2

Views of the U.S. NAS and NAE on WRC-12 Agenda Items

The following pages provide a discussion of the committee’s consensus opinion on the potential impact and relevance of certain agenda items at issue at the upcoming World Radiocommunication Conference (WRC) in 2012.



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2 Views of the U.S. NAS and NAE on WRC-12 Agenda Items The following pages provide a discussion of the committee’s consensus opinion on the potential impact and relevance of certain agenda items at issue at the upcoming World Radiocommunication Conference (WRC) in 2012. 8

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AGENDA ITEM 1.3: SAFE OPERATION OF UNMANNED AIRCRAFT To consider spectrum requirements and possible regulatory actions, including allocations, in order to support the safe operation of unmanned aircraft systems (UAS), based on the results of ITU-R studies, in accordance with Resolution 421 (WRC 07). The relevant band is 5030-5150 MHz Aeronautical Radionavigation Service (ARNS) (microwave landing systems). The primary concern for radio astronomy is the potential for out-of-band emission from transmitters in the 5030-5150 MHz band causing interference in the primary RAS allocation 4990-5000 MHz and the secondary Radio Astronomy Service (RAS) allocation 4800-4990 MHz. Nearly all centimeter-wavelength radio telescopes operate in the 4800-5000 MHz band to study the continuum radio emission from stars, galaxies, quasars, gamma-ray bursts, and other sources of galactic and extragalactic thermal and nonthermal continuum radiation. Aircraft pose a special problem for ground-based radio astronomy facilities because there is a line-of-sight path out to hundreds of kilometers. A one-watt equivalent isotropically radiated power (EIRP) transmitter located 25 km (line of sight) from a radio astronomy facility needs to have its total out-of-band emissions in the RAS band under –72 dBc to conform to the continuum level specified in Recommendation ITU-R RA.769—that is, an average power density of less than –171 dBW/m2 in 10 MHz. It must also limit narrow band spurs to peaks no more than 11 dB above this average level in any 50 kHz channel within the RAS band, in order to conform to the corresponding spectral line level of –230 dBW/m2/Hz specified in Recommendation ITU-R RA.769. Recommendation: Transmissions in support of unmanned aircraft in the 5030-5150 MHz band should have sufficiently low level of unwanted emissions to avoid interference in the adjacent Radio Astronomy Service bands, in accord with Recommendation ITU-R RA.769. 9

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AGENDA ITEM 1.4: UNWANTED EMISSIONS INTO 4990-5000 MHZ To consider, based on the results of ITU R studies, any further regulatory measures to facilitate introduction of new aeronautical mobile (R) service (AM(R)S) systems in the bands 112-117.975 MHz, 960-1 164 MHz and 5 000-5 030 MHz in accordance with Resolutions 413 (Rev.WRC 07), 417 (WRC 07) and 420 (WRC 07). The primary concern for radio astronomy is the potential for out-of-band emission from transmitters providing surface applications at airports in the 5000-5030 MHz band that would cause interference in the primary RAS allocation, 4990-5000 MHz, and the secondary RAS allocation, 4800- 4990 MHz. Nearly all centimeter-wavelength radio telescopes operate in the 4800-5000 MHz band to study the continuum radio emission from stars, galaxies, quasars, gamma-ray bursts, and other sources of galactic and extragalactic thermal and nonthermal continuum radiation. A one-watt EIRP transmitter located 25 km (line of sight) from a radio astronomy facility needs to have its combined excess path loss and out-of-band emissions under −72 dBc to conform to the level specified in Recommendation ITU-R RA.769 that is, of a power density of less than −171 dBW/m2 for continuum observations in the 5 GHz RAS band. The corresponding value in Recommendation ITU-R RA.769 for spectral-line observations is a spectral power density of less than −230 dBW/m2/Hz, so that if the one watt transmitter has a bandwidth of 10 kHz the combined excess path loss and out-of-band emissions need to be less than −91 dBc. Recommendation: Transmitters providing surface applications at airports in the 5000-5030 MHz band should have sufficient suppression of out-of-band emissions to avoid interference in the adjacent 5 GHz Radio Astronomy Service band in accord with Recommendation ITU-R RA.769. 10

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AGENDA ITEM 1.6: 275-3000 GHZ To review No. 5.565 of the Radio Regulations in order to update the spectrum use by the passive services between 275 GHz and 3 000 GHz, in accordance with Resolution 950 (Rev.WRC 07), and to consider possible procedures for free-space optical-links, taking into account the results of ITU R studies, in accordance with Resolution 955 (WRC 07). The current Table of Frequency Allocations does not allocate bands above 275 GHz. Footnote No. 5.565 provides for the use of these bands up to 1000 GHz for all services and includes provisions meant to protect passive services until, and if, such time as the table is extended. Protection of the bands 275-1000 GHz for passive use is considered to be highly desirable; there is less emphasis on the range 1000-3000 GHz. Specific bands requiring protection are listed below in Tables 2.1 and 2.2. Recommendation: Administrations should protect the bands given in Tables 2.1 and 2.2 from harmful interference so they may be used by the Radio Astronomy Service and Earth Exploration-Satellite Service, respectively. Radio Astronomy Service Due to recent technological achievements, the exploration of the universe using the spectrum between 275 and 3000 GHz has greatly expanded over the past decade. Extraordinary opportunities exist to study the universe using this band, including those of the early universe, astrochemistry, planetary and star formation, and supermassive black holes. 1 The current and future activities in the 275-1000 GHz regions are substantial, as evidenced by the work of instruments such as the James Clark Maxwell Telescope (JCMT), the Caltech Submillimeter Observatory (CSO), the Submillimeter Telescope (SMT) of the Arizona Radio Observatory, the Submillimeter Array (SMA) and the South Pole Telescope (SPT), and the ongoing construction of the Atacama Large Millimeter/submillimeter Array (ALMA). The 275- 3000 GHz band also contains regions that are currently used for passive measurements for NASA missions (mainly in the 1-3 THz band) such as the Herschel Space Observatory and the Stratospheric Observatory for Far-Infrared Astronomy (SOFIA) and the future space project, the Single Aperture Far- Infrared Observatory (SAFIR). Because of high atmospheric absorption of signals due to water vapor above 1 THz, ground-based observations can only be made from extremely high sites, usually above 3 km. Exploratory observations have been made in this band, primarily around 1.5 THz. Because of the high horizontal opacity, interference from active services located more than 10 km away is unlikely. In light of these developments it is worthwhile to reexamine Footnote 5.565 in the Table of Frequency Allocations. The 275-3000 GHz region, known as “submillimeter,” encompasses various spectral windows that can be used for ground-based astronomy. These are illustrated in Table 2.1. It is a prime region for spectroscopy and for studying continuum emission from dust. 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 2.1). 2 These spectral lines are important probes of the interstellar medium where stars form because they trace relatively hot (T > 200 K) and dense (n > 107 cm-3) gas. These transitions also trace circumstellar gas close to the stellar photosphere and can be used to elucidate the physical processes including mass loss and photospheric shocks associated with evolved (i.e., giant) stars. This 1 NRC, Spectrum Management for Science in the 21st Century, The National Academies Press, Washington, D.C., 2010. 2 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. 11

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TABLE 2.1 Some Important Spectral Lines Between 275 and 3000 GHz Spectral Line Transition Frequency (GHz) Significance CO 3-2 345 Important tracer of galactic and 4-3 461 extragalactic structure 5-4 576 Probe of star-forming regions and 6-5 691 protoplanetary disks 7-6 807 8-7 922 Etc.a CI Fine structure 492 Tracer of the ionized dense 809 interstellar medium, photon- dominated regions, planetary nebulae HCO+ 4-3 356 Probe of high density regions, 5-4 446 protostellar cores 6-5 535 7-6 624 HCN 4-3 354 Probe of high density regions, 5-4 443 protostellar cores, 6-5 531 Inner shells of evolved stars 7-6 620 8-7 709 CS 7-6 342 Dense protostellar cores, evolved 8-7 392 stars, planetary nebulae 9-8 440 H 2O 1(1,0)-1(0,1) 556 Indicator of star formation, tracer for 2(1,1)-2(0,2) 752 life, maser emission 1(1,1)-0(0,0) 1113b H 3O + 0(0,0)-1(0,1) 984 Important tracer of ion-molecule 1(1,0)-1(1,1) 1655 chemistry 2(0,0)-1(0,1) 2972 H 2D + 1(1,0)-1(1,1) 372 Probe of D/H isotope ratio, chemical 3(2,1)-3(2,2) 646 fractionation CH 1-0 537 Important chemical building block, 2-1 1477 tracer of diffuse gas OH 1-0 2560 Star formation, O-rich evolved stars Metal hydrides 1-0 Various Interstellar coolants (SiH, LiH, MgH, 2-1 Building blocks of interstellar NaH, AlH) 3-2 chemistry Etc. a Higher excitation lines occur throughout this band at intervals of 115.27 GHz, e.g., 922 GHz and 1037 GHz. Higher frequency transitions are excited by regions of increasingly high temperatures. b The atmosphere is highly opaque at these frequencies and protection would only be needed for measurements above the atmosphere where satellite interference is possible. NOTE: To observe the listed transitions, fractional bandwidths of 1% are required for Galactic observations. 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 ten percent bandwidth is required to cover the nearby clusters of galaxies of which our galaxy is a member. 12

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TABLE 2.2 Representative Passive Sensing Bands and Their Associated Measurements in 275-1000 GHz Total Bandwidth Existing or Frequency Required Planned (GHz) (MHz) Spectral Line(s) (GHz) Measurement (GHz) 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 Wing channel for MASTER (HNO3), 300.22 (HOCl), temperature sounding 301.44 (N2O), 303.57 (O3), Window (296-306) for N2O, 305.2 (HNO3), 304.5 (O17O) O3 , O17O, HNO3, HOCl 313.5-355.6 42 100 {318.8, 345.8, 344.5} Water vapor sounding, cloud PREMIER, (HNO3), 313.8 (HDO), ice, wing channel for CIWSIR, {321.15, 325.15} (H2O), {321, temperature sounding MASTER, MWI, 345.5, 352.3, 352.6, 352.8} Window (339.5-348.5) for GOMAS, GEM (O3), {322.8, 343.4} (HOCl), H2O, CH3Cl, HDO, ClO, O3 345.8 (CO), {345.0, 345.4} HNO3, HOCl, CO, O18O, (CH3Cl), 345.0 (O18O), 354.5 HCN, CH3CN, N2O, BrO (HCN), 349.4 (CH3CN), {315.8, 346.9, 344.5, 352.9} (ClO), 351.67 (N2O), 346 (BrO) 361-365 4 000 364.32 (O3) Wing channel for water GOMAS vapor sounding for O3 369.2-391.2 22 000 380.2 (H2O) Water vapor sounding GEM, GOMAS 397-399 2 000 Water vapor sounding GOMAS 409-411 2 000 Temperature sounding 416-433.46 17 460 424.7 (O2) Temperature sounding GEM, GOMAS 439.1-466.3 27 200 {443.1, 448} (H2O), 443.2 Water vapor profiling, cloud MWI, CIWSIR (O3), 442 (HNO3) ice Window (458.5-466.3) for O3, HNO3, N2O, CO 477.75-496.75 19 000 487.25 (O2) Temperature sounding Odin 18 497-502 5 000 497.9 (N2 O), {497.6, 497.9} Wing channel for water SOPRANO, (BrO), 498.6 (O3) vapor sounding Window MASTER, Odin (498-502) for O3, CH3Cl, N218O, BrO, ClO 523-527 4 000 Window for 556.9 Wing channel for water vapor sounding Window (523-527) 538-581 43 000 {541.26, 542.35, 550.90, Water vapor sounding Odin 556.98} (HNO3), 556.93 Window (538-542) for (H2O), {544.99, 566.29, HNO3, O3, ClO 571.0} (O3), 575.4 (ClO) continues 13

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TABLE 2.2 Continued Total Bandwidth Existing or Frequency Required Planned (GHz) (MHz) Spectral Line(s) (GHz) Measurement (GHz) Instrument(s) 611.7-629.7 18 000 620.7 (H2O), 624.27 (ClO2), Water vapor sounding for MLS, SMILES, {624.34, 624.89, 625.84, ClO2, SO2, BrO, O3, H35Cl, SOPRANO 626.17} (SO2), {624.48, CH3Cl, O18O, HOCl, HO2, 624.78} (HNO3), 624.77 HNO3, CH3CN, H2O2 (81BrO), 624.8 (CH3CN), 625.04 (H2O2), 625.37 (O3), 624.98 (H37Cl), 625.92 (H35Cl), 627.18 (CH3Cl), 627.77 (O18O), {625.07, 628.46} (HOCl), 625.66 (HO2) 634-654 20 000 635.87 (HOCl), 647.1 (H218O), Wing channel for water MLS, SMILES 649.45 (ClO), 649.24 (SO2), vapor sounding Window 649.7 (HO2), 650.18 (81BrO), (634.8-651) for H218O, 650.28 (HNO3), 650.73 (O3), HOCl, ClO, HO2, BrO, 651.77 (NO), 652.83 (N2O) HNO3, O3, NO, N2O, SO2 656.9-692 35 100 658 (H2O), 660.49 (HO2), Water vapor sounding, cloud CIWSIR, MWI, 688.5 (CH3Cl), 691.47 (CO), ice Window (676.5-689.5) MLS 687.7 (ClO) for HO2, ClO, CO, CH3Cl 713.4-717.4 4 000 715.4 (O2) O2 18 729-733 4 000 731 (HNO3), 731.18 (O O) O18O, HNO3 750-754 4 000 752 (H2O) Water vapor 771.8-775.8 4 000 773.8 (O2) O2 823.15-845.15 22 000 834.15 (O2) O2 850-854 4 000 852 (NO) NO 857.9-861.9 4 000 859.9 (H2O) Water vapor 866-882 16 000 Cloud ice CIWSIR 905.17-927.17 22 000 916.17 (H2O) Water vapor 18 951-956 5 000 952 (NO), 955 (O O) O18O, NO SOPRANO 968.31-972.31 4 000 970.3 (H2O) Water vapor 985.9-989.9 4 000 987.9 (H2O) Water vapor NOTE: The atmosphere is highly opaque above 1000 GHz, and protection would only be needed for measurements where satellite interference is possible. SOURCE: Adapted from ITU, Working Party 7C, “Preliminary Draft New Report, ITU-R RS.[Above 275] Passive bands of Interest to EESS/SRS from 275 to 3000 GHz: Annex 1313 to Working Party 7C Chairman’s Report,” September 30, 2009. region also contains the two fine-structure lines of neutral carbon (CI). The CI lines are used to study photon-dominated regions, planetary nebulae, and HII regions. This range is also of great significance for the investigation of protoplanetary disks and their role in the origin of solar systems and life. In addition, the 275-3000 GHz region is the only spectral band containing the fundamental transitions of simple hydride species, such as CH, OH, SiH, LiH, and SH. This is because the moments of inertia of these 14

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molecules are quite small, resulting in large rotational energy splittings. Hydride molecules are extremely important for astronomy for several reasons. First, the large energy difference between the rotational levels makes them efficient coolants in dense gas. Also, because hydrogen is the most abundant element, hydride compounds are common in diffuse and dense clouds. Moreover, hydride species are the basic building blocks of interstellar chemistry. Understanding their abundances and distribution is key to chemical modeling. But not all hydride species are known interstellar molecules primarily because their exact transition frequencies have not yet been measured. Future research in this largely unexplored spectral region is likely to yield additional spectral transitions and continuum bands of interest to the passive services. Administrations are urged to protect the passive services from harmful interference, particularly those bands to be used by ALMA (275-375 GHz, 385-500 GHz, 602-720 GHz, and 787-950 GHz). Table 2.1 lists some important submillimeter molecular tracers, their frequencies, and their significance for astronomy. Earth Exploration-Satellite Service EESS (passive) currently uses spectrum in the range between 275 and 3000 GHz for several important measurements focusing on improving our understanding of the atmosphere and providing information needed by policy makers. A list of a few of these uses is given in Table 2.3. Table 2.2 gives a corresponding list of representative bands associated with these measurements. The list in Table 2.2 is not exhaustive. As in the case of radio astronomy, these measurements cannot be made in other bands because pressure-broadened transitions of different atmospheric constituents are being observed. In light of this and recent advances in relevant technologies, EESS use of this portion of the spectrum is expected to increase significantly. It is therefore important to protect EESS use in this region of the spectrum. TABLE 2.3 Typical EESS Uses of Spectrum from 275 to 3000 GHz Use/Measurement/Target Significance Mapping of ozone, polar Three-dimensional (3D) mapping of ozone in the stratosphere to stratospheric clouds, chlorine understand current ozone distribution and mechanisms for its sources depletion Cloud ice and frozen precipitation Key variable in the understanding of the water cycle, Earth’s energy budget, and the effect of cloud feedback on the climate, viewed in window regions around absorption features from gaseous constituents Upper troposphere and stratospheric Key aspect of the water cycle and important for determining climate water vapor feedback effects on radiative forcing in the presence of increasing greenhouse gases. Because multiple bands are used with varying sensitivity to water vapor, this use has varying applicability as a function of instrument scan type (nadir vs. limb) and water vapor distribution Stratospheric temperature Three-dimensional (3D) mapping of stratospheric temperature for understanding atmospheric dynamics Upper tropospheric pollution Understanding of distribution and transport of pollutants in the upper troposphere Trace gases Three-dimensional (3D) mapping of key atmospheric constituents (e.g., CO, SO2, HCl, BrO, N2O) tied to carbon cycle, global climate, pollution, and atmospheric transport NOTE: This list presents some significant uses of the spectrum but is not exhaustive. 15

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AGENDA ITEM 1.7: 1660 MHZ To consider the results of ITU R studies in accordance with Resolution 222 (Rev.WRC 07) in order to ensure long-term spectrum availability and access to spectrum necessary to meet requirements for the aeronautical mobile-satellite (R) service, and to take appropriate action on this subject, while retaining unchanged the generic allocation to the mobile-satellite service in the bands 1,525-1,559 MHz and 1,626.5-1,660.5 MHz. The primary concern for Radio Astronomy is the passive band from 1660 to 1670 MHz, which is shared with other services and is used to investigate phenomena associated with the formation of stars marked by maser emission from the hydroxyl radical (OH) in the stars’ atmosphere. Signals from OH “megamasers” seen in some galaxies are also observed in this band and provide information on the magnetic fields in these galaxies as well as their evolution over cosmic time. Recommendation: Aeronautical mobile-satellite (R) service transmissions in the overlapping and adjacent bands should have out-of band emissions below −237 dBW/(m2Hz) at registered Radio Astronomy Service sites, in accordance with Recommendation ITU-R RA.769 for spectroscopic observations. 16

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AGENDA ITEM 1.8: 71-238 GHZ Agenda Item 1.8 is the consideration of the progress of ITU R studies concerning the technical and regulatory issues relative to the fixed service in the bands between 71 GHz and 238 GHz, taking into account Resolutions 731 (WRC 2000) and 732 (WRC 2000). The millimeter wave spectrum above 70 GHz has become the subject of increasing interest for fixed wireless services due to its propagation characteristics and the wide bandwidth available for carrying communications traffic. New technology is now emerging that offers the possibility of using these higher bands for fixed wireless applications. Therefore, it is important the use of this frequency range for passive scientific observation be recognized. Recommendation: Administrations are urged to protect the passive services from harmful interference in 71-238 GHz. Per Tables 2.4 and 2.5, this band is extremely important for a wide range of scientific problems, both for Radio Astronomy Service and Earth Exploration-Satellite Service. Radio Astronomy Service This spectral region, which contains the 3 mm, 2 mm, and a large section of the 1.2 mm atmospheric windows, is extremely important for studies of virtually every aspect of the dense interstellar medium. 1 In fact, almost any given interstellar molecule has favorable transitions in this frequency band. Thus, this region is rich in spectral lines and high spectral resolution can be achieved, as shown in Figure 2.1. Millimeter molecular lines in the 71-238 GHz bands serve as important probes of dense gas in a wide variety of astronomical settings. High resolution spectroscopy and the Doppler effect allow the velocity structure of an astronomical source to be readily discerned through spectral line measurements. Millimeter transitions of molecules such as CO and H2CO have been used to trace galactic structure and the distribution of dense gas in our Galaxy and in external galaxies. Because stars form in dense molecular clouds, molecular lines in these bands are very useful probes of star formation, and have been used to locate young protostars and protostellar disks. Molecules are also common constituents of dying (or evolved) stars, and are present in large quantities in stellar ejecta of red giant and asymptotic giant branch stars. Molecular spectra have been successfully used to study the mass loss mechanisms from such stars and how they develop into white dwarfs and planetary nebulae. The low energy transitions of many molecules have also been used to examine the structure and chemical composition of diffuse clouds and cold, dense globules. Because multiple transitions of a given molecule can be observed in many of these objects, radiative transfer modeling can be done to accurately determine gas temperatures and densities, important physical quantities. Gaseous vapors emitted by comets are also investigated by observations of spectral lines at these wavelengths, and the climatology of planetary atmospheres in our solar system as well. Isotope ratios are also successfully probed in a wide variety of environments using mm molecular lines, such as 13CO and 12CO, HC14N and HC15N, and even Na35Cl and Na37Cl. Such ratios 1 This frequency range takes on this prominence because of fundamental quantum mechanics, and the nature of the dense interstellar medium. Dense interstellar gas (n ~ 103 to 107 cm-3) is typically cold, with temperatures in the range T ~ 10-100 K. Under such conditions, atomic energy levels are not populated, and only the very lowest energy levels of molecules can be accessed, namely, the rotational levels, as opposed to vibrational or electronic. Rotational energies of any given molecule are proportional to 1/ I, where I is the moment of inertia. Most simple molecules containing the cosmically-abundant elements H, C, N, O, and S have moments of inertia that place their rotational spectra in the 1-3 mm region (about 71-300 GHz). For example, the fundamental rotational transitions (i.e., J = 1 → 0) of the most abundant interstellar molecules, including CO (115 GHz), HCN (88 GHz), HCO+ (89 GHz), N2H+ (93 GHz), CN (113 GHz), NO (150 GHz), H2CO (72 GHz) and H2S (169 GHz) occur in these bands. The 71-238 GHz band also contains the next higher transitions (2 → 1, 3→ 2) of many of these molecules, as well. 17

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1.4 37 Indentified Features CH 3CHO 35 Unidentified Features ~6 lines per 100 km/s CH 3CHO + C2H5CN (CH 3)2O TRMS = 0.003 K (theoretical) HCOOCH 3 HCOOCH 3 1.2 C 2H3CN C 2H3CN HCOOCH 3 HCOOCH 3 + C2H3CN C 2H5CN C 2H5OH + (CH2OH)2 CH 3CHO + C2H3CN C 2H3CN + C2H5CN 1.0 CH 3CHO C 2H3CN HCOOCH 3 CH 3NH2 C 2H5CN C 2H3CN C 2H5CN HCOOCH 3 0.8 T R (K) C 2H5OH C 2H3CN * C 2H3CN HCOOH CH 3CHO C 2H5CN 0.6 NH2CHO C 2H5OH (CH 3)2O C 2H5OH U HNCO CH 3CHO 0.4 U U U U U U U U 0.2 CS OCS 13 0.0 231000 231200 231400 231600 231800 232000 Frequency (MHz) FIGURE 2.1 Typical spectrum of a dense molecular cloud, Sgr B2(N), obtained in a portion of the 71- 238 GHz band, using the Sub-Millimeter Telescope (SMT) of the Arizona Radio Observatory using a single-sideband (SSB) receiver covering a 1 GHz band. Integration time is 2 hours. A large fraction, but not all, of the molecular lines have been labeled on the spectrum. “U” indicates unidentified lines. Because radio telescopes use heterodyne receivers with multiplexing spectrometers, spectral resolution as high as 1 part in 108 can be achieved, particularly in cold, quiescent astronomical sources. This resolution is invaluable for chemical identification of molecules, and for investigations of velocity structure in astronomical objects. SOURCE: Lucy Ziurys, University of Arizona. are invaluable in investigating galactic chemical evolution and nucleosynthesis in stars. Maser action often occurs in certain molecules in star-forming regions and in envelopes of evolved stars, such as in SiO or CH3OH. Observations of maser lines provide information on small-scale structure and time variability of emitting sources. The 71-238 GHz region also covers the premier spectral windows for astrochemistry. Many new interstellar molecules are discovered by observations at these frequencies, as illustrated by the recent identification of CCP, PO, HSCN, AlO, and AlOH. It is naturally difficult to predict a priori the transition frequencies of any possible new molecule. Therefore, protecting given lines does not fully cover the science that comes from observations in these bands. 18

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of unknown origin; (2) The high-redshift (z) universe, including distant black-hole-powered radio galaxies and clusters—tools for understanding proto-galaxy collapse in the early Universe and the cosmological evolution of Dark Matter and Dark Energy, respectively—and path-finding studies of the Dark Ages at z > 30 (ν < 50 MHz), before stars turned on or galaxies formed; and (3) Acceleration, propagation, and turbulence in the interstellar medium, including the space distribution of galactic cosmic rays and supernova remnants together with scattering- and absorption-based probes of the magnetized interstellar plasma. Meteor scatter and sporadic E can have path loss as low 160 dB (for distances in the 800-2000 km range) at 30-50 MHz so that an EIRP of about –30 dBW will be at the interference (approx. –190 dBW sensitivity of the LWA) threshold levels of the LWA. If the radars radiate +20 dBW EIRP (100 watts) out to sea they will need to be sure their antenna backlobe is down by 50 dB to avoid interfering with the LWA in New Mexico. Recommendation: Unwanted emissions due to new radar allocations the 3-50 MHz range should be low enough to meet the levels of Recommendation ITU-R RA.769 in the Radio Astronomy Service bands at 13.36-13.41, 25.56-25.67 and 37.50-38.25 MHz. 29

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AGENDA ITEM 1.18: SECOND HARMONIC EMISSIONS INTO 4800-5000 MHZ Agenda Item 1.18 considers extending the existing primary and secondary radiodetermination-satellite service (space-to-Earth) allocations in the band 2 483.5-2 500 MHz in order to make a global primary allocation, and to determine the necessary regulatory provisions based upon the results of ITU R studies, in accordance with Resolution 613 (WRC 07). The primary concern for Radio Astronomy is second harmonic emissions into the 4800-4990 and 4990 to 5000 MHz bands. Nearly all centimeter wavelength radio telescopes operate in the 4800-5000 MHz band to study the continuum radio emission from stars, galaxies, quasars, gamma-ray bursts and other sources of galactic and extragalactic thermal and non thermal continuum radiation. If enacted in full, this agenda item could impact radio astronomy in the 4800-5000 MHz band as a result of second harmonic radiation. So, second harmonic radiation should be kept below the level given in Recommendation ITU-R RA.769 in the band 4800 MHz to 5000 MHz as addressed in 5.402: The use of the band 2483.5-2500 MHz by the mobile-satellite and the radiodetermination-satellite services is subject to the coordination under No. 9.11A. Administrations are urged to take all practicable steps to prevent harmful interference to the radio astronomy service from emissions in the 2483.5-2500 MHz band, especially those caused by second-harmonic radiation that would fall into the 4990-5000 MHz band allocated to the radio astronomy service worldwide. Recommendation: Second harmonic radiation emissions into the 4800-5000 MHz band should be kept below the level given in Recommendation ITU-R RA.769 as addressed in 5.402. 30

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AGENDA ITEM 1.19: SOFTWARE-DEFINED RADIO AND COGNITIVE RADIO SYSTEMS To consider regulatory measures and their relevance, in order to enable the introduction of software-defined radio and cognitive radio systems, based on the results of ITU R studies, in accordance with Resolution 956 (WRC 07). Resolution 956 (WRC-07), the impetus for WRC Agenda Item 1.19, considers implementation of software-defined and cognitive radio technologies. The primary concern with respect to this item is that any changes to spectrum regulation to implement these technologies must account for the unique requirements of RAS and EESS. RAS and EESS are receive-only services that require consistently and extraordinary low levels of interference in order to function productively; 1 these requirements are documented in multiple ITU Recommendations. 2 Recommendation: Any modification to existing methods of allocating or managing spectrum should not result in higher levels or additional instances of harmful interference in spectrum already allocated for Radio Astronomy Service and Earth Exploration-Satellite Service. Recommendation: Great care should be taken prior to enactment of new regulations in order to ensure that new uses of spectrum—especially those in frequencies adjacent to or harmonically-related to existing Radio Astronomy Service (RAS) or Earth Exploration-Satellite Service (EESS) allocations—do not result in increased levels of interference to RAS or EESS through unwanted emission. Recommendation: Representatives of the Radio Astronomy Service and Earth Exploration-Satellite Service spectrum management communities should be included in deliberations that might lead to the establishment of universal “beacon” or “pilot” channels, “dynamic databases,” and other technologies intended to facilitate “dynamic spectrum access” or dynamic changes in other emission characteristics including modulation type, bandwidth, and power levels. As noted in Resolution 956 (WRC-07), RAS and EESS facilities do not transmit, thus it is impossible for a radio system to discover these users of the spectrum without additional means. Engagement of the RAS and EESS communities early in the development of these technologies (and associated regulatory developments) will be important to identify these additional means, and will also increase the chances of identifying mutually-beneficial solutions. 1 National Research Council, Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses, The National Academies Press, Washington, D.C., 2010, pp. 79-90. 2 See ITU-R Recommendation RA-769; ITU-R Recommendation RS-1029; and other Recommendations are given in National Research Council, Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses, The National Academies Press, Washington, D.C., 2010, pp. 105-108. 31

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AGENDA ITEM 1.20: HAPS LINKS IN 5850 TO 7075 MHZ To consider[s] the results of ITU R studies and spectrum identification for gateway links for high altitude platform stations (HAPS) in the range 5 850-7 075 MHz in order to support operations in the fixed and mobile services, in accordance with Resolution 734 (Rev.WRC 07). RADIO ASTRONOMY SERVICE The primary concern for Radio Astronomy is the presence of two important spectral lines within this frequency range: Methanol at 6668.518 MHz and OH at 6035.093 MHz. Additionally, there is concern that HAPS-like satellites will be line-of-sight to a very large area. For example at 22 km altitude the radius of the line of sight coverage is about 530 km in radius and consequently unwanted emissions need to be low enough to meet the levels of Recommendation ITU-R RA.769 if HAPS platforms are deployed within range of radio astronomy observatories. 1 Observations of the spectral line of the methanol molecule at a rest frequency of 6668.518 MHz are critically important in the understanding of the structure of our galaxy. This structure is very difficult to determine because we live in the plane of our galaxy and view it edge on. The methanol line radiates as maser emission from the envelopes of newly formed massive stars throughout the galaxy. These maser stars act as precise beacons whose three dimensional coordinates and velocity vectors can be determined by high precision astrometry with very long baseline interferometry. Such precision astrometry cannot be achieved by optical space missions because of the effects of dust absorption in the galactic plane. Another spectral line in this band is the OH transition at 6035.093 MHz. It also radiates as a maser in the envelopes of massive stars and is particularly useful in measuring the magnetic field strengths in the envelopes of these stars. Recommendation: Unwanted emissions should be low enough to meet the levels of Recommendation ITU-R RA.769 in Radio Astronomy Service frequency allocations if high-altitude platform stations are deployed within range of radio astronomy observatories. Earth Exploration-Satellite Service The primary concern for EESS is Earth remote sensing satellites currently use, and will continue to use, spectrum near 6.8 GHz to measure soil moisture (SM) and sea surface temperature (SST). 2 NASA’s EOS Aqua carries the Japanese AMSR-E radiometer that observes a bandwidth of 350 MHz at 6.925 GHz (soon to be accompanied by the Japanese GCOM-W1’s AMSR-2 that also observes a bandwidth of 350 MHz at 6.925) and the Navy’s WindSat radiometer that observes a bandwidth of 130 MHz at 6.8 GHz. The U.S. Joint Polar-orbiting Satellite System (JPSS) will use band(s) between 5-8 GHz to monitor SST and SM, both of which strongly affect the weather and climate. Because of the microwave physics this frequency range is the best for measuring SST and is very practical for measuring soil moisture. International Footnote 5.458 urges “Administrations [to] bear in mind the needs of the Earth exploration-satellite (passive) and space research (passive) services in their future planning” of this frequency range. Indeed, actions affecting this frequency range should be considered carefully so its use by EESS (passive) is preserved. 1 Rygl, K, Brunthaler, A., Reid, M.J., Menten, K, van Langelde, H.J., and Xu, Y., “Trigonometric Parallaxes of the 6.7 GHz Methanol Masers,” Astronomy and Astrophysics, 2010, 511, A2; and Menten, K., “The Discovery of a new, very strong and widespread methanol maser line,” Astrophysical Journal, 1991, 380, L75. 2 National Research Council, Spectrum Management for Science in the 21st Century, The National Academies Press, Washington, D.C., 2010. 32

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Recommendation: Spectrum selected for high altitude platform stations gateway links should avoid frequencies used for Earth observation by current and planned remote sensing satellites in accordance with Footnote 5.458. 33

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AGENDA ITEM 1.21: 15.4-15.7 GHZ RADAR To consider a primary allocation to the radiolocation service in the band 15.4-15.7 GHz, taking into account the results of ITU-R studies, in accordance with Resolution 614 (WRC-07). 1 Radio Astronomy Service The primary concern is radar in the 15.4-15.7 GHz band could spill into the 15.35-15.40 GHz RAS/EESS band. The RAS band at 15.35-15.40 GHz is used extensively to study the origins of high energy jets driven by black holes in the centers of galaxies, which radiate copiously by the synchrotron process in this band. The nature of these jets and their connection to the evolution of galaxies is an important issue in modern astrophysics. If the radar has a peak power of +30 dBW EIRP then the received signal at 20 km is –67 dBW/m^2, so that the out-of-band emissions of the radar need to be below –89 dBc to meet the limit specified in Recommendation ITU-R RA.769 to avoid the radar causing direct interference in the RAS/EESS band. Airborne transmitters coming closer than 20 km would require even more stringent limits on unwanted emissions into the adjacent passive band. Recommendation: Radar in the 15.4-15.7 GHz band should have a sufficiently low level of unwanted emissions to avoid interference in the adjacent 15.35-15.40 GHz Radio Astronomy Service/Earth Exploration-Satellite Service band in accordance with the limits specified in Recommendation ITU-R RA.769. 1 Resolution 614 is to study, as a matter of urgency, the technical characteristics, protection criteria, and other factors to ensure that radiolocation systems can operate compatibly with systems in the aeronautical radionavigation and fixed-satellite services in the band 15.4-15.7 GHz, taking account of the safety nature of the aeronautical radionavigation service; to study, as a matter of urgency, the compatibility between the radiolocation service in the band 15.4-15.7 GHz and RAS in the adjacent band 15.35-15.40 GHz. 34

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AGENDA ITEM 1.25: ADDITIONAL MOBILE-SATELLITE SERVICE IN THE BANDS 4-16 GHZ To consider[s] possible additional allocations to the mobile-satellite service, in accordance with Resolution 231 (WRC 07). ITU-R studies are focusing on the following frequency bands for which detailed technical compatibility or sharing analysis are yet to be made (see Table 2.10). Radio Astronomy Service The primary concern for Radio Astronomy is that the frequency range 4-16 GHz contains the following RA bands: 4800-4990 MHz (secondary), 4990-5000 MHz (primary), 10.6-10.7 GHz (primary) and 15.35-15.4 GHz (primary). Nearly all centimeter wavelength radio telescopes operate in the 4800- 5000 MHz band to study the continuum radio emission from stars, galaxies, quasars, gamma-ray bursts and other sources of galactic and extragalactic thermal and non thermal continuum radiation. The downlink in the 5150-5250 MHz band is close to the 4990-5000 MHz passive band used for continuum studies of galactic and extragalactic sources. Recommendation: Satellite downlink transmissions should have low enough out-of-band emissions to minimize interference with radio astronomy based on Recommendation ITU-R RA.769. This applies to uplinks as well, though if well separated from observatory sites, uplinks are unlikely to cause interference. Earth Exploration-Satellite Service The primary concern for Remote Sensing is that the frequency range 4-16 GHz contains the 10.6- 10.7 GHz EESS (passive) allocation as well as the bands near 7 GHz in use by current assets. These bands are used for a number of EESS applications including observations of soil moisture, sea surface temperature, sea surface height, sea ice, snow, and precipitation. Measurement of these geophysical parameters is critically important to weather prediction, climate monitoring and understanding changes in the global water cycle. Current spaceborne radiometers observing Earth in 10.6-10.7 GHz suffer from interference making the data unusable in certain areas, e.g., over the Mediterranean Sea, due to satellite s- E transmissions reflected off the ocean surface.1 Additional passive bands of interest include the spectrum near 6.8 GHz to measure soil moisture (SM) and sea surface temperature (SST). (See also agenda item 8.2) NASA’s EOS Aqua carries the Japanese AMSR-E radiometer measuring in 350 MHz at 6.925 GHz and the Navy’s WindSat radiometer measures in 130 MHz at 6.8 GHz. The U.S. Joint Polar-orbiting Satellite System (JPSS) will use band(s) between 5-8 GHz to monitor SST and SM, both of which strongly affect the weather and climate. Because of the microwave physics this frequency range is the best for measuring SST and is very practical for measuring soil moisture. International Footnote 5.458 urges “Administrations [to] bear in mind the needs of the Earth exploration-satellite (passive) and space research (passive) services in their future planning” of this frequency range. Indeed, actions affecting this frequency range should be considered carefully so its use by EESS (passive) is preserved. 1 National Research Council, Spectrum Management for Science in the 21st Century, The National Academies Press, Washington, D.C., 2010, pp. 67-72. 35

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TABLE 2.10 Data from WMO Preliminary Position Paper, September 28, 2009 Frequency Band MSS Direction Meteorological Applications Concerned 4 400-4 500 MHz DL or UL 4 800-4 990 MHz UL 5 150-5 250 MHz DL 7 055-7 250 MHz DL Passive sensing 7 750-7 900 MHz UL MetSat 8 400-8 500 MHz UL 10.5-10.6 GHz DL, but UL might also be Passive sensing (adjacent band) considered 13.25-13.4 GHz DL Active sensing 14.8-15.35 GHz DL or UL NOTE: DL, downlink, UL, uplink. There are a number of active applications of EESS in the frequency range of interest, including 5.4 GHz which is used by the ESA ASCAT for ocean wind and ocean current measurement, and 13.4 GHz which has been used by NASA for ocean wind sensing. These sensors are used operationally in weather and storm prediction. Interference degrades the measurement accuracy, resulting in loss of coverage and adversely impacting forecasting capability. Other examples of active applications are spaceborne synthetic aperture radars (SARs) such as RADARSAT2 (5.355-5.455 GHz) and TerraSAR-X (9.05-10.05 GHz). Recommendation: Per International Footnote 5.458, “Administrations [are urged to] bear in mind the needs of the Earth exploration-satellite (passive) and space research (passive) services in their future planning” of this frequency range to protect current and future spaceborne observatories. 36

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AGENDA ITEM 8.1.1C: SOCIETAL BENEFIT Agenda Item 8.1.1C deals “with improving the recognition of the essential role and global importance of Earth observation radiocommunication applications and their societal benefits.” Humanity takes advantage of the natural emissions of terrestrial and astrophysical sources to increase understanding of our environment and our place in the Universe. Access to these faint tracers of key physical parameters is vital to our safety and insight. These incredibly sensitive passive sensors require protection from interference. The ITU has provided protection through its Regulations and Recommendations. It needs to continue (and improve) this recognition of the vital role of the passive observing services (RAS and EESS) into the future. The exponential growth of remote sensing technology in the recent past has collectively provided an enormous amount of information and insight. This has become a key means to understand the effects of changes in both the natural and artificial environment and to provide information for effective decision-making and resource management in many areas of our society and lives. In addition, remote sensing science and technology have economic benefits, both in job creation and in early warning of potentially disastrous and disruptive situations. As remote sensing observations continue, they are expected to yield revolutionary insights about our environment and serve as a catalyst to increase effective use of natural resources. The fields that benefit from Earth remote sensing are broad based and varied. Some of the key applications include the following: • Critical public safety needs are addressed using aviation, maritime, defense, and anti-collision radars. • Weather prediction and climate change benefit from global monitoring of clouds, precipitation, surface winds, moisture, temperature, aerosols, trace gasses and changes in glaciers and Earth’s vegetation canopy (biomass). • Weather forecasting and climate monitoring are vital for human health, welfare and security. They are also beneficial in daily outdoor activities, transportation, agriculture, and defense. They have reduced the impact on property and human life of extreme weather events such as hurricanes, droughts, tornados, and wildfires. • Detection of forest fires reduces both response time and damage. • Data on land use, planning and coastal monitoring benefits both developed and developing countries. • More effective management of natural resources is enabled by remote sensing data. • Spectral monitoring and management yield improved utilization and reduction in frequency interference for scientific, governmental, defense and commercial applications. • The availability of Earth remote sensing data increases the capabilities of scientific, government and commercial users. • Research and development efforts supporting observations in the passive spectral bands have and will likely continue to produce high-tech spinoffs that benefit our society. Astronomical observations transform our understanding of fundamental physics, the origin and evolution of the universe, and the place of humanity in the universe. To achieve these goals, astronomers, physicists and engineers have developed sensitive instruments and sophisticated software. In many instances these push the state of the art, not only for science but for practical applications in health, safety and commercial applications. As noted in the CORF Handbook, the ability to determine redshift, for example, “is directly related to the ability to cover the widest possible bandwidth in a search; therefore, it 37

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is important to preserve portions of the spectrum to allow this fundamental information to be measured.” 1, 2,3,4 Preservation of access to faint, naturally occurring signals found in the terrestrial and astrophysical environments through formal recognition of the passive observing services remains a vital role of humanity, through the ITU. Conclusion: Earth observation using radiocommunication frequencies has become a key means to understand the effects of changes in both the natural and artificial environment, and to provide information for effective decision-making and resource management in many areas of society and life. In addition, Earth science and observation technology have economic benefits, both in job creation and in early warning of potentially disastrous and disruptive situations. These benefits will continue, and increase as technology pushes humankind’s understanding of its environment even further. 1 National Research Council, Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses, The National Academies Press, Washington, D.C., 2010, pp. 26. 2 See also National Research Council, Spectrum Management for Science in the 21st Century, The National Academies Press, Washington, D.C., 2010, pp. 90-105. 3 National Research Council, Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses, The National Academies Press, Washington, D.C., 2010, pp. 26. 4 See also National Research Council, Spectrum Management for Science in the 21st Century, The National Academies Press, Washington, D.C., 2010, pp. 90-105. 38

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AGENDA ITEM 8.2: NEXT WRC Recommend[s] to the Council items for inclusion in the agenda for the next WRC, and to give its views on the preliminary agenda for the subsequent conference and on possible agenda items for future conferences, taking into account Resolution 806 (WRC 07). Secondary Allocation to EESS (passive) of a 200 MHz Bandwidth Located Between 6.425 and 7.250 GHz Recommendation ITU-R RS.1029 states that 200 MHz of bandwidth between 6.425 and 7.250 GHz is required for sea surface temperature and soil moisture remote sensing. Radio Regulations footnote 5.458 recognizes the current use of this frequency range for remote sensing of sea surface temperature and states, “Administrations should bear in mind the needs of the Earth exploration-satellite (passive) and space research (passive) services in their future planning of the bands 6.425-7.025 MHz and 7.075-7.250 MHz.” Recommendation: A secondary allocation for Earth Exploration-Satellite Service (passive) between 6.425 and 7.250 GHz should be sought to normalize the radio regulations with the current and planned practical passive use of the spectrum for Earth observation. Following the launch of NASA’s EOS Aqua in 2002 and Navy’s WindSat in 2003, radiometers have been passively using the spectrum near 7 GHz to measure soil moisture and sea surface temperature on a global basis. Table 2.11 lists current and future U.S. EESS passive sensors using this band. The satellites in Table 2.11 will have benefits that reach far beyond the countries that funded them. Soil moisture is a key factor in evaporation and transpiration at the land-atmosphere boundary. Due to the large amount of energy required to vaporize water, soil moisture has a large influence on both surface energy and carbon fluxes at Earth’s land surface. Sea surface temperature provides critical information on the ocean surface thermal state, which plays an important role in the transpiration of gases at the air-sea boundary. Such air-sea interactions are important in climate studies. Furthermore, since the density of water is determined by its temperature and salinity, sea surface temperature is a key determinant of waves and currents in response to external forces. Passive microwave measurements of sea surface temperature in the 7-GHz band “see through” nearly all clouds and precipitation. Such all- weather coverage permits measurement of the ocean surface during and after hurricanes and tropical cyclones, which often spawn cirrus clouds that block geostationary weather satellites from viewing the surface at visible and infrared wavelengths from 1 day to about a week. TABLE 2.11 EESS Passive Sensors Using the Spectrum Between 6.425 and 7.250 GHz Minimum Frequency Maximum Frequency Sensor Satellites (GHz) (GHz) WindSat Coriolis 6.737 6.863 AMSR-Ea EOS Aqua 6.750 7.100 MIS JPSS (under development) 6.450 6.800 a AMSR-2 on GCOM-W1, set for launch in early 2012, is a follow-on to AMSR-E and is planned to operate at two center frequencies of 6.925 and 7.3 GHz. See http://sharaku.eorc.jaxa.jp/AMSR/AMSR2_RA/documents/ GCOM_RA1_E.pdf; accessed on June 18, 2010. 39