the European Conference of Postal and Telecommunications Administrations, Tallinn, Estonia, October 2011.

Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

One challenge for coordinated spectral sharing of this frequency range is that observations in the 1612 MHz band are sometimes conducted on targets of opportunity (e.g., particularly on objects such as comets, which have been observed to produce transient emissions in this line). Observations in the 1612 MHz band are carried out at a number of radio astronomy sites in numerous countries worldwide. In the United States, these include the VLA, the GBT, the Arecibo Observatory, the Allen Telescope Array, and the 10 stations of the Very Long Baseline Array. Internationally, current facilities include the Nancay RadioHeliograph Telescope (France), Jodrell Bank (United Kingdom), MERLIN (United Kingdom), the 100-m Radio Telescope Effelsberg (Germany), the Westerbork Synthesis Radio Telescope (Netherlands), the stations of the European VLBI Network, the Medicina Radio Observatory (Italy), the 64m Parkes Observatory (Australia), the Australia Telescope Compact Array (Australia), the Australian Square Kilometre Array Pathfinder (Australia), the stations of the Australian Long Baseline Array (Australia), MeerKAT (South Africa), FAST (China), the Russian VLBI network (Russia), the RATAN-600 (Russia), the ROT-54/2.6 (Armenia), and the Brazilian Decimetric Array (Brazil).

Recommendation: The committee supports modernization of the Global Maritime Distress Safety Systems as long as radio astronomy operations are protected. There is special concern for new satellite operations because one communication satellite operator in this band has had a history of producing interference (e.g., ECC Report 171: “Impact of Unwanted Emissions of Iridium Satellites on Radioastronomy Operations in the Band 1610.6-1613.8 MHz”). At this time, the satellite operator is replacing the present generation of satellites with new ones that may address this issue. Tests with the new system are expected to be completed before WRC-19. Given the concerns raised, the results of these tests should be taken into consideration before radio regulations relative to this band are adopted.

Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

AGENDA ITEM 1.9.1:
AUTONOMOUS MARITIME RADIO DEVICES

Agenda Item 1.9.1 considers “regulatory actions within the frequency band 156-162.05 MHz for autonomous maritime radio devices to protect the Global Maritime Distress Safety Systems (GMDSS) and automatic identification systems (AIS), in accordance with Resolution 362 (WRC-15).”

The frequency ranges under consideration are 156-162.05 MHz. The devices used for AIS are likely to be low cost, numerous, and primarily deployed in oceans and lakes. Any unlicensed device is a potential interferer if deployed near a radio telescope.

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. These facilities are used for studies of the Sun, 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, being tested at Green Bank and Berkeley and to be built in South Africa. International facilities working in this frequency range include the LOFAR in the Netherlands (with international stations across Europe), the MWA in Australia, the Mauritius Radio Telescope, and the Giant Metrewave Radio Telescope in India. Future facilities that will eventually operate in this frequency range include FAST in China and the low-frequency component of SKA-Low, being planned for Australia. While the geographic locations of most radio facilities should help mitigate the possibility of RFI from GMDSS, if deployed only in maritime environments, care should be taken that aggregate out-of-band emission (OOBE) levels from these devices still conform to the provisions established by ITU-R RA.769, which sets the detrimental interference level as −259 dBW/m2/Hz in this band.

Earth Exploration-Satellite Service

Active techniques in this band are used for ionospheric sounding, noise and absorption measurements, and radio propagation-based techniques (both ground-to-ground and ground-to-space). Incoherent scatter radar provides precise measurement of the thermal ionospheric plasma. Primary measurements include electron

Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

density, electron temperature, ion temperature, and ionospheric drifts and provide information on electric fields, neutral winds, and ion compositions. Typical HF/VHF/UHF/L-band center frequencies, with up to 30 MHz bandwidth on receive and typically up to 1 MHz bandwidth on transmit, are used in existing systems. 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 Astronomy 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.

___________________

8 Portions of this text are taken from National Academies of Sciences, Engineering, and Medicine, Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses: Second Edition, The National Academies Press, Washington, D.C., 2015.

Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

AGENDA ITEM 1.9.2:
MARITIME MOBILE-SATELLITE ALLOCATIONS

Agenda Item 1.9.2 considers “modifications of the Radio Regulations, including new spectrum allocations to the maritime mobile-satellite service (Earth-to-space and space-to-Earth), preferably within the frequency bands 156.0125-157.4375 MHz and 160.6125-162.0375 MHz, to enable a new VHF data exchange system (VDES) satellite component, while ensuring that this component will not degrade the current terrestrial VDES components, applications specific messages (ASM) and automatic identification systems (AIS) operations and not impose any additional constraints on existing services in these and adjacent frequency bands as stated in recognizing d) and e) of Resolution 360 (Rev. WRC-15).”

The frequency ranges under consideration are 156.0125-157.4375 MHz and 160.6125-162.0375 MHz. The committee notes that propagation is largely unimpeded by the atmosphere at these low frequencies. Thus, geographic shielding is less effective in mitigating RFI in these bands.

Radio Astronomy Service

There is a primary allocation to RAS from 150.05-153.0 MHz. Care should be taken that out-of-band emission (OOBE) levels still conform to the provisions established by ITU-R RA.769, which sets the detrimental interference level at −259 dBW/m2/Hz in this band. In particular, at these low frequencies, telescopes have a correspondingly larger primary beam and can be greatly impacted by space-to-Earth transmissions. The typical antennas used at these frequencies have significant receptivity in all directions, and strong interference places difficult demands on the dynamic range of the signal processing systems. Thus, there is significant concern that emissions from satellites will come from high-elevation angles directly into the main beam or sidelobes of radio telescopes.

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. International facilities working in this frequency range include the LOFAR in the Netherlands (with international stations across Europe), the MWA in Australia, the Mauritius

Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

Radio Telescope, and the Giant Metrewave Radio Telescope in India. Future facilities that will eventually operate in this frequency range include FAST in China and the low-frequency component of the SKA-Low, being planned for Australia.

Earth Exploration-Satellite Service

Active techniques in this frequency range are used for ionospheric sounding, noise and absorption measurements, and radio propagation-based techniques (both ground-to-ground and ground-to-space). Incoherent scatter radar provides precise measurement of the thermal ionospheric plasma. Primary measurements include electron density, electron temperature, ion temperature, and ionospheric drifts and provide information on electric fields, neutral winds, and ion compositions. Typical HF/VHF/UHF/L-band center frequencies, with up to 30 MHz bandwidth on receive and typically up to 1 MHz bandwidth on transmit, are used in existing systems. Up to 10 MHz bandwidth is planned for future systems. The Irkutsk incoherent scatter radar currently operates at these frequencies.9

Recommendation: Any spectrum allocation should be done in such a way so as to preserve access of the Radio Astronomy Service and the Earth Exploration-Satellite Service to the bands allocated to them, including appropriate spectral separations that conform to interference criteria provided by ITU-R RA.769 and ITU-R RS.2017. This is particularly important since in many cases, at these frequencies, satellite transmissions will be made directly into the main beam of the individual 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.

___________________

9 Portions of this text are taken from National Academies of Sciences, Engineering, and Medicine, Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses: Second Edition, The National Academies Press, Washington, D.C., 2015.

Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

AGENDA ITEM 1.13:
FUTURE DEVELOPMENT OF INTERNATIONAL MOBILE TELECOMMUNICATIONS

Agenda Item 1.13 considers “identification of frequency bands for the future development of International Mobile Telecommunications (IMT), including possible additional allocations to the mobile service on a primary basis, in accordance with Resolution 238 (WRC-15).”

The frequency bands proposed in Resolution 238 (WRC-15) for future development of IMT applications include 24.25-27.5 GHz, 31.8-33.4 GHz, 37.0-40.5 GHz, 40.5-42.5 GHz, 42.5-43.5 GHz, 45.5-47 GHz, 47-47.2 GHz, 47.2-50.2 GHz, 50.4-52.6 GHz, 66-76 GHz, and 81-86 GHz. As a general technical note applicable to all proposed new frequency allocations, care must be taken in assessment of the impact on incumbent RAS and EESS bands. Absence of detectable emissions does not imply that the frequencies are not in use by the passive service. While RAS bands can be protected regionally by limiting emissions within a certain radius of a facility, this is not the case with EESS observations, which are typically satellite based and global in nature. Almost all of the frequency ranges under consideration here are adjacent to, or congruent with, EESS and RAS passive allocations. Of particular concern for RAS and EESS are possible new primary allocations to IMT at 31.8-33.4 GHz and 40.5-42.5 GHz, which are adjacent to primary allocations to the passive services.

The discussion below includes text from comments filed by the Committee on Radio Frequencies in response to the Federal Communications Commission (FCC) Notice of Inquiry (October 2014),10 Notice of Proposed Rulemaking (October 2015),11 and Further Notice of Proposed Rulemaking (July 2016)12 on a similar topic. 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.

11 FCC Dockets GN 14-177, IB 15-256, RM-11664, WT 10-112, and IB 97-95.

12 FCC Dockets GN 14-177, IB 15-256, RM-11664, WT 10-112, and IB 97-95

Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

Radio Astronomy Service

In general, radio observatories that operate above 24 GHz are located in remote, high, and dry sites, where signal attenuation is due only to the inverse square law with little atmospheric attenuation, even at high frequencies. Thus, consideration of RFI to RAS must include analysis appropriate to the geographic location of the observatory. In the United States, these observatories include the VLA (New Mexico), the GBT (West Virginia), the Haystack Observatory (Massachusetts), Owens Valley (California), the 10 sites included in the Very Long Baseline Array, and the 12m ALMA prototype antenna located at Kitt Peak (Arizona). Internationally, these include the Large Millimeter Telescope (Mexico); the Mopra and the Australian Telescope Compact Array in Australia; the Nobeyama 45m Telescope and Nobeyama Millimeter Array in Japan; the 100-m Radio Telescope Effelsberg in Germany; the IRAM 30m in Spain; the ALMA prototype antenna recently deployed to Greenland; the Atacama Large Millimeter Array (ALMA) in Chile; the Plateau de Bure Interferometer (and the planned expansion of PdBI to NOEMA) in France; the Onsala 20m telescope in Sweden; the 10 stations of the European VLBI Network (EVN), including Medicina, Noto, and Sardinia in Italy, Metsahovi in Finland, and Yebes in Spain; the Korean VLBI Network (KVN) in Korea; DASI at the South Pole; the Delingha Observation Station and the planned Qitai Radio Telescope in China; the RATAN-600, Galenki RT-70, and 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), including the harmonics of mobile devices. Full consideration of the impact of new allocations must include the possibility of OOBE and the sum of aggregate emissions from multiple devices.

24 GHz Band

The frequency range 23.6-24.0 GHz is protected by RR 5.340 (no transmissions are permitted) and is 250 MHz from the lower edge of the frequency range under consideration. The protected band includes spectral line transitions associated with ammonia at 23.694, 23.723, and 23.870 GHz, which is observed in molecular clouds in the Milky Way. Any use of the lower frequencies in the range allocated for IMT (i.e., those just above 24.0 GHz) must include measures to protect the 23.6-24.0 GHz RAS band from OOBE.

Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

31 GHz Band

For RAS, the primary allocation at 31.3-31.5 GHz (and also 31.5-31.8 GHz in Region 2) is vitally important for continuum measurements because it lies near the minimum in atmospheric absorption in this part of the spectrum. Combined with measurements in other bands at approximately octave intervals, such measurements provide information on the broad spectrum of astronomical radio sources, such as supernovae, pulsars, radio galaxies, and quasars. The detrimental interference level for this band is −228 dBW/m2/Hz, averaged across the full 500 MHz width of the band (ITU-R RA.769, Table 1), and as such, careful filtering will be required for the proposed adjacent IMT allocation at 31.8-33.4 GHz.

37/42 GHz Bands

Of primary concern for RAS is that there is a primary allocation at 42.5-43.5 GHz that is congruent with, and adjacent to, several of the frequency ranges under consideration for IMT (e.g., the proposed new primary allocation of 40.5-42.5 GHz and the existing co-primary allocation at 42.5-43.5 GHz). This frequency band is protected such that administrations should take all practicable steps to protect RAS from harmful interference (ITU RR 5.149). Spectral line emission of SiO at 42.519, 42.821, 43.122, and 43.424 GHz are among those of greatest importance to radio astronomy.13 This frequency band is important for detection of strong SiO maser emissions from stars and star-forming regions. 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). Careful studies will be required to determine whether mobile and/or fixed point-to-point services in the 42 GHz band can be consistent with protection of the RAS in the 42.5-43.5 GHz band.15

___________________

13 See International Telecommunication Union (ITU) Radiocommunications Bureau, Handbook on Radio Astronomy, Third Edition, http://www.itu.int/pub/R-HDB-22, 2013, p. 37, Table 3.2.

14 Ibid., p. 35, Table 3.1.

15 From CORF Comments to the FCC in GN Docket No. 14-177; IB Docket No. 15-256; RM-116640; WT Docket No. 10-112; and IB Docket No. 97-95; filed March 16, 2016.

Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

Furthermore, pursuant to ITU RR 5.149, radio observatories are protected from interference in the frequency range 36.43-36.5 GHz, which is used to observe spectral line emission from methanol (36.169 GHz) located in molecular clouds in the Milky Way. This frequency range falls within the EESS passive band window at 36-37 GHz. Thus, OOBE from IMT allocations at 37.0-40.5 GHz are of concern for RAS as well.

47/50 GHz Bands

A very narrow spectral window is allocated to RAS within the frequency ranges of interest. Specifically, pursuant to ITU RR 5.149, radio astronomy observatories are protected from interference in the frequency range 48.94-49.04 GHz. Furthermore, to protect radio astronomy, all airborne emissions are prohibited in this frequency range (ITU RR 5.340), which is used to observe spectral line emission from carbon monosulfide in molecular clouds. Since this RAS allocation falls within the IMT allocation of 47.2-50.2 GHz, care must be taken to retain the protections for RAS, including the restrictions on airborne use of the narrow RAS frequency allocation.

In addition, due to the potential for OOBE arising from harmonics, there are also significant concerns about this and other IMT allocations between 45.5 and 52.6 GHz (45.5-47 GHz, 47-47.2 GHz, and 50.4-52.6 GHz). Specifically, all emissions are prohibited in the frequency ranges of 86-92 GHz and 100-102 GHz (ITU RR 5.340), which correspond to frequencies associated with the first harmonic of these IMT allocations. Furthermore, radio astronomy has primary allocations, and radio observatories are to be protected from harmful interference (ITU RR 5.149), in the frequency ranges of 92-94 GHz, 94.1-95 GHz, and 95-100 GHz. Thus, consideration of IMT applications at this frequency band should take into account the feasibility of dampening the harmonics from mobile devices to meet the low emission levels required to protect RAS.

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), and all emissions are prohibited from 86-92 GHz (ITU RR 5.340). For the latter, the detrimental levels for continuum and spectral line radio astronomy observations are −228 dBW/m2/Hz and −208 dBW/m2/Hz for the average across

Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

the full 6 GHz band and the peak level in any single 1 MHz channel (ITU-R RA.769, Tables 1 and 2, respectively). 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. Thus, the signal attenuation with distance is due only to the inverse square law, with some small atmospheric attenuation.

Indeed, because there is relatively little absorption from atmospheric O2 and H2O at these frequencies, these bands constitute some of the most important high-frequency ranges for both continuum and line observations of celestial objects.16 The growing understanding of star formation and stellar evolution is critically dependent on millimeter wave observations. In addition, highly red-shifted galaxies can be detected over the full range of the RAS allocations. Furthermore, a new scientific field, astrochemistry, has arisen from the discovery of a very wide range of complex molecules in space. It is essential that the protection presently available to radio astronomy observatories remain in place.

Earth Exploration-Satellite Service

ITU-R-RS.2017 defines interference criteria for all EESS passive satellites. For the bands in question, consideration of OOBE is particularly important for the mobile communication bands that are proposed adjacent to passive Earth remote sensing bands. Specifically, it is imperative that any proposed IMT bands include spectral separation (guard bands) to protect the incumbent users of the passive bands, who have designed and developed EESS missions without the expectation of mobile communications in such close spectral proximity. These incumbent EESS missions represent billions of dollars in development and deployment of instruments and satellites. Most incumbent passive EESS users at 24, 31.5, and 37 GHz operate in a direct detection (homodyne) mode with limited protection against OOBE. In direct detection, band definition is achieved with filters that are limited by the properties of the materials used in the filter itself. For a given material, the bandwidth of a filter is proportional to the central frequency, so the width of the necessary guard bands to suppress emissions to a desired level also increases in proportion to the frequency. In other words, proportionally larger guard bandwidths are needed as the frequency increases. Furthermore, for the same reasons, it is likely that mobile devices with limited size and cost will not be able to adequately filter their OOBE

___________________

16 See ITU, Handbook on Radio Astronomy, supra note 3, Tables 3.1 and 3.2.

Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

to meet the stringent requirements of the adjacent passive bands. Creating guard bands proportional to the operating frequency is the only way to protect the incumbent EESS applications that are vital for global weather forecasting and climate research. Passive satellite missions operating in the bands in question are enumerated in Table 2.3.

24 GHz Band

The frequency range 23.6-24.0 GHz is protected by ITU RR 5.340 (no transmissions are permitted) 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. This band is extremely important for forecasting the weather and is used oper-

TABLE 2.3 EESS (Passive) Satellite Missions Relevant to Agenda Item 1.13

Sensor Satellite Center Frequency (GHz) Bandwidth (MHz)
AMSR2 GCOM-W1 23.8, 36.5, 89 400, 1000, 3000
AMSU-A, ATMS NOAA-15, NOAA-18, NOAA-19, MetOp-A, MetOp-B, Suomi NPP 23.8, 31.4, 50.3, 51.76, 52.8, 89.5 270, 180, 180, 400, 400, 5000
GMI GPM 23.8, 36.5, 89 400, 1000, 6000
PMR WindSat 23.8, 37a 500, 2000
AMR-2 Jason-2 and Jason-3 23.8
MWI MetOp-SG 23.8, 31.4, 50.3, 52.61, 89 400, 200, 400, 400, 4000
MADRAS Megha-Tropiques 23.8, 36.5, 89 200, 500, 1350
MTVZA-GY Meteor-M 23.8, 31.5, 36.7, 42, 48, 52.8 400, 400, 400, 400, 400, 400
MWRI FY-3 23.8, 36.5, 89 400, 1000, 6000
MWRI’ HY-2A 23.8, 37 400, 1000
SSM/I, SSMIS DMSP-F15, -F16, -F17, -F18, -F19 22.2, 37a, 50.3b, 52.8b, 85.5 401, 1600, 380, 389, 1500

NOTE: Acronyms are defined in Appendix B.

a Department of Defense satellites operate outside the passive protected band and into a shared government use band.

b Not every instrument in the list has every channel. SSMIS has the full channel suite.

Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

ationally by many nations. Any use of the lower frequencies in the proposed range for IMT (i.e., those just above 24.0 GHz) must include measures to protect the 23.6-24.0 GHz EESS band.

31 GHz Band

The two primary EESS (passive) allocations of concern in this frequency range are (1) 31.3-31.5 GHz, in which all emissions are prohibited, and (2) 31.5-31.8 GHz, in which all emissions are prohibited in Region 2 (ITU RR 5.340). The protected 31.3-31.8 GHz frequency band is used by a variety of satellites for weather forecasting, notably the ATMS instrument on the National Oceanic and Atmospheric Administration (NOAA)/NASA Suomi National Polar-orbiting Partnership (NPP) satellite and the AMSU-A instruments on NOAA 15, 18, and 19 satellites as well as the European MetOp A and B satellites. 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. Indeed, the typical 3 dB band edge for Earth remote sensing instruments is only 10 MHz from the proposed IMT band. Thus, guard band protection is required to preserve the incumbent use by EESS. For example, a single 1 W isotropic radiator at 31.3 GHz results in an equivalent thermal signal of 30 K and will need to be rejected at >20 dB to not be seen by NASA/NOAA’s ATMS.17 Similarly, for mobile applications, 1,000 devices operating in that band will need to be rejected by >50 dB.

37/40 GHz Bands

There is an important primary EESS allocation at 36-37 GHz that is used by many agencies and is adjacent to the 37.0-40.5 GHz band under discussion for IMT applications. This band offers the largest

___________________

17 The ATMS instrument is the next-generation cross-track microwave sounder providing atmospheric temperature and moisture measurements for operational weather and climate applications. ATMS is a key instrument that collects microwave radiation measurements from Earth’s atmosphere and surface all day and all night, even through clouds. ATMS currently flies on the Suomi NPP satellite mission and will fly on the JPSS-1 and JPSS-2 satellite missions. See National Oceanic and Atmospheric Administration, Joint Polar Satellite System, “Advanced Technology Microwave Sounder (ATMS),” http://www.jpss.noaa.gov/atms.html.

Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

contiguous bandwidth between the 23 GHz water line and the 60 GHz oxygen line complex. Because this bandwidth affords unmatched radiometric sensitivity, scientific applications are found in a range of environmental conditions, including atmospheric water vapor, precipitation, cloud properties, freeze/thaw conditions, snow, sea ice, sea-surface temperature, ocean vector winds, and ocean topography (tracing conditions such as El Niño).18 The data obtained by satellite observations are assimilated into global circulation models and affect directly the quality of weather forecasting.

Earth remote sensing observations are conducted with instruments on satellites such as the NASA Global Precipitation Measurement Mission’s Microwave Imager, the Department of Defense (DOD) Special Sensor Microwave/Imager and WindSat instruments, and the Japan Aerospace Exploration Agency Global Change Observation Mission-Water 1’s Advanced Microwave Scanning Radiometer 2. As described above, many of these sensors operate in direct detection mode, and their ability to reject OOBEs is limited by basic physics. 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. Furthermore, with lower orbits and larger receiver antennas, these EESS passive sensors are far more susceptible to terrestrial interference than the ATMS described above. With multiple interfering sources, assuming the sources are incoherent, the interfering powers received at the satellite add directly; with, say, 1,000 interfering mobile sources, the interference level will be increased by 30 dB. OOBE rejection levels need to be increased by 16 dB over the ATMS levels specified above to >36 dB and >66 dB rejection for a single mobile device and 1,000 mobile devices, respectively. It would therefore be prudent to include spectral separation (guard bands) designed to match the incumbent users’ filter response in order to preserve these expensive and important assets. Alternatively, dynamic allocation of frequencies could be mandated to avoid interfering with the satellite receptors when the footprint of the satellite crosses terrain, as determined by ephemerides and instrument beam.

___________________

18 See NASA, “Global Precipitation Mission,” last updated August 3, 2017, http://www.nasa.gov/mission_pages/GPM/spacecraft/; NASA, “TMI,” http://pmm.nasa.gov/node/161; Jet Propulsion Laboratory, “SSM/I,” http://podaac.jpl.nasa.gov/SSMI; and NOAA, “Sensors—WindSat Overview,” https://www.star.nesdis.noaa.gov/mirs/windsat.php.

Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

47/50 GHz Bands

The IMT allocation at 50.4-52.6 GHz band is placed directly between two passive bands used for microwave temperature sounding. Specifically, all emissions are prohibited for 50.2-50.4 GHz and 52.6-54.25 GHz (ITU RR 5.340). In addition, with the IMT allocation at 47.2-50.2 GHz, the lower of these two bands will be completely surrounded by active users (see also Agenda Item 1.6). These EESS allocations are used by an international suite of weather satellites (see Table 2.3). The instruments aboard these satellites operate on the edge of the 58-59 GHz oxygen line complex and are used to measure temperature as a function of altitude. The data obtained from these instruments are used to initialize global and regional weather forecast models and therefore have a large impact on the ability to forecast weather events, including life-threatening and costly extreme weather events. Because this band is far from the center of the oxygen line complex, observations penetrate deep into the atmosphere with little atmospheric attenuation. This makes these bands susceptible to RFI, and care must be taken to protect them. As with several of the other instruments described above, guard bands must be provided, accounting for technological limitations of both the incumbent receivers and the proposed transmitters to adequately protect weather forecast ability. It should be noted that when combined with proposed services at 47.2-50.2 GHz, the EESS (passive) allocation at 50.2-50.4 GHz would be completely surrounded by active users.

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). This band is used by satellite-based instruments such as the NOAA AMSU-A, AMSU-B, and ATMS; NASA’s Global Precipitation Measurement Mission’s Microwave Imager (GMI); the DOD’s SSMI and SSMI/S; and the AMSR2 instruments. The primary data product from these observations is a measurement of precipitation (from cloud ice scattering), which is widely used to provide real-time imagery for weather forecasting (such as NOAA’s NexRad system).19 The frequency range used tends to be quite broad in order to reduce the effect of the higher receiver noise at these frequencies. As such, this band is also highly susceptible to OOBE

___________________

19 See NOAA, “NWS Southern Region Headquarters,” http://www.weather.gov/srh/sod/radar/radinfo/radinfo.html.

Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

and, being at a higher frequency and having a large bandwidth, will require an even larger spectral allocation for guard banding to preserve the incumbent EESS applications.

Recommendation: While the committee recognizes the need to share spectral frequencies, care should be taken in the assessment of the impact on incumbent Radio Astronomy Service (RAS) and Earth Exploration-Satellite Service (EESS) bands, particularly with regard to spectral separation. In all cases, it is critical that the limits of out-of-band emissions into the RAS and EESS bands must comply with ITU-R RA.769 (Tables 1, 2, and 3) and ITU-R RS.2017 (Table 1), 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.

Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

AGENDA ITEM 1.14:
HIGH-ALTITUDE PLATFORM STATIONS

Agenda Item 1.14 considers “on the basis of ITU-R studies in accordance with Resolution 160 (WRC-15), appropriate regulatory actions for high-altitude platform stations (HAPS), within existing Fixed-Service allocations.”

As summarized in Resolution 160, current allocations to HAPS include the following: 1885-1980 MHz (global), 2010-2025 MHz (Regions 1 and 3), 2110-2170 MHz (Regions 1 and 3), 2110-2160 MHz (Region 2), 6440-6520 MHz (HAPS-to-ground; five countries, RR 5.457), 6560-6640 MHz (ground-to-HAPS; five countries, RR 5.547), 27.9-28.2 GHz (fixed downlink; Regions 1 and 3), 31.0-31.3 GHz (fixed uplink; Regions 1 and 3), 47.2-47.5 GHz (global), and 47.9-48.2 GHz (global). Resolution 160 proposes harmonizing these frequency allocations at the global or regional level and also considers the use of 38-39.5 GHz (global), 21.4-22 GHz (Region 2), and 24.25-27.5 GHz (Region 2) for HAPS. While there are no RAS or EESS science applications directly in the bands given in Resolution 160, several of the bands are either adjacent to bands allocated to the passive services or may have harmonics that fall within bands for which administrations are also urged to take all practical steps to protect the passive services from harmful interference (RR 5.149) or for which all emissions are prohibited (RR 5.340). Furthermore, for 23 countries, RR 5.543A specifies additional emission level limits for HAPS systems using the 31.0-31.3 GHz band in order to protect the adjacent passive services band (31.3-31.8 GHz) 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) because terrain shielding cannot block emissions originating at high altitude. Thus, suppression of out-of-band emission (OOBE) in the adjacent or harmonic frequencies is a critical concern for compatibility of HAPS with existing services because they may be in direct line of sight to a radio observatory. Of further concern is that HAPS are likely to serve rural and remote regions—precisely the geographic considerations that are favorable for sites of radio astronomy observatories. In the United States, radio astronomy facilities that observe at these frequencies include the GBT, the VLA, and the 10 stations of the Very Long Baseline Array.

Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

Of the existing HAPS allocations summarized in Resolution 160, the 31.0-31.3 GHz (fixed uplink, Regions 1 and 3) is of concern to RAS due to the possibility of in-band emissions at 31.2-31.3 GHz (ITU RR 5.149) and OOBE, particularly in the adjacent frequency allocation of 31.3-31.5 GHz, for which all emissions are prohibited (RR 5.340). 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). In addition, the first harmonic of the 47.2-47.5 GHz (global) and 47.9-48.2 GHz (global) allocations fall within a spectral band (94.1-100 GHz) for which administrations are urged to take all practicable steps to protect the RAS from harmful interference (RR 5.149). This frequency range is used by radio astronomers for observations of complex molecules that provide information on protoplanetary systems, star formation, and the origins of life. In addition, this frequency range is used for broadband continuum observations of a variety of radio sources.

Of the proposed new HAPS allocations summarized in Resolution 160, both the 38-39.5 GHz (global) and 21.4-22 GHz (Region 2) allocations are of particular concern to RAS due to the possibility of OOBE in the first harmonic, which fall in spectral bands (76-86 GHz and 42.5-43.5 GHz, respectively) for which administrations are urged to take all practicable steps to protect RAS from harmful interference (RR 5.149). The 21.4-22 GHz region is also adjacent to 22.01-22.5 GHz, for which administrations are urged to take all practicable steps to protect RAS from harmful interference (RR 5.149). These spectral windows correspond to regions rich with molecular transitions and are also preferred regions for continuum observations of radio sources (see also Agenda Item 1.13).

Earth Exploration-Satellite Service

Of the existing HAPS allocations summarized in Resolution 160, the 31.0-31.3 GHz (fixed uplink in Regions 1 and 3) is of particular concern to EESS due to the possibility of OOBE in the adjacent frequency allocation of 31.3-31.5 GHz, for which all emissions are prohibited (RR 5.340). This frequency range is used by a variety of weather satellites for weather forecasting (see also Agenda Item 1.13). In addition, the 27.9-28.2 GHz allocation (fixed downlink; Regions 1 and 3) is of concern because the first harmonics fall within the EESS band at 55.78-56.26 GHz within which, to protect the EESS passive service in this band, the maximum power density delivered by a transmitter to the antenna of a fixed-service station is limited to

Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

−26 dB W/MHz (RR 5.557). This frequency range is used to measure the atmospheric temperature profile.

Of the proposed new allocations, the 21.4-22 GHz region is of concern because it is adjacent to an EESS allocation that is used to measure precipitable water and to study the freeze/thaw transition. In addition, the proposed allocation of 24.25-27.5 GHz is only 250 MHz from the edge of the EESS band at 23.6-24.0 GHz, for which all emissions are prohibited (RR 5.340). This protected band is intended to cover a water vapor absorption line (see also Agenda Item 1.13). In addition, the first harmonic of this frequency allocation falls within the EESS band at 50.2-50.4 GHz (see also Agenda Item 1.13).

Recommendation: Compatibility studies should be made to ensure the protection of the Radio Astronomy Service and the Earth Exploration-Satellite Service from unwanted emissions of high-altitude platform stations links. The limits defined by ITU-R RA.769 should be met under all conditions. In addition, if allocations are extended to other administrations not currently listed in RR 5.543A, they should be included in it.

Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

AGENDA ITEM 1.15:
275-450 GHZ

Agenda Item 1.15 considers “identification of frequency bands for use by administrations for the land-mobile and fixed services applications operating in the frequency range 275-450 GHz, in accordance with Resolution 767 (WRC-15).”

As noted in Resolution 767 (WRC-15), the current Table of Frequency Allocations does not allocate bands above 275 GHz, but a number of bands have been identified for use by passive services within this frequency range. Specifically, RR 5.565 identifies spectral regions for both RAS and EESS (passive) but does not preclude use of these bands by active services. Rather, administrations are urged to take all practicable steps to protect the passive services in these identified bands.

Use of the frequency range 275-3000 GHz was discussed previously as Agenda Item 1.6 of the WRC-12. It is important to note that in the intervening years since this spectral range was discussed at the WRC, the importance of receive-only scientific use of this frequency range has become even more evident, particularly with the new discoveries enabled by the world’s most powerful millimeter/submillimeter telescope—ALMA in Chile. 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 submillimeter 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 National Academy of Engineering on Agenda Items at Issue at the World Radiocommunication Conference 2012, The National Academies Press, Washington, D.C., 2013.

21 The theory of quantum mechanics dictates that the rotational motion of molecules is characterized by discrete energy levels. When a molecule changes energy levels, it makes a transition, either emitting or absorbing a photon at a frequency proportional to the energy difference between the two levels. The emission at these specific frequencies therefore allows scientists to study their concentration in the region under study.

Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

TABLE 2.4 Selected Spectral Lines between 275 and 450 GHza

Spectral Line Transition Frequency (GHz) Significance
CO 3-2
4-3
345
461
Important tracer of galactic and extragalactic structure
Probe of star-forming regions and protoplanetary disks
HCO+ 4-3
5-4
356
446
Probe of high-density regions, protostellar cores
HCN 4-3
5-4
354
443
Probe of high-density regions, protostellar cores, Inner shells of evolved stars
CS 6-5
7-6
8-7
9-8
293
342
392
440
Dense protostellar cores, evolved stars, planetary nebulae
H3O+ 1(1)-2(1)
2(1)-3(1)
307
388
Oxygen chemistry, leading to H2O, OH, O2
HDO 6(2,5)-5(3,2) 314 Probe of D/H isotope ratio
H2D+ 1(1,0)-1(1,1) 372 Probe of D/H isotope ratio, chemical fractionation
O2 (3,2-1,2) 425 Interstellar coolant, origins of life
Metal hydrides (SiH, LiH, MgH, NaH, AlH) 1-0
2-1
3-2
Etc.
Various Interstellar coolants Building blocks of interstellar chemistry

a To observe the listed transitions, fractional bandwidths of 1 percent are required for observations of the Milky Way galaxy. Larger bandwidths are needed for extragalactic measurements on the low-frequency side because of the Doppler shift caused by the recessional velocities of distant objects in the universe—for example, a 10 percent bandwidth is required to cover the nearby clusters of galaxies of which our Milky Way galaxy is a member.

Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

radio spectrum has expanded greatly in recent years. In addition to ALMA and the Atacama Pathfinder Experiment (APEX), both located in Chile, radio astronomy observations at these frequencies are also obtained with the James Clark Maxwell Telescope (JCMT) and the Submillimeter Array (SMA), both located in Hawaii; the Submillimeter Telescope (SMT) of the Arizona Radio Observatory; the Large Millimeter Telescope in Mexico; the IRAM 30m in Spain; the Solar Submillimeter Telescope and the planned Large Latin American Millimeter Array (LLAMA) in Argentina; the Suffa RT-70 radio telescope in Russia; the NOEMA array in France; and the South Pole Telescope (SPT).

In many situations, band protection for radio astronomy can be accomplished with geographic isolation of observatories. As discussed in ITU-R RA.2189, this is particularly relevant at high frequencies due to the reduced atmospheric transmission above 275 GHz (see Figure 2.1). However, by necessity, radio astronomy facilities observing at these high frequencies are located at sites with typically low atmospheric attenuation (i.e., dry sites at high altitudes) and usually with very little geographic shielding. Each observatory site experiences a variety of physical conditions that affect propagation models, including a range of humidity and temperature. Thus,

images
FIGURE 2.1 Atmospheric transmission fraction at the Atacama Large Millimeter Array (ALMA) site as a function of frequency for three different column densities of precipitable water vapor. The vertical colored banding indicates the frequency ranges of the ALMA bands, which are labeled at the top (3 through 10). The frequency ranges under consideration here correspond to ALMA bands 7 and 8. SOURCE: ALMA Observation Support Tool (OST) Help Documentation, http://almaost.jb.man.ac.uk/help/.
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

multiple propagation models must be developed to inform the appropriate separation and power limitations on spectrum uses at these frequencies for each site. Furthermore, because of the frequencies involved at every stage of signal processing, damaging interference from lower-frequency spectrum uses can also be amplified and introduced into high-frequency detectors. Thus, protection from RFI across the spectrum at these geographically isolated sites is critical.

The 275-450 GHz region encompasses several spectral windows that are used for ground-based astronomy: 275-323 GHz, 327-371 GHz, 388-424 GHz, and 426-442 GHz (see Figure 2.1). In this frequency range, many of the common interstellar molecules such as CO, HCN, HCO+, and CS have their higher-energy rotational transitions (see Table 2.4). Because these spectral lines trace relatively hot (T > 200 K) and dense (n > 107 cm−3) gas, they are important probes of the interstellar medium, where stars form. These transitions also trace circumstellar gas close to the stellar photosphere and can be used to elucidate the physical processes associated with evolved stars, including mass loss and photospheric shocks. In addition, these molecules are also of great significance for the investigation of the roles of organic molecules in the origin of solar systems, planets, and life.22

Due to the expansion of the universe, observations of higher-frequency molecular transitions can be shifted into these frequency bands. Thus, observations in these spectral windows provide insight into the formation and assembly of galaxies in the early universe, the evolution of large-scale structure in the universe, and the evolution of the powerful active nuclei in the centers of galaxies as a function of cosmic time.

One clear indication of the scientific importance of these high-frequency spectral windows is that almost 50 percent of the scientific observations with ALMA are conducted in the 275-450 GHz range. These include studies of the reionization era, otherwise known as the cosmic dawn. In particular, ALMA’s line sensitivity and spatial resolution have allowed it to image emission from distant [C II], [N II], and [O III] in galaxies forming in the early universe. Indeed, at the time of this writing, the most distant detection of oxygen in the universe comes from observations of the 88 micron line of [O III] redshifted (z = 7.212) 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.

23 A.K. Inoue, Y. Tamura, H. Matsuo, K. Mawatari, I. Shimizu, T. Shibuya, K. Ota, et al., Detection of an oxygen emission line from a high-redshift galaxy in the reionization epoch, Science 352:1559-1562, 2016.

Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

emitted from a galaxy at an epoch of only about 700 million years after the Big Bang and therefore provides insight into the physical properties and elemental abundances of the interstellar medium in the early universe.

The stable atmosphere in this spectral range also makes it possible to obtain extremely high-spatial-resolution images with ALMA. For example, with ALMA’s long baseline configuration, observations of a strongly gravitationally lensed submillimeter galaxy were obtained with an angular resolution of 23 milliarcsecond (mas) at 290 GHz, an order of magnitude improvement over previous observations.24 With the additional magnification provided by the gravitational lens, this angular resolution corresponds to a linear spatial scale of only a few tens of parsecs for this galaxy at a redshift of 3.042. High-spatial-resolution continuum and line observations of such gravitationally lensed sources reveal the physical conditions and distributions of dust and gas in these star-forming galaxies and, therefore, provide significant insight into the evolution of galaxies as a function of cosmic time.

The most highly cited ALMA results are on protoplanetary and transition disks. In the 275-450 GHz frequency range, observations of the CO 4-3 line at 308 GHz can image the “snow line” in many disks, a critical transition region beyond which volatile molecules such as water, ammonia, and carbon monoxide condense into solid ice grains. These grains then accrete to form planetesimals and, eventually, planets. 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. Understanding the physical conditions of these protoplanetary disks and their evolution are critical to studies of the formation of planets and life in the universe.

___________________

24 ALMA Consortium, The 2014 ALMA Long Baseline Campaign: Observations of the strongly lensed submillimeter galaxy HATLAS J090311.6+003906 at z = 3.042, The Astrophysical Journal Letters 808(1):L4, 2015.

25 S.M. Andrews, D.J. Wilner, Z. Zhu, T. Birnstiel, J.M. Carpenter, L.M. Pérez, X.-N. Bai, K.I. Öberg, A.M. Hughes, A. Isella, and L. Ricci, Ringed substructure and a gap at 1 au in the nearest protoplanetary disk, The Astrophysical Journal Letters 820(2):L40, 2016.

Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

Earth Exploration-Satellite Service

The 275-450 GHz band is used by EESS (passive) primarily for atmospheric measurements at frequencies within the atmospheric windows (see Figure 2.2 and Table 2.5), where opacity, and therefore atmospheric propagation, is minimum. Hence, the “protection” from atmospheric propagation is minimal at these frequencies and potential risk of data contamination from RFI is larger. 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. For example, three-dimensional (3D) mapping of ozone in the stratosphere, polar stratospheric clouds, and chlorine sources is used to understand ozone distribution and mechanisms for its

images
FIGURE 2.2 Atmospheric zenith opacity in the radio spectrum commonly used for the Earth Exploration-Satellite Service. The frequency ranges under consideration here include both atmospheric absorption bands and transparent windows. SOURCE: A.J. Gasiewski and M. Klein, The sensitivity of millimeter and submillimeter frequencies to atmospheric temperature and water vapor variations, Journal of Geophysical Research Atmospheres 13:178481-178511, 2000, copyright 2001 by the American Geophysical Union.
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

TABLE 2.5 Representative Passive Sensing Bands and Their Associated Measurements in 275-450 GHza

Frequency (GHz) Bandwidth (MHz) Spectral Line(s) (GHz) Measurement (GHz) Existing or Planned Instrument(s)
275-285.4 10 400 276.33 (N2O), 278.6 (ClO) Window (276.4-285.4) for N2O, ClO, NO
296-306 10 000 Window for 325.1, 298.5 (HNO3), 300.22 (HOCl), 301.44 (N2O), 303.57 (O3), 305.2 (HNO3), 304.5 (O17O) Wing channel for temperature sounding

Window (296-306) for N2O, O3, O17O, HNO3, HOCl
MASTER
313.5-355.6 42 100 {318.8, 345.8, 344.5} (HNO3), 313.8 (HDO), {321.15, 325.15} (H2O), {321, 345.5, 352.3, 352.6, 352.8} (O3), {322.8, 343.4} (HOCl), 345.8 (CO), {345.0, 345.4} (CH3Cl), 345.0 (O18O), 354.5 (HCN), 349.4 (CH3CN), {315.8, 346.9, 344.5, 352.9} (ClO), 351.67 (N2O), 346 (BrO) Water vapor sounding, cloud ice, wing channel for temperature sounding

Window (339.5-348.5) for H2O, CH3Cl, HDO, ClO, O3, HNO3, HOCl, CO, O18O, HCN, CH3CN, N2O, BrO
TWICE, ICI, STEAM-R, CIWSIR, MASTER, MWI, GOMAS, GEM, CAMLS
361-365 4 000 364.32 (O3) Wing channel for water vapor sounding for O3 GOMAS
369.2-391.2 22 000 380.2 (H2O) Water vapor sounding TWICE, GEM, GOMAS
397-399 2000 Water vapor sounding GOMAS
409-411 2000 Temperature sounding
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
416-433.46 17 460 424.7 (O2) Temperature sounding GEM, GOMAS
439.1-466.3 27 200 {443.1, 448} (H2O), 443.2 (O3), 442 (HNO3) Water vapor profiling, cloud ice

Window (458.5-466.3) for O3, HNO3, N2O, CO
ICI, MWI, CIWSIR

NOTE: Acronyms are defined in Appendix B.

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.

Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

depletion. Cloud ice and frozen precipitation are key variables in understanding Earth’s energy budget, water cycle, and the effect of cloud feedback on climate. The upper troposphere and stratospheric water vapor are key aspects of the water cycle and are important for determining climate feedback effects on radiative forcing in the presence of increasing greenhouse gases. The stratosphere temperature measurements provide 3D mapping of the temperature for understanding atmosphere dynamics. Research on chemical composition in the upper troposphere is used for understanding the distribution and transport of pollutants. In addition, observations of trace gases provide a 3D mapping of key atmospheric constituents (e.g., CO, HCl, BrO, N2O) tied to the carbon cycle, global climate, pollution, and atmospheric transport.26 This is vital for potential tracking of chemical or biological weapons of mass destruction in the atmosphere.27Table 2.5 provides a list of frequency bands that are associated with these applications.

Recommendation: The committee urges administrations to protect the passive services from harmful interference, particularly those bands in use by the Atacama Large Millimeter/Submillimeter Array (275-375 GHz, 385-500 GHz, 602-720 GHz, and 787-950 GHz) and the Earth Exploration-Satellite Service (EESS) (passive) applications. Atmospheric propagation models should include the physical conditions for radio observatories located in high, dry sites to appropriately assist in assessing the impact of spectrum allocations on passive scientific uses. No changes should be made to the ITU Radio Regulations unless acceptable sharing and compatibility criteria are developed to ensure the protection of the Radio Astronomy Service and EESS (passive) from future services and applications above 275 GHz.

___________________

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 Destruction, Chapter XII in Joint Warfighting Science and Technology Plan, http://www.nti.org/media/pdfs/35_8.pdf?_=1318280270, and D. Imbro, A national strategy against terrorism using weapons of mass destruction, Science and Technology Review, January/February 1998, https://str.llnl.gov/str/Imbro.html.

Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

AGENDA ITEM 1.16:
WIRELESS ACCESS BETWEEN 5150 AND 5925 MHZ

Agenda Item 1.16 will “consider issues related to wireless access systems, including radio local area networks (WAS/RLAN), in the frequency bands between 5150 MHz and 5925 MHz, and take the appropriate regulatory actions, including additional spectrum allocations to the mobile service, in accordance with Resolution 239 (WRC-15).”

Resolution 239 specifically mentions that EESS missions (current and planned) in this band are used for reliable and up-to-date information on how Earth and its climate are changing and recognizes that sharing 5350-5470 MHz between EESS (active) 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) and Space Research Service (active) systems.

Earth Exploration-Satellite Service

The frequency range under consideration includes the co-primary EESS (active) allocation between 5250 and 5570 MHz that is used for satellite and airborne active remote sensing of surface deformation (e.g., volcanoes, earthquakes, and glacier movements) as well as the monitoring of agricultural crops, forest disturbances, and ocean vector winds. The frequency allocation for these applications in these bands is important because of the dimensional connection between the scattering mechanisms of the targets being observed.

Mobile services that include WAS/RLAN share this band from 5250-5350 MHz and 5470-5570 MHz. In addition, for selected countries in Region 3, there is also a fixed wireless access (FWA) allocation on a co-primary basis from 5250-5350 MHz that is governed by Recommendation ITU-R F.1613. There is no current mobile service allocation in the 120 MHz region extending from 5350-5470 MHz. Providing mobile access to this new band has the potential for increasing aggregate interference over large geographic regions. Satellite sensors that use this band are listed in Table 2.6. It is important to note that these sensors have a variety of applications and use different measurement principles (e.g., synthetic-aperture radar,

Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

TABLE 2.6 Satellite Sensors at 5300 to 5500 MHz

Sensor Center Frequency (MHz) Bandwidth (MHz)
Sentinel 1A 5405 100
Envisat (ASAR) 5331 16
RISAT-1 5350 18.75-75
Radarsat-2 5405 11.6, 17.3, 30, 50, and 100
Radarsat-3 (RCM) 5405 14-100
Radarsat Next Generation 5405 13-300
Jason-2/3 SSALT, POSEIDON-3/3B 5300 100, 320
Sentinel-3 5410 320
HY-2A 5250 160
Sentinel-6, POSEIDON-4 5410 320
MetOp-A, B, C (ASCAT) 5255, 5355 0.5, 2
MetOp-SG (SCA) 5355 2

NOTE: Acronyms are defined in Appendix B.

scatterometry, radar altimetry, etc.), so any planned compatibility studies must include a full range of cases.

Recommendation: The committee agrees with the resolution that compatibility studies are critical to ensure the protection of the Earth Exploration-Satellite Service (EESS) (active) in the 5350-5470 MHz band from unwanted emissions from planned radio local area networks (WAS/RLAN) units. Such studies should also assess the impact of ITU-R F.1613 on the data collected by current satellites. Future protection of the EESS (active) allocation could be achieved through coordination with published satellite ephemerides. However, no changes should be made to the Radio Regulations unless acceptable technical and operational restrictions can be specified to facilitate non-interference with existing or planned EESS active systems.

Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

WRC-23 AGENDA ITEM 2.2:
RADAR SOUNDERS AT 45 MHZ

WRC-23 Agenda Item 2.2 will “conduct, and complete in time for WRC-23, studies for a possible new allocation to the Earth exploration-satellite service (active) service for spaceborne radar sounders with the range of frequencies around 45 MHz, taking into account the protection of incumbent services, in accordance with Resolution 656 (WRC-15).”

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), and SKA prototype antennas in Australia. These facilities are part of a renaissance in low-frequency radio astronomy now under way, with a promise of new and important discoveries. A recent example in this frequency range includes a new natural phenomenon: intrinsic radio emission from fireballs (large meteors), recently discovered by the Long Wavelength Array. Astronomers around the world are now conducting follow-up observations. Also, careful measurements of the sky background temperature in this frequency range are important for calibration of sensitive cosmology measurements (e.g., cosmic dawn) at higher frequencies (100-200 MHz). The impact of the radar could be significant in view of the likely large footprint on the ground of transmissions from the satellite at these relatively low frequencies. Note that the individual dipole elements see the entire sky, and the individual elements have limited sidelobe rejection, placing difficult demands on the dynamic range of the signal-processing systems in the presence of strong interference anywhere in the sky. Further, the best times for operation of the radar, with stable ionospheric conditions, coincide with the best times for radio astronomical observations for the same reason.

Recommendation: The committee urges administrations to protect current and future radio astronomy facilities from harmful interference in the frequency range near and around 45 MHz. Coordination between the use of a satellite-based radar system and both passive and active radio astronomy and

Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×

remote sensing observations should be explored. The committee endorses the importance of the pending characterization of the new radar system in time for WRC-23.

Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 12
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 13
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 14
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 15
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 16
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 17
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 18
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 19
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 20
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 21
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 22
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 23
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 24
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 25
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 26
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 27
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 28
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 29
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 30
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 31
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 32
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 33
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 34
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 35
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 36
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 37
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 38
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 39
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 40
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 41
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 42
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 43
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 44
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 45
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 46
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 47
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 48
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 49
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 50
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 51
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 52
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 53
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 54
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 55
Suggested Citation:"2 Views of the U.S. National Academies of Sciences, Engineering, and Medicine on Selected WRC-19 and WRC-23 Agenda Items." National Academies of Sciences, Engineering, and Medicine. 2017. 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. Washington, DC: The National Academies Press. doi: 10.17226/24899.
×
Page 56
Next: Appendixes »
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 Get This Book
×
Buy Paperback | $55.00 Buy Ebook | $44.99
MyNAP members save 10% online.
Login or Register to save!
Download Free PDF

The radio frequency spectrum is a limited resource with ever increasing demand from an expansive range of applications—all the way from commercial, such as mobile phones, to scientific, such as hurricane monitoring from space. Since radio waves do not stop at national borders, international regulation is necessary to ensure effective use of the radio spectrum for all parties.

Every 2 to 5 years, the International Telecommunication Union convenes a World Radiocommunication Conference (WRC) to review and revise the international radio regulations. This report provides guidance to U.S. spectrum managers and policymakers as they prepare for the WRC in 2019. While the resulting document is targeted primarily at U.S. agencies dealing with radio spectrum issues, other Administrations and foreign scientific users may find its recommendations useful in their own WRC planning.

  1. ×

    Welcome to OpenBook!

    You're looking at OpenBook, NAP.edu's online reading room since 1999. Based on feedback from you, our users, we've made some improvements that make it easier than ever to read thousands of publications on our website.

    Do you want to take a quick tour of the OpenBook's features?

    No Thanks Take a Tour »
  2. ×

    Show this book's table of contents, where you can jump to any chapter by name.

    « Back Next »
  3. ×

    ...or use these buttons to go back to the previous chapter or skip to the next one.

    « Back Next »
  4. ×

    Jump up to the previous page or down to the next one. Also, you can type in a page number and press Enter to go directly to that page in the book.

    « Back Next »
  5. ×

    Switch between the Original Pages, where you can read the report as it appeared in print, and Text Pages for the web version, where you can highlight and search the text.

    « Back Next »
  6. ×

    To search the entire text of this book, type in your search term here and press Enter.

    « Back Next »
  7. ×

    Share a link to this book page on your preferred social network or via email.

    « Back Next »
  8. ×

    View our suggested citation for this chapter.

    « Back Next »
  9. ×

    Ready to take your reading offline? Click here to buy this book in print or download it as a free PDF, if available.

    « Back Next »
Stay Connected!