3
Science Service Allocations

3.1
GENERAL CONSIDERATIONS

This chapter lists and discusses the science service spectrum allocations in the United States1 and their use. The Radio Regulations divides the world into three regions for spectrum allocation purposes. The United States is in Region 2 (see Figure 3.1).

3.1.1
Atmospheric Windows in the Radio Spectrum

The allocation of spectral bands for radio astronomy is based partly on the atmospheric windows available, as shown in Figure 3.2. Ground-based telescopes can observe only in the regions of the atmosphere that are not obscured. Below 50 GHz, there is a window between approximately 15 MHz and 50 GHz. Above 50 GHz, such radio windows occur at wavelengths around 3 mm (65-115 GHz), 2 mm (125-180 GHz), and 1.2 mm (200-300 GHz). At wavelengths shorter than 1 mm, the so-called submillimeter bands, the windows are less distinct, but clear ones exist at 0.8 mm (330-370 GHz), 0.6 mm (460-500 GHz), 0.4 mm (600-700 GHz), and 0.3 mm (800-900 GHz), as well as in other, smaller windows.

Furthermore, if Figure 3.2 showed absorption rather than transmission, the lines of particular importance to the Earth Exploration-Satellite Service (EESS) would be readily apparent: namely, the water lines at 22.235 and 183.1 GHz and the oxygen lines around 55-60 GHz and 118.75 GHz, as well as the available windows needed for comparison purposes, surface observations, and communications. Atmospheric absorption bands are used to measure atmospheric temperature and pressure profiles while using the windows to observe surface features, vegetation, and temperatures.

1

The U.S. and international spectrum allocation table and footnotes are available in the National Telecommunications and Information Administration’s Manual of Regulations and Procedures for Federal Radio Frequency Management (Redbook) at http://www.ntia.doc.gov/osmhome/redbook/redbook.html and in the Frequency Allocation Table at http://www.fcc.gov/oet/spectrum/table/.



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Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses 3 Science Service Allocations 3.1 GENERAL CONSIDERATIONS This chapter lists and discusses the science service spectrum allocations in the United States1 and their use. The Radio Regulations divides the world into three regions for spectrum allocation purposes. The United States is in Region 2 (see Figure 3.1). 3.1.1 Atmospheric Windows in the Radio Spectrum The allocation of spectral bands for radio astronomy is based partly on the atmospheric windows available, as shown in Figure 3.2. Ground-based telescopes can observe only in the regions of the atmosphere that are not obscured. Below 50 GHz, there is a window between approximately 15 MHz and 50 GHz. Above 50 GHz, such radio windows occur at wavelengths around 3 mm (65-115 GHz), 2 mm (125-180 GHz), and 1.2 mm (200-300 GHz). At wavelengths shorter than 1 mm, the so-called submillimeter bands, the windows are less distinct, but clear ones exist at 0.8 mm (330-370 GHz), 0.6 mm (460-500 GHz), 0.4 mm (600-700 GHz), and 0.3 mm (800-900 GHz), as well as in other, smaller windows. Furthermore, if Figure 3.2 showed absorption rather than transmission, the lines of particular importance to the Earth Exploration-Satellite Service (EESS) would be readily apparent: namely, the water lines at 22.235 and 183.1 GHz and the oxygen lines around 55-60 GHz and 118.75 GHz, as well as the available windows needed for comparison purposes, surface observations, and communications. Atmospheric absorption bands are used to measure atmospheric temperature and pressure profiles while using the windows to observe surface features, vegetation, and temperatures. 1 The U.S. and international spectrum allocation table and footnotes are available in the National Telecommunications and Information Administration’s Manual of Regulations and Procedures for Federal Radio Frequency Management (Redbook) at http://www.ntia.doc.gov/osmhome/redbook/redbook.html and in the Frequency Allocation Table at http://www.fcc.gov/oet/spectrum/table/.

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Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses FIGURE 3.1 The regions as defined in Article 5 of the Radio Regulations. The shaded part represents the Tropical Zone. SOURCE: National Telecommunications and Information Administration, Manual of Regulations and Procedures for Federal Radio Frequency Management (Redbook), May 2003 edition, revised January 2006. See http://www.itu.int/ITU-R/ for more information. 3.1.2 Note to the Reader Regarding Frequency Allocation Tables Because regulations, allocations, and footnotes can change, the reader is advised to consult the National Telecommunications and Information Administration’s (NTIA’s) Manual of Regulations and Procedures for Federal Radio Frequency Management (Redbook) or the Federal Communications Commission’s (FCC’s) FCC Online Table of Frequency Allocations, as well as the Radio Regulations, for the latest information. The Redbook can be found at http://www.ntia.doc.gov/osmhome/redbook/redbook.html, and the FCC’s document can be found at http://www.fcc.gov/oet/spectrum/table/fcctable.pdf. The information given in this chapter is current as of January 2006. Each of the following eight sections in this chapter begins with a table of allocations for a specified frequency range—allocations below 1 GHz (Table 3.1), between 1 and 3 GHz (Table 3.2), between 3 and 10 GHz (Table 3.3), between 10 and 25 GHz (Table 3.4), between 25 and 50 GHz (Table 3.5), between 50 and 71 GHz (Table 3.6), between 71 and 126 GHz (Table 3.7), and between 125 and 275 GHz (Table 3.8). The first column of each table lists the band allocations, and the fourth column elaborates on the scientific use of each band. In the second column, primary allocations are shown in capital letters (e.g., “RAS”), and secondary allocations appear in lowercase letters (e.g., “ras”). Footnotes to the tables indicate where the allocations in other regions differ. Parentheses around a science service—for ex-

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Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses FIGURE 3.2 Top: Atmospheric windows in the radio spectrum commonly used in the Radio Astronomy Service community. The transmission is appropriate for a site of 400-m elevation and a precipitable water vapor content of 1 mm. Courtesy of Lucy Ziurys, University of Arizona. Bottom: Atmospheric zenith opacity in the radio spectrum commonly used in the Earth Exploration-Satellite Service community. From A.J. Gasiewski and M. Klein, “The Sensitivity of Millimeter and Sub-millimeter Frequencies to Atmospheric Temperature and Water Vapor Variations,” Journal of Geophysical Research-Atmospheres, Vol. 13, pp. 17481-17511, July 16, 2000.

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Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses ample, “(ras)”—indicate that one or more footnotes in the ITU Radio Regulations and/or the U.S. Table of Frequency Allocations provide limited protection. Footnotes in the ITU Radio Regulations and the U.S. Table of Frequency Allocations that modify the allocations are noted in the third column of each table. A brief synopsis of each of these footnotes is given when it is first referenced in a table. Readers are advised to check for footnotes such as 5.340 and US211 that cover several bands. Appendix I spells out the acronyms used in Tables 3.1 through 3.8 and describes the ITU Radio Regulations and the U.S. Table of Frequency Allocations footnote designations (e.g., for 5.350, US211, G59, and NG101). 3.2 ALLOCATIONS BELOW 1 GHZ The bands, services, footnotes, and scientific observations for each band in the allocations below 1 GHz are presented in Table 3.1. 3.2.1 Solar Radio Bursts Radio observations made at frequencies below ~100 MHz also capture data on solar bursts. Occasionally, and frequently during sunspot maximum, dramatic radio bursts of several different characteristic types are generated in the Sun’s atmosphere. Such bursts are sometimes associated with solar flares, which are sudden, violent explosions in the Sun’s chromosphere. The radio bursts are observed from ~20 to ~400 MHz and are more intense at the lower frequencies. The high-energy particles ejected from the Sun during these bursts may interact with Earth’s ionosphere and the stratosphere. Such interactions cause severe interruptions in radio communications and power systems and can also have dangerous effects on aircraft flights above 15 km. Studies of radio bursts aim to enable the prediction of failures in radio communications and the forecasting of other effects. Knowledge of the high-energy particle ejections from the Sun is essential for space exploration missions, both manned and unmanned. Continuous monitoring of the Sun’s activity will remain a high priority for the foreseeable future. 3.2.2 Jupiter Radio Bursts Also significant is the peculiar nonthermal burstlike radiation from the giant planet Jupiter; this radiation is best observed at frequencies from ~15 to ~40 MHz. Extensive observations are being made at low frequencies in order to study this unusual radiation. It was observed by the Voyager spacecraft, but further ground-based studies are essential. 3.2.3 Interstellar Medium The low-frequency range below 1 GHz also has a great importance in the observations of both the thermal and nonthermal diffuse radiation in our own Milky Way Galaxy. Such galactic observations give information about the high-energy cosmic ray particles in our Galaxy and about their distribution, and also about the hot ionized plasma and star birth in the disk of our spiral Galaxy. In particular, the ionized interstellar clouds can be studied at low frequencies where the sources are opaque and their spectra approximate the Planck thermal radiation (blackbody) law. Such spectral observations can be used directly to measure the physical parameters of the radiating clouds, particularly their temperatures.

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Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses TABLE 3.1 Frequency Allocations Below 1 GHz: Bands, Services, Footnotes, and Scientific Observations Band (MHz) Services Footnotes Scientific Observations 13.36-13.41 RAS, FS1 5.149,2 G115,3 US342 Sun, Jupiter, interstellar medium, steep spectrum sources 25.55-25.67 RAS 5.149, US74,4 US342 Sun, Jupiter, interstellar medium, steep spectrum sources 37.50-38.25 FS, MS, ras5 5.149, US81,6 NG59,7 NG1248 Sun, Jupiter, interstellar medium, steep spectrum sources 73.00-74.60 RAS, FS,9 MS10 5.178,11 US74 Sun, interstellar medium, steep spectrum sources 137-138 SO, MetSat, SRS, MS12 5.204, 5.205, 5.206, 5.207, 5.208, US319, US230 NOAA (EESS) communications bands 150.05-153.0 RAS,13 FS, MS,14 (ras)15 5.149, 5.208A16 Sun, interstellar medium, steep spectrum sources, pulsars, continuum (single-dish mode) 322.0-328.6 RAS, FS, MS 5.149, G27,17 G10018 Deuterium, Sun, interstellar medium, steep spectrum sources, pulsars 400-406 MetAids (radiosonde), MetSat (S→ E), MS (S→ E), SRS (S→ E), MS (S→ E), EESS (E→ S) See NTIA Redbook 5.263, 5.264, US70, US329, US320, US324 NOAA (EESS) communications bands 406.1-410 RAS, FS, MS 5.149, 5.208A, US74, G5,19 G6,20 US117,21 US1322 Sun, interstellar medium, steep spectrum sources, pulsars 432-438 eess (active) 5.279A Biomass and soil measurements 460-470 See NTIA Redbook   NOAA (EESS) communications bands 608-614 RAS,23 mss24 5.149, 5.208A, US74, US24625 Sun, interstellar medium, steep spectrum sources, pulsars Several hundred such galactic clouds appear approximately as blackbodies at frequencies below ~100 MHz. The recombination lines that occur in this frequency range arise from very high energy levels, in which the electron orbits very far from the nucleus. In fact, these atoms are so large that the orbits of the outer electrons are affected by the electrons of other atoms in a measurable way, serving as a probe of the density of the gas. Recombination lines are further described in §3.3.8. 3.2.4 Deuterium The frequency range 322-328.6 MHz contains the hyperfine-structure spectral line of deuterium at 327.384 MHz. The study of this line has impacts on problems related to the origin of the universe and the cosmological synthesis of the elements. The recent detection of deuterium emission in the outer region of our Galaxy required months of integration time, with careful attention to mitigation of radio-frequency interference. Continuing study of the deuterium abundance in other parts of our Galaxy can further refine our understanding of the early universe.

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Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses NOTE: For definitions of acronyms and abbreviations, see Appendix I. For information about other features of this table, see §3.1.2, “Note to the Reader Regarding Frequency Allocation Tables.” 1Not in the United States. 2ITU RR footnote 5.149 urges administrations to take all practical steps to protect the RAS from other services in this band. 3U.S. (federal government services) footnote G115 limits protection for national defense and emergency needs. 4U.S. (all services) footnote US74 limits protection from transmitters in other bands. 5Primary in the United States from 38.00-38.25 MHz. 6US81 authorizes limited military use in the 38.00-38.25 MHz band. 7NG59 authorizes use of the 37.60-37.85 MHz band by power service utilities. 8NG124 authorizes low-power police radio on a non-interference basis. 9In Regions 1 and 3. 10In Regions 1 and 3. 11Additional allocation in some Caribbean nations to the fixed and mobile services on a secondary basis. 12MS is secondary in 137.025-137.175 MHz and 137.825-138.0 MHz. 13In Region 1. 14Except aeronautical. 15In Region 2, by S5.149. 165.208A provides footnote protection from space transmitters outside the band. 17G27 limits the FS and MS to military use. 18See G100 in Appendix B.3. 19G5 authorizes FS and MS for government nonmilitary agencies only. 20G6 allows military operations subject to local coordination. 21US117 limits transmitter power. 22US13 authorizes hydrological and meteorological fixed stations at specific frequencies. 23Footnote protection only in Regions 1 and 3. 24Except aeronautical; Earth-to-space only. 25US246 prohibits transmissions. 3.2.5 Steep-Spectrum Continuum Sources Most radio sources (such as radio galaxies, quasars, and supernova remnants) have characteristic nonthermal spectra produced by synchrotron emission from relativistic cosmic ray electrons moving in galactic-scale magnetic fields. As shown in Figures 2.1 and 2.2 in Chapter 2, these nonthermal sources typically have radio spectra with negative slopes of ~0.8 in a graph of log (flux density) versus log (frequency). Hence, such sources have higher radio flux densities at lower frequencies. The steepness of the spectrum depends on the energy of the electrons. As synchrotron sources age, the most energetic electrons are lost and the spectra steepen with time. At longer wavelengths, the spiraling electrons have increasingly higher cross sections for absorbing radiation, so that the emitted radiation is increasingly likely to be reabsorbed before escaping from the region. This causes turnovers in the spectra at low frequencies (see Figures 2.1 and 2.2), and the frequencies at which they occur are diagnostics of the emitting region. The low-frequency part of the spectrum is also where one finds the emission from highly redshifted radio sources, those that exist in the most distant parts of the universe.

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Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses The Arecibo Telescope in Puerto Rico, The Green Bank Telescope in West Virginia, the Very Large Array in the state of New Mexico, and the Very Long Baseline Array (VLBA)—a system of 10 radio telescope antennas positioned from Hawaii to the U.S. Virgin Islands—operate in these bands, as well as the Giant Metrewave Radio Telescope (GMRT) in India and the Westerbork Array in the Netherlands. High-resolution observations of radio galaxies and quasars have also been made with the GMRT using the method of lunar occultations, which uses the lunar disk to eclipse distant radio sources as they move across the sky. From such occultations, it has been possible to determine the shapes and positions of many extragalactic radio sources with very high accuracies, on the order of 1 arc second. 3.2.6 Pulsars One of the most interesting and significant discoveries in radio astronomy has been the detection of pulsars, for which Antony Hewish was awarded the Nobel Prize in physics in 1974. The understanding of stellar evolution has been advanced by providing a method of studying these rapidly rotating, highly magnetized neutron stars. Pulsars’ extreme magnetic, electric, and gravitational fields, impossible to reproduce in laboratories on Earth, allow observations of matter and radiation under such conditions. Pulsars now provide the most accurate timekeeping, surpassing the world’s ensemble of atomic clocks for long-term time stability. Pulsars are understood to be highly condensed neutron stars that rotate with a period as short as a millisecond. Such objects are produced by the collapse of the cores of massive stars during the catastrophic explosions known as supernova outbursts. The radio spectra of pulsars indicate a nonthermal mechanism, perhaps of synchrotron emission type. Observations have shown that the pulsars emit strongest at frequencies in the range from ~50 to 600 MHz. Hence, many observations are being performed at such frequencies. However, important observations and surveys are being conducted at frequencies up to 10 GHz. The discovery and the study of pulsars during the past two decades have opened up a major new chapter in the physics of highly condensed matter. The study of neutron stars with densities on the order of 1014 g/cm3 and with magnetic-field strengths of 1012 gauss has already contributed immensely to our understanding of the final stages of stellar evolution and has brought us closer to understanding black holes (which are thought to be the most highly condensed objects in the universe). Low-frequency bands 6-8 GHz are indeed important for pulsar observations, but exclusive bands in this range are not allocated. The Nobel Prize in physics in 1993 was awarded to Russell A. Hulse and Joseph H. Taylor, Jr., “for the discovery of a new type of pulsar, a discovery that has opened up new possibilities for the study of gravitation.”2 Binary pulsars have provided the best experimental tests of predictions of the theory of general relativity and strong evidence for the existence of gravitational radiation. Careful analysis of pulse timing residuals led to the startling discovery by radio astronomers Aleksander Wolszczan and Dale Frail in 1991, and confirmed in 1994, that pulsars can have planetsized bodies in orbit around them—the first detection of extrasolar planets. Pulsars are also diagnostics of the interstellar medium’s density and magnetic field. Continuum bands, particularly those at frequencies below 3 GHz, are most valuable for these studies. 2 Located at http://nobelprize.org/nobel_prizes/physics/laureates/1993/press.html, accessed September 14, 2006.

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Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses 3.3 BANDS BETWEEN 1 AND 3 GHZ In addition to the bands listed in Table 3.2, scientific use is also made of the 1675-1690 MHz Meteorological Aids Service (MetAids) band; the 1215-1300 MHz EESS active band, which is used for synthetic aperture radar (SAR) missions; and the Global Positioning System (GPS) bands at 960-1215 MHz, 1215-1300 MHz, and 1559-1610 MHz. 3.3.1 Neutral Atomic Hydrogen One of the most important spectral lines at radio wavelengths is the 21 cm line (1420.406 MHz), corresponding to the F = 1 → 0 hyperfine transition of neutral atomic hydrogen (HI). Radio observations of this line have been used since its discovery in 1951 to study the structure of our Galaxy and those of other galaxies. Because of Doppler shifts owing to the distance and motion of the hydrogen clouds that emit this radiation, the frequency for observing this line emission ranges from below 1 GHz to ~1430 MHz. Numerous and detailed studies are being made of the HI distribution in our Galaxy and in other galaxies. Such studies are being used to investigate the state of cold interstellar matter; the dynamics, kinematics, and distribution of the gas; the rotation of our Galaxy and of other galaxies; and the masses of other galaxies. The HI emission is relatively strong and, with current receiver sensitivity, such emission is detectable from any direction in our Galaxy and from a very large percentage of the nearby galaxies. The 1330-1400 MHz band is important for observations of redshifted HI gas from distant external galaxies. Such observations of redshifted HI have been made in a quasi-continuous range of frequencies down to 1260 MHz. Below this frequency, detections have been made at individual, isolated frequencies. Observations of HI below 1330 MHz have been limited in the past by spectrometer bandwidths, dynamic range, and limitations of sampling (dump time). Studies of the evolution of the HI mass function with cosmic time will require observations below 1260 MHz and are being proposed for systematic and concerted studies. As radio telescopes become more powerful, it will be possible to detect more-distant, and therefore more-redshifted (and therefore younger) galaxies. This increase in capability will allow astronomers to study how galaxies evolve. 3.3.2 Lines of Hydroxyl The study of hydroxyl (OH) is of great interest for investigating the physical phenomena associated with the formation of protostars and the initial stages of star formation. 3.3.2.1 Thermal Emission The OH molecule has been observed widely in our Galaxy in the four hyperfine components of the ground-state lambda-doubling transitions at 1665, 1667, 1612, and 1720 MHz. OH has been detected in thermal emission and absorption in several hundred different molecular complexes in our Galaxy. Thermal OH emission, which predominates in the low-density envelopes of molecular clouds, is the principal means for studying these envelopes. In addition, the two oppositely circularly polarized components become slightly separated in frequency in the presence of a magnetic field. This so-called Zeeman effect is the only way to measure the strength of the magnetic field in these regions. The magnetic field may play a major role in the dynamics of the gas.

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Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses TABLE 3.2 Frequency Allocations Between 1 and 3 GHz: Bands, Services, Footnotes, and Scientific Uses Band (MHz) Services Footnotes Scientific Use 1300-1350 AeRNS,1 rls, (ras) 5.149,2 5.337,3 G24 Extragalactic HI,5 recombination lines 1350-1400 FS,6,7 MS,8,9 LMS,10 RLS, (ras), (srs),11 (eess)12 5.149, 5.334,13 5.338,14 5.339,15 US311,16 US350,17 US351,18 G2, G27,19 G11420 Extragalactic HI, recombination lines 1400-1427 RAS, EESS (passive), SRS (passive) 5.340,21 5.341,22 US74, US246 Galactic and local extragalactic HI, recombination lines, radio source spectra, galactic continuum 1559-1610 AeRNS, RNSS (S→ E) and (S→ S) 5.341, 5.355,23 5.359,24 G12625 Extragalactic OH masers 1610-1610.6 MSS (E→ S), AeRNS, RDSS (E→ S),26 (ras) 5.341, 5.355, 5.359, 5.363,27 5.364,28 5.367,29 5.370,30 5.371,31 5.372,32 US208,33 US260,34 US31935 Extragalactic OH 1610.6-1613.8 RAS, MSS (E→ S), AeRNS, RDSS (E→ S)36 5.149, 5.341, 5.355, 5.359, 5.363, 5.364, 5.367, 5.369, 5.370, 5.371, 5.372, US319 OH 1660-1660.5 MSS (E→ S), RAS 5.149,37 5.341, 5.351,38 5.376A39 OH 1660.5-1668.4 RAS, SRS (passive), fs, ms (except aems) 5.149, 5.341, 5.379,40 5.379A,41 US74,42 US246 OH 1668.4-1670 RAS, MetAids,43 FS,44 MS (except Ae)45 5.149, 5.341, US74, US9946 OH 1670-167547 MetAids,48 FS,49 MetSat (S→ E), MS (except Ae)50 5.341, US21151 OH 1690-1700 MetAids,52 MetSat (S→ E),53 MSS (E→ S),54 fs,55 ms (except Ae),56 (eess) 5.289,57 5.341, 5.382,58 US211   1700-1710 FS, MetSat (S→ E), MS (except Ae),59 MSS (E→ S),60 (eess) 5.289, 5.341, 5.384,61 G11862   1718.8- 1722.263 FS, MS, ras 5.149, 5.341, 5.385,64 US25665 OH 2025-2110 SpaceOps, EESS (S→ E, S→ S), FS,66 MS,67 SRS (S→ E, S → S) 5.391,68 5.392,69 US90,70 US222,71 US346,72 US34773   2110-212074 FS, MS, SRS (deep S→ E) US25275   2200-2290 SRS (deep S→ E, S→ S), EESS (S→ E, S→ S), FS,76 MS,77 SRS (S→ E, S→ S) 5.391,78 5.392,79 US30380 Deep space downlinks, VLBI 2290-2300 FS, MS, SRS81     2310-2360 ms, rls, fs, BS US33882 Radar astronomy83 2640-2655 srs (passive), eess (passive), FS, MS, FSS, BSS 5.33984 Extragalactic radio sources, galactic continuum

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Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses Band (MHz) Services Footnotes Scientific Use 2655-2690 ras, srs (passive), eess (passive), FS, FSS,85 MS, BSS, MSS 5.149, US205,86 US269,87 NG47,88 NG101,89 NG10290   2690-2700 RAS, EESS (passive), SRS (passive) 5.340, 5.413,91 US74, US246   NOTE: For definitions of acronyms and abbreviations, see Appendix I. For information about other features of this table, see §3.1.2, “Note to the Reader Regarding Frequency Allocation Tables.” 1In the United States only. 25.149 urges administrations to take all practical steps to protect the RAS from other services using the band 1330-1400 MHz. 35.337 limits ANS to ground-based radars and airborne transponders activated by these radars. 4Government radiolocation is limited to the military services. 5HI, neutral atomic hydrogen. 6In Region 1 only. 7Secondary from 1390 to 1395 MHz and no allocation from 1395 to 1400 MHz in the United States. 8In Region 1 only. 9Secondary from 1390 to 1395 MHz and no allocation from 1395 to 1400 MHz in the United States. 10In the United States only from 1395 to 1400 MHz. 111370-1400 MHz only. 121370-1400 MHz only. 135.334, in Canada and the United States, adds the Aeronautical Radionavigation Service on a primary basis between 1350 and 1370 MHz. 145.338 allows existing installations of the radionavigation service in certain countries in eastern Europe to continue to operate in the band 1350-1400 MHz. 155.339 authorizes passive EESS and SRS in the 1370-1400 MHz band. 16US311 provides partial geographic protection only from 1350 to 1400 MHz. 17US350: LMS is limited to medical telemetry and telecommand operations. 18US351: Government operations are on a noninterference basis with nongovernment operations. 19G27 limits the FS and MS to military use. 20G114 authorizes space-to-Earth relay of nuclear burst data by the FSS and MSS in the 1369.05-1381.05 MHz band. 215.340 prohibits all emissions in this band. 225.341 makes note of SETI. 235.355 adds FS on a secondary basis in certain countries. 245.359 adds FS on a primary basis in certain counties but urges administrations to make no additional allocations. 25G126 allows addition of differential GPS on a primary basis. 26Primary in Region 2, secondary in Region 3, not in Region 1. 275.363 adds AeRNS on a primary basis in Sweden. 285.364 limits transmitter power and requires coordination. 295.367 adds AeMS(route) on a primary basis. 305.370: RDSS is secondary in Venezuela. 315.371 adds RDSS on a secondary basis in Region 1. 325.372 protects the RAS in the band 1610.6-1613.8 MHz from the RDSS and MSS. 33US208 states that sharing criteria and techniques need to be developed. 34US260 authorizes AeMS when it is an integral part of the ARS. 35US319 limits federal government use. 365.364 limits transmitter power and requires coordination. 375.149 urges protection of RAS when making assignments to other services in the band 1660-1670 MHz. 385.351 forbids feeder links. 395.376A protects the RAS from the MSS Earth stations. 405.379 provides additional secondary allocation to MetAids in certain countries. 415.379A urges further protection to the RAS in the 1660.5-1668.4 MHz band. 42US74 limits the protection to the RAS.

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Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses 43In the United States for radiosondes. 44Except in the United States. 45In the United States for radiosondes. 46US99 requires the advance notification of use of radiosondes in the 1668.4-1670 MHz band. 47Became mixed-use spectrum in the United States in January 1999. 48In the United States for radiosondes. 49Except in the United States. 50Except in the United States. 51US211 urges protection of adjacent RAS bands. 52US99 requires the advance notification of use of radiosondes in the 1668.4-1670 MHz band. 53US99 requires the advance notification of use of radiosondes in the 1668.4-1670 MHz band. 54In Region 2, except in the United States. 55US99 requires the advance notification of use of radiosondes in the 1668.4-1670 MHz band. 56US99 requires the advance notification of use of radiosondes in the 1668.4-1670 MHz band. 575.289 allows EESS (S→E) transmissions subject to not causing harmful interference to other services in this band. 585.382 adds other primary services in certain countries. 59US99 requires the advance notification of use of radiosondes in the 1668.4-1670 MHz band. 60In Region 2, except in the United States. 615.384 adds SRS (S→E) on a primary basis in India, Indonesia, and Japan. 62G118 limits government use of FS in this band. 63Within the larger band of 1710-1930 MHz by S4.149. 645.385 provides a secondary allocation to the RAS. 65US256 urges consideration of the RAS by other services in specific geographic areas. 66In the United States, nongovernment only. 67In the United States, nongovernment only. 685.391 excludes high-density mobile systems. 695.392 limits (S→S) in the SpaceOps, EESS, and SRS. 70US90 limits the pfd at the surface of Earth from SpaceOps, EESS, and SRS. 71US222 authorizes GOES (S→S) transmissions from Wallops Island, Virginia; Seattle, Washington; and Honolulu, Hawaii, in the band 2025-2035 MHz. 72US346 establishes rules for coexistence of government SpaceOps, EESS, and SRS with new broadcasting and TV services. 73US347 permits EESS and SRS (E→S) and (S→S) transmissions on a case-by-case noninterference basis. 74To be auctioned by September 30, 2002. 75US252 also allocates this band to SRS deep space (E→S) transmissions from Goldstone, California. 76In the United States, line of sight only. 77In the United States, line of sight only including aeronautical telemetry, but excluding flight testing of manned aircraft. 785.391 excludes high-density fixed service. 795.392 urges all practical steps to avoid interference from (S→S) operations in SpaceOps, SRS, and EESS. 80US303 authorizes the SRS, SpaceOps, and EESS to transmit to the TDRSS in the band 2285-2290 MHz on a case-by-case basis, subject to pfd limitations. 81Deep space, space to Earth. 82US338 requires coordination of all Wireless Communications Services in the band 2305-2320 MHz within 50 km of Goldstone, California. 83The Goldstone Solar System Radar operates at 2320 MHz. 845.339 adds the EESS and SRS in this band on a secondary basis. 85Except in Region 1. 86US205 prohibits troposcatter radar. 87US269 urges consideration of radio astronomy in the 2690-2700 MHz band. 88NG47 authorizes other special allocations. 89NG101 limits BSS. 90NG102 limits FSS. 915.413 mirrors US269.

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Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses 3.7 BANDS BETWEEN 50 AND 71 GHZ The bands, services, footnotes, and scientific observations for each band in the allocations between 50 GHz and 71 GHz are presented in Table 3.6. 3.7.1 Atmospheric Temperature Profiling Retrieval of the atmospheric temperature profile using passive sounding in the ~50-62 GHz region uses the multitude of spin-rotational O2 transitions in this region. Atmospheric attenuation varies from ~1 dB near ~50 GHz for clear atmospheric conditions to >200 dB at nadir for selected frequencies within ~58 to ~62 GHz. This characteristic provides the ability to estimate the atmospheric temperature within a specific altitude region by a careful selection and control of channel frequency. Atmospheric temperature profiles can be measured with an uncertainty of ~1 K with ~1-1.5 km altitude resolution to support a large variety of operational and scientific applications. The same oxygen resonance frequency that enables these measurements also leads to the strong absorption of terrestrial anthropogenic emissions, so that in many (albeit not all) cases the spectrum from ~58 to ~62 GHz can be shared with terrestrial active systems without interference. Atmospheric profiles of temperature from polar-orbiting satellites are required to initialize the current and emerging global ocean-atmosphere models. These models provide essential global meteorological and oceanographic predictions for many civil and military applications. High profile-measurement accuracies are essential for proper operation and input for prediction models. For example, it has been shown that for temperature profile inputs not meeting 1 K to 3 K (depending on altitude) uncertainty, the profile data corrupt the model rather than increase its capability to forecast. Observational errors, usually on smaller scales, amplify the model error and, through nonlinear interactions, gradually spread to longer scales, eventually destroying forecast skill. In previous studies, numerical models using data with a standard deviation of 0.5°C at all levels had an exponential error growth with a doubling time of about 2.5 days. Similar results were found for other data types (i.e., winds, moisture, and so on), with forecast errors as high as 20 to 30 percent. Atmospheric circulation is the main driver of regional changes in near-surface wind, temperature, precipitation, soil moisture, and other surface variables. These variables constrain the ability to make use of Earth’s resources and sustain humanity’s existence. Variations in these variables are strongly related through large-scale features of the atmospheric circulation as well as through interactions involving land and ocean surfaces. Atmospheric circulation is in turn dependent on the variables that define its structure and on dynamics such as wind speed and direction, temperature, humidity, and geopotential height. Two well-known examples of large-scale features are the El Niño-Southern Oscillation and the North Atlantic Oscillation, both of which are a product of global-scale climate fluctuations. Evidence from satellites globally observing associated changes in atmospheric variables may enhance the understanding of the specific relationships between surface and atmospheric variables and provide a better basis for validation of those relationships. Currently, atmospheric temperature profiles are measured using LEO satellite microwave sounders. A number of present-day technological developments are enabling the future deployment of a geostationary orbiting microwave temperature sounder. 3.7.2 Mesospheric Temperature Profile Within the ~50 to 62 GHz O2 complex, spectrum near the strongest oxygen transitions (e.g., 9+ and 7+) is used to measure temperature profiles in the upper atmosphere from ~40 to ~90 km in altitude. The

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Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses TABLE 3.6 Frequency Allocations Between 50 and 71 GHz: Bands, Services, Footnotes, and Scientific Uses Band (GHz) Services Footnotes Scientific Use 50.2-50.4 EESS (passive), FS,1 MS,2 SRS (passive) 5.340,3 5.555A,4 US2635 Temperature profiling 51.4-52.6 FS,6 MS,7 EESS8 (passive), SRS9 (passive), RAS10 5.55611   1-3 52.6-54.25 EESS (passive), SRS (passive) 5.340, 5.556, US24612 Temperature profiling, interstellar O2 54.25-55.78 EESS (passive), ISS, SRS (passive) 5.556B,13 909,14 US26315   54.25-56.9 EESS (passive), FS, ISS, MS, SRS (passive) 5.556A,16 5.557,17 5.558,18 US26319   56.9-57 EESS (passive), FS, ISS, MS, SRS (passive) 5.557, US26320   57-58.2 EESS (passive), FS, ISS, MS, SRS (passive) 5.556A, 557, US26321   58.2-59 EESS (passive), FS,22 MS,23 SRS (passive), RAS24 5.547, 5.556, US246 Interstellar O2 59.0-59.3 EESS (passive), FS, ISS, MS, RLS, SRS (passive) 5.556A, 5.558, 5.559, US353   NOTE: For definitions of acronyms and abbreviations, see Appendix I. For information about other features of this table, see §3.1.2, “Note to the Reader Regarding Frequency Allocation Tables.” 1In the United States only. 2In the United States only. 35.340 prohibits all emissions. 45.555A allowed FS and MS as primary until July 1, 2000. 5US263 cancels protection of EESS and SRS from FS and MS. 6Except in the United States. 7Except in the United States. 8Only in the United States. 9Only in the United States. 10Only in the United States. 115.556 notes that radio astronomy observations may be carried out under national arrangements. 12US246 forbids all emissions. 135.556B adds MS on a low-density basis in Japan. 14Old series international footnote 909 allows AeMS subject to not causing harmful interference to ISS. 15US263 cancels protection of EESS and SRS from FS and MS. 165.556A limits use of this band by ISS. 175.557 adds RLS on a primary basis in Japan. 185.558 allows AeMS subject to not causing interference to ISS. 19US263 cancels protection of EESS and SRS from FS and MS. 20US263 cancels protection of EESS and SRS from FS and MS. 21US263 cancels protection of EESS and SRS from FS and MS. 22Except in the United States. 23Except in the United States. 24In the United States only.

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Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses Defense Meteorological Satellite Program Special Sensor Microwave Imager Sounder will use frequencies between ~60.4 and 61.2 GHz and a separate channel near 63 GHz to obtain such mesospheric temperature profiles. Splitting of the strong O2 transitions by Earth’s magnetic field provides vertical response (or, weighting) functions that depend on the polarization of the received signal. 3.8 BANDS BETWEEN 71 AND 126 GHZ In addition to the bands listed in Table 3.7, the 78.00-79.00 GHz EESS active band is to be used for cloud monitoring and should be specifically listed rather than being relegated to a footnote, since it is a primary allocation. The spectrum within 102 and 126 GHz is not entirely allocated to EESS passive, but rather is broken into 102-105 GHz, 105-109.5 GHz, 109.5-111.8 GHz, 114.25-116 GHz, 116-119.98 GHz, and 119.98-122.25 GHz segments with different sharing services. EESS passive service is allocated only in the 109.5-111.8 GHz and 114.25-122.25 GHz bands. Per NTIA’s Redbook, even the Radio Astronomy Service allocation is fragmented: primary between 76 and 77.5 GHz, secondary from 77.5 to 78 GHz, primary between 78 and 116 GHz. The fragmentation of the 71-106 GHz spectral region is unfortunate and should be addressed at future World Radiocommunication Conferences. 3.8.1 Interstellar Molecular Lines Since there is relatively little absorption from atmospheric O2 and H2O, the 3 mm band between 65 and 115 GHz is perhaps one of the best high-frequency regions for both continuum and line observations of celestial objects. In particular, this band contains the fundamental (J = 1 → 0), or lowest-energy, transition of most common interstellar molecules, including CO, HCO+, HCN, CCH, CN, HNC, HCO, HNO, H2CO, and N2H+. More than 100 molecules have been detected in this frequency range, as have 25 different isotopic species. These also include favorable transitions of such simple molecules as SO, SO2, SiO, SiS, and MgNC and such complex molecules as CH3CH2OH, CH3CH2CN, and CH3OCH3. Two vibrational states of the transitions of SiO fall in this range; SiO is one of the few molecules TABLE 3.7 Frequency Allocations Between 71 and 126 GHz: Bands, Services, Footnotes, and Scientific Uses Band (GHz) Services Footnotes Scientific Use 72.77-72.91 FS, FSS (E→ S), MS, MSS (E→ S), RAS1 5.149,2 5.556,3 US2704 HC3N (important lines at 72.039 GHz for DCO+ and 72.415 GHz for DCN) 74-75.5 FS, FSS (S→ E), MS, srs5 (S→ E) US2976 HCNH+, N2 O, H2 CO 75.5-76 AeMS, AeMSS, srs7 (S→ E)     76-81 RAS (except secondary between 77.5-78), RLS, aems,8 aemss,9,10 srs11 (S→ E) 5.56012 HDO 81-84 RAS, FS, FSS (S→ E), MS, MSS (S→ E), srs13 (S→ E)   C3H 2, HC3N 84-86 RAS, FS, MS, BS, BSS, (ras) US21114 NH2 D, CH3CCH 86-92 EESS (passive), RAS, SRS (passive) 5.340,15 US74,16 US24617 SiO, H13CO+, HCO+, HCN, CCH, HNC, CH3CN, HC15N, H 13CN, HN13C, HCO

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Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses Band (GHz) Services Footnotes Scientific Use 92-94 FS, FSS (S→ E), MS, RLS, RAS 5.149, 5.556 13CS, N2H+ , AlNC 94-94.1 EESS (active), RLS, SRS (active), RAS 5.56218 Cloud radar 95-100 MS, MSS, RNS, RNSS, RAS19 5.149, 5.55520 CS, SO, C34S, MgNC 100-102 RAS, EESS (passive), FS,21 MS,22 SRS (passive) 5.341,23 US246 Extragalactic CO, HC3N 102-105 FS, FSS (S→ E), MS,24 RAS25 5.341, US211 CH3CCH 105-116 EESS (passive), RAS, SRS (passive) 5.340, 5.341, US74, US246 SO, CN, CO, 13CO, C18O, C17O, 13CN 116-119.98 EESS (passive), FS, ISS, MS, SRS (passive) 5.341, 5.558, US211, US263   119.98-120.02 EESS (passive), FS, ISS, MS, SRS (passive), aems 5.341, US211, US263   120.02-126 EESS (passive), FS, ISS, MS, SRS (passive) 5.138,26 US211, US26327 Temperature profiling NOTE: For definitions of acronyms and abbreviations, see Appendix I. For information about other features of this table, see §3.1.2, “Note to the Reader Regarding Frequency Allocation Tables.” 1In the United States only. 25.149 urges protection of RAS in this band. 35.556 allows RAS under national arrangements. 4US270 adds RAS to this band within the larger 71-74 GHz band. 5Except in the United States. 6US297 allows feeder links for BS. 7Except in the United States. 8Primary in the United States between 77.5 and 78 GHz. 9Primary in the United States between 77.5 and 78 GHz. 10In the United States only above 77 GHz. 11Primary in the United States between 77.5 and 78 GHz. 125.560 allows radars on space stations to be operated between 78 and 79 GHz on a primary basis for EESS and SRS. 13Except in the United States. 14US211 urges additional protection to RAS from adjacent bands. 155.340 prohibits all emissions. 16US74 limits protection of RAS from extraband radiation. 17US246 prohibits all emissions. 185.562 limits EESS and SRS to spaceborne cloud radars. 195.555 adds RAS as primary between 97.88 and 98.08 GHz. 205.555 adds RAS as primary between 97.88 and 98.08 GHz. 21Except in the United States. 22Except in the United States. 235.341 draws attention to SETI research in this band. 24Except in the United States. 25In the United States. 265.138 allows ISM applications subject to special agreements. 27US263 specifies that EESS and SRS will not be protected from FS and MS.

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Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses showing maser emission and the only one showing strong maser emission in an excited vibrational state. N2H+, HCS+, HCNH+, and HCO+ are vitally necessary participants in the ion-molecule reactions believed to be key in the formation of many other molecules in the interstellar gas. Furthermore, some molecules have several isotopic species in this range, so that isotopic abundance ratios can be studied. As an example, the basic molecule HCN has the isotopic species H12C14N, H3C14N, and H12C15N in the 86-92 GHz range, and all have been observed in the interstellar gas. It is clear that this region of the millimeter spectrum will remain one of the most-used for radio astronomy. 3.8.2 Carbon Monoxide The discovery of interstellar CO at 115.271 GHz has been of fundamental significance for the subject of astrochemistry. This is primarily because CO is a relatively stable molecule compared with other molecules discovered in the interstellar medium, and also because CO seems to be very abundant and exists almost everywhere in the plane of our Galaxy as well as in a number of other galaxies. Studies have yielded new information on the distribution of gas in spiral galaxies. Allowance for Doppler shifts characteristic of nearby and even distant galaxies is essential for adequate protection of radio spectral lines. Because the CO molecule is so ubiquitous and therefore present under nearly all physical and chemical conditions, its emission is the principal tool available to astronomers today for the study of the star-forming gas in the Milky Way Galaxy, and even in quite distant galaxies. CO studies give information about disks around forming stars and, in the future, with the expansion of millimeter-wave interferometer instruments, they may tell of the conditions for planet formation. Furthermore, CO emission studies reveal the presence of bursts of star formation activity in nearby and, in some cases, distant galaxies. These bursts have recently been related to collisions between galaxies and possibly to the formation of massive black holes and quasars. CO lines are also used to measure the mass loss rates from late-type stars. The 100-102 GHz band is used for radio astronomy observations of redshifted CO in distant galaxies. The 200-300 GHz band contains the second available rotational line of carbon monoxide (12C16O), together with its isotopic variants 13C16O and 12C18O. These are very strong and important lines both within our Galaxy and in distant galaxies. In combination with the first lines in the 106-116 GHz band, they permit the determination of the physical characteristics of the gas within the galaxies. The coverage for 12C16O extends to galaxies at velocities of 2000 km/s, but it should be much greater in order to give protection to the work of learning about the structure and evolution of much more distant galaxies in the future. 3.8.3 Isotope Ratios One important use of molecular lines is the study of isotope ratios, in particular, the 12C/13C, 16O/ 18O, and 32S/34S ratios. These ratios give important insight into theories of nucleosynthesis in stars and models of star-formation rates and the relative masses involved, that is, galactic chemical evolution. The important molecules in this context are 12CO, 13CO, and 18CO; 12CN and 13CN; and 12CS, 13CS, and C34S. The fundamental transitions of CO and CN and their isotopomers are in the 3 mm band, as well as favorable lines of CS. All of these species are important isotopic tracers. Molecules can also be used to investigate deuterium/hydrogen ratios. Because of chemical fractionation, very high deuterium/hydrogen ratios are found in certain interstellar molecules as a result of ion-

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Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses molecule chemistry. DCN and DCO+ are important tracers in this context. Their lowest-energy spectral transitions lie near 72 GHz. 3.8.4 Interstellar and Circumstellar Chemistry The 3 mm band, along with the 2 mm window, is particularly relevant to studies of interstellar chemistry, as these bands contain favorable transitions of most known molecules. As mentioned, species of interest include molecular ions such as HCO+ and HCNH+, the free radicals CN and CCH, and a large number of organic molecules, including C3H2, CH3OH, CH3CH2CN, CH3COCH3, and CH3OCHO. Also, the spectral lines originating from long-chain carbon species such as C3H, C3N, C4H, C7H, C8H, and so on are prominent in these bands, as well as those of silicon-, magnesium-, and aluminum-bearing molecules (SiS, SiC2, SiC3, MgCN, AlCl, AlNC, and so on). The long-chain molecules and the refractory species play significant roles in the chemistry of circumstellar envelopes of late-type stars. 3.8.5 Astrobiology Some theories posit that interstellar chemistry may have supplied the prebiotic compounds essential for terrestrial life. Consequently, establishing the inventory of organic molecules in interstellar gas is of interest to the study of the origin of life. Because organic molecules have many favorable transitions at millimeter wavelengths, this spectral region is crucial for the identification of such species. The 2 and 3 mm spectral regions have been the prime wavelength regions for the detection of organic molecules. Many possible new organic compounds may be identified in interstellar gas. It is important to recognize that new frequencies are regularly becoming available for possible new molecules, and hence broadband protection of the 2 and 3 mm windows is desirable. 3.8.6 Atmospheric Temperature Profile The atmospheric temperature profile can be derived using passive radiometric measurements on and near the 118.75 GHz O2 transition. Temperature profiles derived from this band complement those derived using the 50-60 GHz complex by providing independent measurements, albeit with reduced sensitivity at higher altitudes and less penetrability of clouds and precipitation. However, diffraction-limited apertures of fixed size will yield temperature profiles with better horizontal spatial resolution with 118 GHz measurements compared with data from 50-60 GHz. As a result, channels near 118 GHz are being considered for use in sonding and imaging from a geostationary microwave sensor. Moreover, the difference in response between similar clear-air channels at 50-60 GHz and ~118 GHz will provide additional information on cloud and precipitation amounts. 3.8.7 Precipitation Passive microwave measurements near 89 GHz play an important role in the retrieval of precipitation data, particularly over land. Owing to the combination of high emissivity and cloud thickness and temperature over land, signatures of convective precipitation cells are often strongest at 89 GHz. At this frequency there is high sensitivity to clouds over land, causing the upwelling brightness temperatures to be cooler rather than warmer, as observed over a relatively cold ocean background. Clouds over land exhibit much less contrast at lower microwave window frequencies (e.g., 10, 18, and 37 GHz) causing 8 GHz observations to play an important role in determining rain rate over land. See also §3.5.2.

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Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses 3.8.8 Cloud Base Height and Cloud Parameters A spaceborne 94 GHz cloud-profiling radar (CloudSat) was successfully launched in May 2006, with an objective of measuring the altitude and properties of clouds with 500 m vertical resolution, 1.2 km cross-track resolution, and with a sensitivity of −30 to −36 dBZ (decibels of Z, where Z is the energy reflected back to the radar, or reflectivity). This advanced W-band radar will gather information on the vertical structure of highly dynamic cloud systems to provide global measurements of cloud properties. These measurements will help scientists compile a database of cloud properties to improve the representation of clouds in global climate and numerical weather-prediction models. Cloud base information for a range of cloud types, particle distributions (microphysics), and liquid water content is desired to support both operational and scientific objectives. Ceiling height data are vital to identify regions of potential aircraft icing and for determining the most effective altitudes for commercial flight operations. For climate measurements, cloud base height is critical for determining the long-wave energy budget at Earth’s surface, and for understanding the impacts of anthropogenic aerosols on cloud formation, precipitation, and short- and long-wave energy fluxes. 3.8.9 Microwave Radiometric Imagery See §3.5.13 for applications of microwave radiometric imagery. 3.9 BANDS BETWEEN 126 AND 400 GHZ In addition to the bands listed in Table 3.8, the 130-134 GHz and 237.9-238 GHz (cloud radars only) are EESS active bands. The 155.5-158.5 GHz EESS passive band expires January 1, 2018. 3.9.1 Molecular Lines The atmospheric windows at 1 mm (200-300 GHz) and 0.8 mm (325-375 GHz) contain a wide range of interstellar molecules. The J = 3 → 2 and J = 4 → 3 transitions of such species as HCO+ and HCN are important tracers of high-density gas in the molecular clouds. The J = 2 → 1 and J = 3 → 2 lines of CO, as well as its isotopic variants, lie in these bands. Multiple transition studies of CO enable the density and temperature profiles of molecular clouds to be determined and are used as tracers of the total amount of molecular gas. Also in these wavelength regions, diatomic hydride and polyatomic hydride species have some of their lowest-energy rotational transitions, such as MgH, KH, H2O, and H3O+. In fact, only at frequencies above 200 GHz can these hydride molecules be studied in the interstellar medium. Because they contain hydrogen atoms bonded to one heavier atom, they rotate very quickly. Therefore, their rotational transitions lie at higher frequencies than those of other interstellar molecules. Investigating simple hydride species is crucial for interstellar chemistry. Because of the high abundance of hydrogen, such species are prevalent in molecular clouds and are the initial species produced by interstellar chemistry. Passive measurements near the 183.31 GHz water-vapor line, aided by measurements in the adjacent transmission window at the EESS-allocated bands of 150-151 GHz or 164-168 GHz, are critical for the global measurement of atmospheric water-vapor profiles. Measurements from spaceborne sensors in LEO are carried out to obtain atmospheric water-vapor profiles from Earth’s surface to 100 mb with a measurement uncertainty of ~20 percent and ~35 percent for clear and cloudy conditions, respectively. These measurements are used to support meteorological forecasting and climatological modeling. Mois-

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Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses TABLE 3.8 Frequency Allocations Between 126 and 400 GHz: Bands, Services, Footnotes, and Scientific Uses   Band (GHz) Services Footnotes Scientific Use 140.69-140.98 MS, MSS, RAS, RNS,RNS, rls 5.149,1 5.340,2 5.5553 H2 CO 144.68-147.12 RLS, aems, aemss, RAS4 5.149, 5.555 H2CO, DCN (Note: DCO+ at 144.07 GHz) 148.5-151.0 EESS (passive), RAS, SRS (passive) US246   150-151 EESS (passive), FS, FSS (S→ E), MS, SRS (passive), ras 5.149, 5.385,5 US2636 NO, H2 CO 151-156 FS, FSS (S→ E), MS US2117 CS, CH3CN, CH3CCH 156-158 EESS8 (passive), FS, FSS (S→ E), MS     158-164 FS, FSS (S→ E), MS US211   164-167 EESS (passive), RAS, SRS (passive) US246 (H2S at 168.7 GHz) 170-174.5 FS, ISS, MS, ras9 5.149, 5.385   174.8-182.0 EESS (passive), FS, ISS, MS, SRS (passive), ras10 5.149, 5.385, US263   176.5-182 FS, ISS, MS, ras11 5.149, 5.385, US211   182-185 EESS (passive), RAS, SRS (passive) 5.340,12 5.563,13 US24614   185-190 FS, ISS, MS, EESS (passive), ras15 5.149, 5.385, US211   190.0-191.8 EESS (passive), SRS (passive) 5.340, US246   200-209 EESS (passive), RAS, SRS (passive) 5.341,16 5.563A, US74, US246   209-217 FS, FSS (E→ S), MS, RAS 5.341, 5.342   217-226 FS, FSS (E→ S), MS, RAS, SRS (passive) 5.562B, 5.341, 5.342   226-231.5 EESS (passive), RAS, SRS (passive) US246   231.5-235 FS, FSS (S→ E), MS, rls US211 12CO 235-238 EESS (passive), FS, FSS (S→ E), MS, SRS (passive) US263   250-252 EESS (passive), SRS (passive), RAS17 5.149, 5.55518 NO 261-265 MS, MSS, RAS,19 RNS, RNSS 5.149, 5.385,20 5.554, 5.555, 5.56421 HCN, CCH 265-275 FS, FSS, MS, RAS 5.149 HCO+ 275-300 5.56524 N2H+

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Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses Band (GHz) Services Footnotes Scientific Use 300-400 (ras), (eess), (srs) 5.565 CO, CS, CN, HCO+, HCN, MgH, H3O+, SiO NOTE: For definitions of acronyms and abbreviations, see Appendix I. For information about other features of this table, see §3.1.2, “Note to the Reader Regarding Frequency Allocation Tables.” 15.149 urges protection of RAS. 25.340 forbids emissions from airborne stations and from space stations toward Earth between 140.69 and 140.98 GHz. 35.555 adds RAS as primary in the bands 140.69-140.98 GHz, 144.68-144.98 GHz, 145.45-145.75 GHz, and 146.82-147.12 GHz. 45.555 adds RAS as primary in the bands 140.69-140.98 GHz, 144.68-144.98 GHz, 145.45-145.75 GHz, and 146.82-147.12 GHz. 55.385 adds RAS as secondary in the bands 150-151 GHz, 174.42-175.02 GHz, 177-177.4 GHz, 178.2-178.6 GHz, 181-181.46 GHz, 186.2-186.6 GHz, and 257.5-258 GHz. 6US263 specifies that EESS and SRS will not be protected from FS and MS. 7US211 urges additional protection to RAS from adjacent bands. 8Except in the United States. 9In the sub-band 174.42-175.02 GHz. 10In the sub-band 174.42-175.02 GHz. 11In the sub-bands 177-177.4 GHz, 178.2-178.6 GHz, and 181-181.46 GHz. 125.340 forbids all emissions, but see 5.563. 135.563 adds FS and MS in the United Kingdom. 14US246 forbids all emissions. 15In the sub-band 186.12-186.6 GHz. 165.341 makes note of SETI observations in this band. 17In the sub-band 250-251 GHz. 185.555 adds RAS as primary for 250-251 GHz and 262.24-262.76 GHz. 19In the sub-band 262.24-262.76 GHz. 205.385 adds RAS as secondary for 257.5-258 GHz. 215.564 makes RAS primary within the larger band 252-265 GHz in Germany, Argentina, Spain, Finland, France, India, Italy, and The Netherlands. 22In the United States. 23In the United States. 245.565 urges that administrations take all practicable steps to protect the passive services from harmful interference in certain designated bands, and other bands yet to be identified, until the next competent World Radiocommunication Conference. ture profiles can also be used to support path delay and attenuation estimates for active remote sensing systems (e.g., radar altimetry) and satellite radio-frequency links. Accurate measurements of upper tropospheric water vapor are also obtained by viewing Earth’s limb from LEO to support scientific studies of the upper atmosphere and atmospheric chemistry. In general, measurements near 183 GHz are widely used. Observation from geostationary orbit is planned in the future. 3.9.2 Atmospheric Water-Vapor Profile The hydrologic cycle is critical to the dynamical and thermodynamical functioning of the global climate system and to its impacts on human society. The distributions of water vapor, cloud liquid water, and cloud ice in the atmosphere and the evolution of these distributions with time determine to a great extent the radiation characteristics of clouds, with consequent large impacts on the radiation balance of the atmosphere. Water vapor is an important greenhouse gas, greatly influencing the surface radiation budget even in the absence of clouds. Condensation and evaporation of water in the atmosphere affect large transfers of energy and have enormous influence on large-scale circulation in the troposphere.

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Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses Atmospheric profiles of moisture measured from polar-orbiting LEO satellites are required to initialize high-resolution global ocean-atmosphere models that provide the global meteorological and oceanographic predictions necessary for civil and military operations. Much of the atmospheric moisture is concentrated close to Earth’s surface in the lowest ~1.5-2.5 km of the atmosphere. Comparisons of model simulations indicate that if the measurement accuracies of moisture profiles are less than threshold values (generally those values listed above), the remotely sensed profile data that are used as input corrupt the model rather than increases its capability to forecast. Observational errors, usually on the smaller scales, amplify and, through nonlinear interactions, gradually spread to the longer scales, eventually destroying forecast skill. In previous studies, numerical models using data with a standard deviation of 0.5°C at all levels exhibited an exponential error growth with a doubling time of about 2.5 days. Similar results were found for other data types (i.e., winds, moisture, and so on) with forecast errors as high as 20 to 30 percent. Passive measurements near the strong 183.31 GHz water-vapor line, aided by measurements in the adjacent transmission window at the EESS-allocated bands of 150-151 GHz or 164-168 GHz, are critical for the global measurement of atmospheric water vapor profiles. Measurements from spaceborne sensors in LEO are carried out to obtain atmospheric water-vapor profiles from Earth’s surface to 100 mb with a measurement uncertainty of ~20 percent and ~35 percent for clear and cloudy conditions, respectively. These measurements are used to support meteorological forecasting and climatological modeling. Moisture profiles can also be used to support path delay and attenuation estimates for active remote sensing systems (e.g., radar altimeters) and satellite radio-frequency links. Accurate measurements of upper tropospheric water vapor are also obtained by viewing Earth’s limb from LEO to support scientific studies of the upper atmosphere and associated atmospheric chemistry. In general, water-vapor measurements near 183 GHz are widely used. 3.9.3 Precipitation Passive microwave remote sensing from satellites and aircraft at frequencies above 90 GHz are used to estimate hydrometeor properties of cirrus clouds and the higher altitude (frozen particle regimes) of convective and anvil clouds. Specific frequencies in use on various systems include 150 GHz, 166 GHz, 183.31± 1 GHz, 183.31± 3 GHz, 183.31±7 GHz, 183.31±10 GHz, 220 GHz, 325 GHz, 340 GHz, 380 GHz, 424 GHz, ~500 GHz, and 640 GHz. These channels are particularly sensitive to the frozen particles, and several have been used to estimate snowfall rate over land surfaces. Furthermore, since these channels tend to become opaque to the land surface in the presence of clouds, they may be useful in estimating light rain over land surfaces. Precipitation observation may be possible with high spatial resolution using a geostationary microwave sounder and frequencies at ~183, 340, 380, and 424 GHz. It is important to have knowledge of cirrus clouds and the frozen particles in convective and anvil clouds for several reasons: (1) in order to enhance cloud-resolving models, (2) to better understand the relationships between the frozen and melting particles, (3) to clarify relationships between the passive observations and frozen particles, (4) to improve latent heating and global change models that are particularly sensitive to cirrus ice clouds and to the ice in convective and anvil clouds, and (5) to provide indirect information on surface rain rate below the cirrus anvil. Finally, real-time estimates of snowfall rate would be extremely useful for urban management.

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Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses 3.9.4 Cloud Ice Water Path Retrieval of Cloud Ice Water Path (CIWP) data is supported by passive microwave measurements at 89 GHz and above (e.g., 150, 166, 183, ~220, and ~340 GHz). Retrieval of CIWP data depends strongly on knowledge of the cloud particle size distributions. Therefore, retrievals are improved using multiple high-frequency brightness temperature measurements. Measurement uncertainties of ~10 percent for the range of ~0.5-2.6 kg/m2 of CIWP are anticipated. The inclusion of cloud microphysics into cloud and climate models within the decade is anticipated by many numerical weather modelers. Accordingly, measurements of cloud ice water will be needed to diagnose and validate these cloud models, which, in principle, have the ability to greatly improve the understanding of climate, rainfall, and precipitation variability and the atmospheric radiation budget. 3.9.5 Atmospheric Chemistry The first Microwave Limb Sounder (MLS) on NASA’s Upper Atmosphere Research Satellite used channels near 63, 183, and 205 GHz to measure emissions of chlorine monoxide, water vapor, ozone, and sulfur dioxide. Chlorine monoxide is a key reactant in the chlorine chemical cycle that destroys ozone. A new MLS instrument is on NASA’s AURA spacecraft (launched in July 2004); it uses channels near 118 GHz for temperature and pressure profiling, 190 and 183 GHz for HNO3 and water-vapor measurements, 240 GHz for O3, and 640 GHz and 2.5 THz to support detailed studies of the stratosphere and the chemistry associated with ozone depletion. 3.9.6 Cosmic Background Radiation The frequency band at 217-231 GHz provides a continuum window near the peak of the 2.7 K cosmic background radiation. This radiation, emitted when the universe was only about 100,000 years old, is one of the most significant discoveries in the study of cosmology. Further detailed studies of its properties will yield unique information about the early universe. Observations of the cosmic background from the ground are severely limited by the high, variable intensity of atmospheric emission. Observations near this frequency are important for such fundamental measurement as the velocity of the Galaxy with respect to the background radiation field and the rotation and symmetry of the universe. Because of the low intensity of the background radiation, accurate measurement of its distribution must be made from high-altitude aircraft, balloons, and spacecraft in an environment free from interference.