Views of the U.S. NAS and NAE on Agenda Items at the World Radiocommunication Conference 2015 (2013)

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Views on WRC-15 Agenda Items

The following pages discuss the committee’s consensus on the potential impact and relevance of certain agenda items at issue at the upcoming World Radiocommunication Conference (WRC) in 2015.

AGENDA ITEM 1.1: TERRESTRIAL MOBILE BROADBAND APPLICATIONS

Agenda Item 1.1 considers “additional spectrum allocations to the mobile service on a primary basis and identification of additional frequency bands for International Mobile Telecommunications (IMT) and related regulatory provisions, to facilitate the development of terrestrial mobile broadband applications, in accordance with Resolution 233 (WRC-12).”

This agenda item is asking administrations to study ways of making additional bandwidth available for IMT, preferably worldwide, and to make submissions to the International Telecommunications Union-Radiocommunication Sector (ITU-R) for consideration prior to WRC-15. It appears to be addressing the broad and generic frequency range from 400 MHz to 6 GHz; however, higher frequencies may also be under consideration. The committee urges administrations to consider the needs of Radio Astronomy Service (RAS) and Earth Exploration-Satellite Service (EESS) services, both passive and active, when making any new allocations to IMT. Care is required in deciding new allocations to prevent interference from in-band, out-of-band, and spurious emissions, given the technological limitations of mobile applications. Furthermore, the proposed application (broadband telecommunications) is often spread-spectrum in nature. As such, it may be problematic for passive (receive-only) applications since its signals may resemble thermal noise for EESS and RAS instruments, interfering with the types of signals detected. It is important to note that ITU footnote 5.340 says “all emissions are prohibited in the bands 1400-1427 MHz and 2690-2700 MHz”¹ among many other bands at frequencies above 6 GHz.

Radio Astronomy Service

Several bands in the subject frequency range are allocated on a primary basis to RAS, including 406-410 MHz, 1400-1427 MHz, 1610.6-1613.8 MHz, 2690-2700 MHz and 4990-5000 MHz. These bands are widely used in RAS applications and care must be taken not to interfere with established observatories using these frequencies. Several other bands are secondarily allocated to RAS and are also widely used and require protection (see listing in Table 2.1). The committee notes that several major RAS facilities operate in this frequency range, including the Robert C. Byrd Green Bank Telescope

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¹ Except those provided for by Footnote 5.422 in the case of 2690-2700 MHz.

TABLE 2.1 Current RAS and EESS (Active and Passive) Frequency Allocations in 400 MHz to 6 GHz

^a EESS (active) is secondary in this band in the international table and gains secondary status through Footnote US 397 in the U.S. table.

^b Per 5.149 and US 342.

^c Per 5.339.

^d Per 5.385.

^e Per 5.149 and US 342.

^f Per 5.438.

(GBT), the Karl G. Jansky Very Large Array (VLA), the Very Long Baseline Array (VLBA, an instrument with 10 discrete receiving stations spread over North America), and the Arecibo Observatory, for studies of galactic synchrotron continuum emission, neutral hydrogen (HI), pulsars, and active galactic nuclei.

Earth Exploration-Satellite Service

EESS passive applications will often use frequencies in bands protected for RAS passive use since the two services are completely compatible. In fact, EESS shares primary allocations with RAS at 1400-1427 MHz and 2690-2700 MHz and secondary allocations at 2655-2670 MHz. This practical solution results in multiple shared bands. Passive EESS users below 6 GHz include several satellite facilities, which deliver science and operational data for climate science and weather forecasting. These include the European Soil Moisture and Ocean Salinity (SMOS) mission, NASA’s Aquarius Mission, and the soon-to-be-launched Soil Moisture Active/Passive

(SMAP) mission, each providing a record of soil moisture and/or ocean salinity, with passive sensors operating in the band at 1400-1427 MHz.

In addition to the protected bands shared with RAS, EESS uses several active bands in the subject frequency range. The 1215-1300 MHz band is used for Earth surface characterization by the Aquarius and SMAP missions. The 5250-5570 MHz radar band has been extensively used for synthetic aperture radar (SAR) missions and experiments to characterize Earth’s surface. The active instruments are also subject to radiofrequency interference (RFI), and careful management is needed for successful science applications. Figure 2.1 is an example of the potential for problems with RFI when various uses are shared within a band. These data are from the radar scatterometer that is part of the Aquarius/SAC-D satellite. It operates at 1260 MHz and the primary application is over ocean (although future sensors such as that planned for SMAP will have a primary mission over land). The sensor helps correct for the effect of waves on the retrieval of sea surface salinity. Figure 2.1 provides the per-

FIGURE 2.1 The distribution of RFI in the active band as detected by the scatterometer (radar) aboard the Aquarius/SAC-D satellite. The map shows the percentage of radar observations contaminated by RFI. The radar operates in the band 1215-1300 MHz and the figure is an illustration of the potential for RFI problems in the active EESS services. SOURCE: David Le Vine, NASA Goddard Space Flight Center.

centage of samples corrupted by RFI, showing the impact of RFI on potential applications over land.

Recommendation: The committee urges administrations to consider the needs of the Radio Astronomy Service and the Earth Exploration-Satellite Service (both passive and active) when making any new allocations to International Mobile Telecommunications (IMT). The committee supports the shared use of the spectrum for this purpose but recommends that rigorous compatibility studies be carried out to determine how services may effectively share the spectrum before any such allocations are made to IMT.

AGENDA ITEM 1.3: BROADBAND PUBLIC PROTECTION AND DISASTER RELIEF

Agenda Item 1.3 is “to review and revise Resolution 646 (Rev. WRC-12) for broadband public protection and disaster relief (PPDR), in accordance with Resolution 648 (WRC-12).”

The committee expresses support for exploring the use of technologies to facilitate emergency response in the immediate aftermath of a catastrophic event and for public protection. The committee notes, however, that in evaluating frequency planning and minimizing the potential for harmful interference, consideration must be given to passive scientific use of the spectrum. Indeed, some passive and active scientific uses of the spectrum may help to predict and mitigate the effects of natural disasters. While deploying PPDR systems in the event of a disaster is not an issue and is indeed endorsed by the committee, the testing of such systems, as well as their use in less urgent situations, could adversely impact scientific services. In particular, it is noted that PPDR systems are often aerially deployed, which results in a strong potential for interference to radio astronomy facilities when such systems are being tested.

Radio Astronomy Service

The 380-470 MHz band mentioned in the resolution contains a primary allocation for radio astronomy at 406.1-410 MHz, which is an important band for interstellar medium studies, pulsars, and baryonic acoustic oscillations.

The mentioned band 4940-4990 MHz is adjacent to the RAS primary allocation at 4990-5000 MHz, which is an important allocation for very long baseline interferometry.

Recommendation: The committee supports studying radio systems for public protection and disaster relief to increase the efficiency and application of such systems. These studies should take into consideration the potential impact on spectrum use by passive services of testing and deploying PPDR systems.

AGENDA ITEM 1.6: ALLOCATION OF 250-300 MHZ IN THE 10-17 GHZ RANGE

Agenda Item 1.6 considers “possible additional primary allocations: to the fixed-satellite service (Earth-to-space and space-to-Earth) of 250 MHz in the range between 10 GHz and 17 GHz in Region 1 [Agenda Item 1.6.1]; and to the fixed-satellite service (Earth-to-space) of 250 MHz in Region 2 and 300 MHz in Region 3 within the range 13-17 GHz [Agenda Item 1.6.2].”

There are a number of existing allocations for scientific services in this frequency range, including passive use by RAS and both passive and active allocations to EESS. Passive use by EESS/RAS is compatible with all other passive users of the electromagnetic spectrum. When considering the impact of frequency allocations on other users, it is also important to note that certain scientific uses cannot be shifted to other frequencies due to the natural origin of the emission features.

Radio Astronomy Service

Primary considerations for RAS are unwanted out-of-band emission from fixed-satellite service (FSS) in neighboring bands. Spurious and out-of-band emission can potentially exist anywhere in the spectrum, and new allocations to FSS at these frequencies could be particularly deleterious to RAS because satellites are difficult to avoid: They appear at high elevations and therefore enter into the line-of-sight of radio telescopes conducting astronomical observations. Almost all major U.S. radio observatories have versatile receivers capable of observing within the specified frequency range. While RAS has limited allocations within this band, common practice is to observe throughout this range. These receivers are used to observe continuum emission from nonthermal synchrotron sources, which reveal the high-energy jets driven by black holes in the centers of galaxies and spinning dust within our own galaxy. Spectral line observations in this frequency range include the formaldehyde transition at 14.4885 GHz (rest frequency) and Doppler shifted carbon monoxide from distant galaxies.¹

Of significant concern for RAS would be modifications of the current allocations for FSS at 14.47-14.5 GHz, which are currently Earth-to-space. RAS has a secondary allocation at 14.47-14.5 GHz

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¹ The Doppler shift associated with the expansion of the universe is characterized by the parameter z (known as redshift), such that the observed frequency is lower than the emitted frequency by a factor of 1 + z.

(Footnote 5.149) associated with observations of the formaldehyde transition at 14.4885 GHz (rest frequency). If the FSS allocation is revised to include space-to-Earth at these frequencies in Region 1 (Agenda Item 1.6.1), radio observatories in Europe may be adversely impacted.

Earth Exploration-Satellite Service

The primary concern for EESS is out-of-band emissions interfering with reception in the allocated bands of 10.6-10.7 GHz (Footnote 5.149) and 15.35-15.40 GHz (Footnote 5.340). In addition, EESS (active) has an allocation at 13.25-13.75 GHz. Altimeters and scatterometers on satellite observatories such as Cryosat, Jason-2, Jason-3, Jason-CS, Sentinel-3, HY-2, WindSat, GCOM, and GMI use this band. Observations in both the passive and active bands are used for a number of applications including observations of soil moisture, sea surface temperatures, sea surface height, ocean winds, sea ice, snow, and precipitation. These observations are critically important to predict weather, monitor climate, quantify changes in global water cycle, monitor and predict agricultural productivity and to better understand linkages and feedback in ocean circulation and climate change.

The proposed modification to spectrum usage as given in the agenda item includes bands that are allocated to EESS (both passive and active). In addition, allocation of bands adjacent to these EESS bands may severely impact Earth remote sensing through out-of-band emissions. EESS sensors are particularly sensitive to out-of-band emission from space-to-Earth transmissions since the satellite-based transmitter is visible to virtually all EESS users. Even downward-looking sensors are sensitive to RFI from satellites due to reflections from the surface.

Recommendation: The committee recommends that any new fixed-satellite service (FSS) allocations strictly adhere to all current regulation requirements for unwanted emission and out-of-band emission in the protected scientific service bands.

AGENDA ITEM 1.9: POSSIBLE NEW ALLOCATIONS AT 7150-7250 MHZ, 8400-8500 MHZ, 7375-7750 MHZ, AND 8025-8400 MHZ

Agenda Item 1.9 considers “in accordance with Resolution 758 (WRC-12): possible new allocations to the fixed-satellite service in the frequency bands 7150-7250 MHz (space-to-Earth) and 8400-8500 MHz (Earth-to-space), subject to appropriate sharing conditions [Agenda Item 1.9.1]; and the possibility of allocating the bands 7375-7750 MHz and 8025-8400 MHz to the maritime-mobile satellite service and additional regulatory measures, depending on the results of appropriate studies [Agenda Item 1.9.2].”

The 7000-8500 MHz band includes primary allocations to Fixed Service (FS) and Mobile Service (MS). In addition, Space Research Service (SRS) has primary allocations to support deep space missions at 7145-7190 MHz and 8400-8450 MHz; SRS also has primary allocations at 7190-7235 MHz and 8450-8500 MHz to support near-Earth missions, Earth to space (E-s) and space to Earth (s-E), respectively. Furthermore, EESS has a primary allocation for s-E between 8025-8400 MHz. In the United States, subject to Footnote 5.461, Mobile-satellite Service (MSS) has been allocated 7250-7300 MHz (s-E) and 7900-8025 MHz (E-s) on a primary basis. Worldwide, 7250-7750 MHz and 7900-8400 MHz have been allocated to FSS on a primary basis, for downlink (s-E) and uplink (E-s), respectively.

Agenda Item 1.9.1 aims to add an additional 100 MHz above and below the current range for FSS. As listed above, both of these bands are currently allocated to FS, MS, and SRS.

Agenda Item 1.9.2 aims to extend the allocation of Maritime Mobile-Satellite Service (MMSS) to regions of the spectrum within the FSS allocation, specifically 7375-7750 MHz and 8025-8400 MHz.

Radio Astronomy Service

In the United States, the Very Large Array (VLA), the Very Long Baseline Array (VLBA), the Green Bank Telescope (GBT), and Arecibo Observatory all use the 7-9 GHz band for continuum studies of astrophysical objects ranging from planets to stars to galaxies. Radio spectroscopy and broad band continuum observations have identified and characterized the birth sites of stars in the galaxy, the processes by which stars slowly die, and the complex distribution and evolution of galaxies in the universe. The enormous energies contained in the enigmatic quasars and radio galaxies discovered by radio astronomers has led to the recognition that most galaxies, including our own Milky Way, contain a super massive black hole at

their center, a phenomenon that appears to be crucial to the creation and evolution of galaxies. Synchronized observations using widely spaced radio telescopes around the world give extraordinary angular resolution far superior to that which can be obtained using the largest optical telescopes on the ground or in space.

Agenda Item 1.9.1

The addition of new allocations 7150-7250 (s-E) and 8400-8500 MHz (E-s) to FSS would have some impact on VLA, GBT, and other radio observatories that currently make use of this band. Specifically, the current allocation of 8400-8500 MHz to SRS has allowed RAS to use this band, without formal protection, since there are relatively few deep space missions, and the signals they send back to Earth are very faint compared to typical satellite downlinks. New allocations to FSS at these frequencies would be particularly deleterious to RAS because satellites are difficult to avoid: They appear at high elevations, can cross much of the sky, and therefore enter into the line of sight of radio telescopes conducting astronomical observations. The committee notes that SRS receivers will experience similar adverse effects from satellites as well.

Agenda Item 1.9.2

New allocations for maritime-mobile satellite service from 7375-7750 MHz (s-E) and 8025-8400 MHz (E-s) are likely to have some impact on VLA and other radio telescopes using this band. However, the Earth-to-space uplinks are much less likely to affect radio telescopes since radio observatories are generally distant from shorelines (with two exceptions: the VLBA_SC antenna in Saint Croix and the VLBA_MK antenna in Hawaii).

Earth Exploration-Satellite Service

The 7-9 GHz band is currently used by meteorological satellites (MetSat) with applications to the measurements of Earth variables necessary for operational meteorology, forecasts, numerical weather prediction (NWP), climate monitoring, and climate change studies. Currently, 7450-7550 MHz is used for geostationary orbit (GSO) downlinks (s-E) and 8175-8215 MHz is used for uplinks (E-s) by MetSat. However, some EESS downlink Earth stations are located near the coast and therefore could suffer interference from new proposed maritime transmissions within 8025-8400 MHz near these

regions unless acceptable sharing criteria or exclusion zones are established.

Conclusion: The committee is not in favor of the proposed FSS allocations of 7150-7250 MHz (s-E) and 8400-8500 MHz (E-s) due to their potential conflicts with radio astronomy observations at these frequencies. The committee does not oppose the proposed Maritime Mobile-Satellite Service allocations 7375-7750 MHz (s-E) and 8025-8400 MHz (E-s) if ITU-R studies demonstrate compatibility with existing services.

AGENDA ITEM 1.10: MOBILE-SATELLITE SERVICE IN THE EARTH-TO-SPACE AND SPACE-TO-EARTH DIRECTIONS

Agenda Item 1.10 is “to consider spectrum requirements and possible additional spectrum allocations for the mobile-satellite service in the Earth-to-space and space-to-Earth directions, including the satellite component for broadband applications, including International Mobile Telecommunications (IMT), within the frequency range from 22 GHz to 26 GHz, in accordance with Resolution 234 (WRC-12).”

A principal concern is the 22.21-22.5 GHz band, which has a co-primary allocation between the EESS and RAS passive services and the fixed and mobile services, except for aeronautical and mobile services, and the 23.6-24 GHz band, which has primary allocation for EESS passive services. In the frequency range 22-26 GHz, there are primary allocations for RAS at 22.21-22.5 GHz and 23.6-24 GHz and footnote protection at 22.01-22.5 GHz, 22.81-22.86 GHz, and 23.07-23.12 GHz (Footnotes 5.149 and US 342). There are primary allocations for EESS at 22.21-22.5 GHz (passive), 23.6-24 GHz (passive), and 25.5-27 GHz, and a secondary allocation at 24.05-24.25 (active). In the 22.21-22.5 GHz band, ITU Radio Regulations Footnote 5.149 states that, “administrations are urged to take all practicable steps to protect the radio astronomy service from harmful interference. Emissions from spaceborne or airborne stations can be particularly serious sources of interference to the radio astronomy service.” The proximity of communication uplinks to the allocated 22.21-22.5 GHz band increases the risk that out-of-band emissions will interfere with EESS and RAS passive services. Furthermore, ITU Footnote 5.340 says “all emissions are prohibited” in the 23.6-24.0 GHz band.

Radio Astronomy Service

The RAS passive service in the primary and secondary allocation bands has several key molecular transitions, which are used to study the structure of dense interstellar clouds. Understanding molecular clouds is an important goal of galactic astronomy. All star formation in our galaxy proceeds from molecular clouds and understanding the role they play in how stars form is fundamental to fully understanding the life cycle of stars. The most important transitions for the study of molecular clouds in these bands are the NH₃ 1(1)-1(1) and 2(2)-2(2) lines at 23.7 GHz, the CH₃OH line at 24.9 GHz, and H₂O at 22.2 GHz. Other species are also present, but the ones specifically mentioned are key probes of the physical conditions in molecular cloud cores. Molecular clouds can be studied

both in the Milky Way Galaxy and in external galaxies, where the relevant molecular transitions will be shifted toward lower frequencies by the expansion of the universe.¹ In external galaxies, water maser emission at 22 GHz, particularly from 22.2 GHz down to the red-shifted frequency of 21.2 GHz, is extremely useful in determining distances to distant galaxies. Given that the determination of distances in astronomy is one of the most fundamental problems, the importance of observations at this frequency cannot be overstated.

Earth Exploration-Satellite Service

For EESS, the 23.6-24.0 GHz band is currently used extensively in operational environmental satellite systems to provide measurements of total integrated water vapor and cloud liquid water. These are key measurements for many current models of climate and environmental impact. Uses of this frequency include hurricane tracking, ocean topography, oil spill monitoring, and ship routing.

In addition, passive measurements from EESS satellites near the water vapor absorption line at 22.2 GHz are essential not only for measuring atmospheric water vapor but also for reducing error in other geophysical parameters due to the presence of water vapor, especially in moist atmospheres. For example, the accuracy in measuring sea surface wind speed, sea surface temperature, liquid cloud water or precipitation would significantly degrade if the 22 GHz water vapor channel was not present or was unusable due to RFI contamination.²

Recommendation: The committee recommends that any new Mobile-Satellite Service allocations strictly adhere to all current regulation requirements for unwanted emission and out-of-band emission in the protected scientific service bands, which includes a critical tracer of water vapor in the atmosphere.

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¹ The Doppler shift associated with the expansion of the universe is characterized by the parameter z (known as redshift), such that the observed frequency is lower than the emitted frequency by a factor of 1+ z.

² As found in National Research Council, Views of the NAS and NAE on Agenda Items at Issue at the World Radiocommunication Conference 2012, The National Academies Press, 2013, p. 26.

AGENDA ITEM 1.11: A PRIMARY ALLOCATION FOR THE EARTH EXPLORATION-SATELLITE SERVICE (EARTH-TO-SPACE ) IN THE 7-8 GHZ RANGE

Agenda Item 1.11 considers “a primary allocation for the Earth exploration-satellite service (Earth-to-space) in the 7-8 GHz range, in accordance with Resolution 650 (WRC-12).”

Radio Astronomy Service

The impact of this agenda item on RAS is expected to be minimal. Existing EESS Earth-to-space terminals are few in number relative to other services and are in fixed locations that have negligible impact on RAS. Furthermore, the potential impact on RAS of Earth-to-space communications is much less severe than space-to-Earth.

Earth Exploration-Satellite Service

Given that the associated terminals are few in number and are in fixed locations, the impact on EESS would be minimal.¹ Furthermore, this agenda item will have a positive impact on EESS scientific programs by supporting uplink operations.

Conclusion: Given the fact that the proposed frequency allocation will support Earth Exploration-Satellite Service (EESS) scientific programs with little deleterious impact on Radio Astronomy Service or EESS (passive), the committee supports Agenda Item 1.11.

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¹ However, it should be noted that the NASA Deep Space Network uses 7.145-7.190 GHz for communication with deep space missions (e.g., planetary and outer solar system science). These missions provide invaluable information on the nature of our solar system, so an allocation outside this band is preferred.

AGENDA ITEM 1.12: EXTENSION OF WORLDWIDE ALLOCATION TO EESS (ACTIVE ) TO 8700-9300 MHZ AND/OR 9900-10500 MHZ

Agenda Item 1.12 considers “an extension of the current worldwide allocation to the Earth exploration-satellite (active) service in the frequency band 9 300-9 900 MHz by up to 600 MHz within the frequency bands 8700-9300 MHz and/or 9900-10500 MHz, in accordance with Resolution 651 (WRC-12).”

Radio Astronomy Service

Observations with radio telescopes at these frequencies measure the continuum emission from astrophysical sources, such as quasars, which can reveal the physical processes dominating the energetic cores of many galaxies. Existing instrumentation on U.S. radio astronomy facilities includes receivers that are optimal within 8000-10000 MHz (X band). These receivers are compatible with all other passive users of the radio spectrum and with active users that are geographically shielded from the fixed locations of the radio observatories. Allocation of additional active services for EESS above 9300 MHz is unlikely to impact RAS significantly.

Earth Exploration-Satellite Service

The proposed extension of the 9300-9900 MHz band allocated for EESS active services will further enhance Earth remote sensing applications. However, allocation of the additional EESS (active) services in the band at 9900-10500 MHz is a concern for EESS passive services conducted in the protected 10600-10700 MHz band because of the potential for unwanted out-of-band emissions. ITU Footnote 5.340 says “All emissions are prohibited in the 10.68-10.7 GHz band except those provided for by No. 5.483.” This protected band is critical for measurement of parameters such as sea surface winds, soil moisture, and precipitation.

Recommendation: Additional allocations to Earth Exploration-Satellite Service active services should follow existing regulatory requirements and recommendations for demonstration studies (Resolution 651) to ensure that unwanted out-of-band emissions will not impact the passive scientific services in the neighboring 10600-10700 MHz band.

AGENDA ITEM 1.16: AUTOMATIC IDENTIFICATION SYSTEM TECHNOLOGY APPLICATIONS AND MARITIME RADIOCOMMUNICATION

Agenda Item 1.16 considers “regulatory provisions and spectrum allocations to enable possible new Automatic Identification System (AIS) technology applications and possible new applications to improve maritime radio communication in accordance with Resolution 360 (WRC-12).”

Radio Astronomy Service

Radio astronomy observations of the 21 cm hydrogen line red-shifted¹ to the 150.05-153 MHz band are used to study the Epoch of Reionization (EoR) in the early universe. RAS has primary status in this band in ITU Region 1. Current programs to study the EoR include observations with the Long Wavelength Array (LWA) in New Mexico, the Low Frequency Array (LOFAR) in Europe, the Murchison Widefield Array (MWA) in Western Australia, the Giant Metrewave Radio Telescope (GMRT) in India, and the Precision Array for Probing the Epoch of Reionization (PAPER) in South Africa. New frequency allocations should avoid regions of the spectrum allocated to the passive scientific services.

Recommendation: The committee recommends that any new Automatic Identification System (AIS) allocations avoid the bands allocated to the passive scientific services and strictly adhere to all current regulation requirements for unwanted emission and out-of-band emission in the protected scientific service bands. In particular, new channels assigned to enhance the AIS service should avoid the 150.05-153 MHz band, which is allocated on a primary basis in Region 1 to Radio Astronomy Service.

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¹ The Doppler shift associated with the expansion of the universe is characterized by the parameter z (known as “redshift”), such that the observed frequency is lower than the emitted frequency by a factor of 1 + z.

AGENDA ITEM 1.17: WIRELESS AVIONICS INTRA-COMMUNICATIONS

Agenda 1.17 considers “possible spectrum requirements and regulatory actions, including appropriate aeronautical allocations, to support wireless avionics intra-communications (WAIC), in accordance with Resolution 423 (WRC-12).”

This agenda item does not indicate the specific frequency range of interest, but the desired allocation would come from existing Aeronautical Mobile Service (AeMS), Aeronautical Mobile (R) Service (AM(R)S), and Aeronautical Radionavigation Service (AeRNS). Additional frequency bands above 15.7 GHz would be considered if the requirements cannot be met in the existing aeronautical allocations.

In this context, current allocations of concern for the scientific services below 15.7 GHz are 117.975-137 MHz MetSat under Radio Regulation No. 5.203; 5350-5460 MHz EESS (active); and 13.25-13.4 GHz EESS (active) and Space Research Service (active) (SRS). In addition, if radio navigation bands are considered for WAIC, this could affect usage of 74.8-75.2 MHz, which is in close proximity to the 73-74.6 MHz allocation to RAS, and of 15.4-15.43 GHz, which is adjacent to the 15.35-15.4 GHz RAS allocation.¹

Radio Astronomy Service

In common practice, radio observatories operate in all of these bands. The 117.975-137 MHz and 73-74.6 MHz bands are of particular interest to EoR studies because they encompass the 21 cm line at redshifts from 11 to 9 which are very close to the predicted trough and peak in the spectrum of the EoR of the early universe.² Aircraft travel at high elevations, so they can enter into the line of sight of radio telescopes, with very adverse impact.

Earth Exploration-Satellite Service

Space-borne active sensors have been used to study Earth’s surface and atmosphere using sensors such as synthetic aperture radars (SAR), altimeters, scatterometers, and precipitation and

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¹ ITU Footnote 5.340 says, “All emissions are prohibited in 15.35-15.4 GHz, except those provided for by No. 5.511.”

² The Doppler shift associated with the expansion of the universe is characterized by the parameter z (known as redshift), such that the observed frequency is lower than the emitted frequency by a factor of 1 + z.

cloud radars. These sensors provide multiple geophysical parameters used for weather forecasting and climate monitoring, including the altitude of Earth’s ocean surface, ocean surface wind speed and direction, cloud water amount, and precipitation rate. Examples of EESS active sensors are RADARSAT-2, Jason-1 and Jason-2, Jason-3 (upcoming), QuikSCAT/SeaWinds, the Tropical Rainfall Measuring Mission (TRMM), and OceanSat-2/OSCAT. As an example of frequency selection, the TOPEX/Poseidon follow-on missions Jason-1 and Jason-2 use a dual-frequency radar altimeter that measures in the K_u (13.575 GHz) and C (5.3 GHz) bands. The choice of frequency depends on the Earth/ocean surface interaction with the electromagnetic field and therefore cannot be chosen arbitrarily. Dual frequency operation allows ionospheric delay compensation for adequate accuracy of measurements. The bandwidth is selected according to necessary accuracy and resolution of the measurements and can vary from 300 kHz to 300 MHz.

Interference from direct path signals and signals reflected off Earth’s surface can affect measurements made by EESS sensors over large areas. The higher the originating transmitter, the larger the area affected. The airborne application is global and when combined with the emitter altitude, it becomes impossible to achieve geographic isolation of the signals.

Recommendation: No new allocations to wireless avionics intra-communications (WAIC) should be made unless acceptable criteria are developed to avoid interference with Radio Astronomy Service (RAS) and Earth Exploration-Satellite Service (both active and passive). Particular care should be taken to limit out-of-band emissions if WAIC allocations are made in the 74.8-75.2 MHz band (in close proximity to the 73-74.6 MHz RAS allocation) or the 15.4-15.43 GHz band (adjacent to the 15.35-15.4 GHz RAS allocation).

AGENDA ITEM 1.18: PRIMARY ALLOCATION TO THE RADIOLOCATION SERVICE FOR AUTOMOTIVE APPLICATIONS IN THE 77.5-78.0 GHZ BAND

Agenda Item 1.18 considers “a primary allocation to the radiolocation service for automotive applications in the 77.5-78.0 GHz frequency band in accordance with Resolution 654 (WRC-12).”

Industry is seeking to include 77.5-78 GHz, which is currently allocated to Amateur, Amateur-Satellite, Radio Astronomy and Space Research (space-to-Earth), in a wider band, 77-81 GHz, for Short Range Radar (SRR) for automobiles. This wider frequency band in which Radio Astronomy has primary allocations¹ contains several molecular spectral lines, including that of semi-heavy water (HDO), methanol (CH₃OH), and the ion N₂D⁺, that are very important to studies of the interstellar medium. These spectral lines provide unique information about star formation, including the formation of planets in other solar systems, the building blocks of biological molecules, the physics and chemistry of the interstellar medium, and the history of the early universe.

Radio Astronomy Service

The primary concern for radio astronomy is the operation of radars close to millimeter-wave radio observatories. Based on tests of a SRR conducted at the University of Arizona’s 12 meter mm-wave telescope located at Kitt Peak, Arizona, an exclusion zone in the ~30-40 km range around a mm-wave observatory would be required to keep interference from a single vehicle below the Recommendation ITU-R RA.769-2 level of-148 dBW/m²/MHz.² While smaller radii might suffice in areas without direct line of sight to the radio telescope, aggregate effects should be taken into account as more vehicles are outfitted with SRR in the coming years. ITU-R RA.1272-1 specifically recommends that such zones be established

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¹ In 77-81 GHz, RAS has primary allocations at 76.0-77.5 GHz (ITU and U.S tables); 78-79 GHz (U.S. table); and 79-81 GHz (ITU and U.S tables). In this range RAS has secondary allocations at 77.5-78 GHz (ITU and U.S tables) and 78-79 GHz (ITU table).

² National Radio Astronomy Observatory, “Measurements of Automotive Radar Emissions Received by a Radio Astronomy Observatory,” Electronics Division Technical Note No. 219, December 8, 2011.

around mm-wave astronomical observatories, following the procedure outlined in Recommendation ITU-R RA.1031-2.³

The committee is concerned about the further erosion of this important RAS band to accommodate automotive radar but appreciates the safety aspect of SRR. Compatibility studies would help ascertain whether provisions could be made to protect radio astronomy observatories and other sensitive facilities from emissions from the SRRs. The committee feels strongly that, at a minimum, the driver of a vehicle should be allowed to take personal responsibility for turning off the radar, with appropriate warnings to ensure safety, within an exclusion zone around a mm-wave observatory in the same manner as a switch allows vehicle headlights to be turned off when approaching an optical observatory at night. Alternatively, the radar could be automatically disabled by a geolocation device.

Recommendation: Comprehensive compatibility studies should be undertaken prior to allocating spectrum to the radiolocation service for automotive applications to ensure that provisions can be made to protect radio astronomy observatories and other sensitive facilities. Furthermore, the driver should be able to turn off the radar, with appropriate warning to ensure safety, within an exclusion zone around a millimeter-wave observatory. Alternatively, a geolocation device in the vehicle could automatically disable the radar and alert the driver of this action. Such protections should be applied to the whole 77-81 GHz band.

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³ Ibid. In addition it is noted that the automobile radars in close proximity to an optical telescope can interfere with sensitive charge coupled device (CCD) detectors. Automobiles within 20 m of an optical telescope could also exceed the limit of 2 ìW/m² in Recommendation 3 of the International Astronomical Union (IAU) Commission 50 (Appendix 4.1, Section 6.3, published in 1978) required to avoid radiofrequency power interfering with sensitive CCD detectors.

AGENDA ITEM 2: UPDATING THE REFERENCES IN THE RADIO REGULATIONS IN ACCORDANCE WITH PRINCIPLES CONTAINED IN THE ANNE X 1 TO RESOLUTION 27 (REV . WRC-12)

Agenda Item 2 reads as follows: “to examine the revised ITU-R Recommendations incorporated by reference in the Radio Regulations communicated by the Radiocommunication Assembly, in accordance with Resolution 28 (Rev.WRC-03), and to decide whether or not to update the corresponding references in the Radio Regulations, in accordance with the principles contained in Annex 1 to Resolution 27 (Rev.WRC-12).”

To clarify which Recommendations are incorporated into the Radio Regulations, a list of Recommendations incorporated by reference is published in the Radio Regulations. Recommendation ITU-R RA.769, which includes interference levels as a function of radio telescope parameters, has been in effect since the early 1970s, and until recently ITU-R RA.769-1 was referenced in the Radio Regulations. The updated Recommendation ITU-R RA.769-2 has been dropped from the list, which diminishes the ability of groups to draft and implement recommendations and regulations based on this important Recommendation. Similarly, RS.2017 provides important information on interference levels for EESS passive and should also be included.

Recommendation: The committee recommends that ITU-R RA.769-2 and RS.2017 be added to the list of recommendations incorporated by reference.