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CHAPTER 4

Spectrum Availability

Introduction

National policies can address the problem of increased demand for spectrum in a number of ways. One way is to place greater reliance on market-based approaches (e.g., financial incentives to efficiency, flexibility, auctions, etc.) to guide spectrum management. NTIA in its NTIA Spectrum Policy Study and elsewhere has examined the use of market forces and recommended their greater use in many contexts. NTIA is mindful, however, that in some instances the use of such forces may not apportion spectrum between the public and private sectors in an economically efficient manner. While administrative processes have their own limitations, they may, in some instances, be superior to market forces in allocating spectrum for radio astronomy.

In the NTIA Requirements Study, an estimate of additional spectrum needed for the radio astronomy service was based on physical phenomena rather than expected service growth and effect of new technology. Radio astronomy does not actively transmit radio waves in the frequency bands allocated for its operation nor does it cause any harmful interference to other radio services. On the other hand, the received cosmic signals are extremely weak and transmissions from other radio services can interfere with reception and observations of such signals, so the protection of radio astronomy observations may preclude operation of active services in some cases. NTIA estimated the additional spectrum requirement for the radio astronomy service to be approximately 9.6 megahertz of additional allocations and access to an additional 231 megahertz by local coordination. Having identified the future spectrum requirements for the radio astronomy service, the next step in the NTIA strategic planning process is to identify the availability of spectrum that could satisfy those requirements.

This chapter will identify candidate spectrum to satisfy the shortfall for the radio astronomy bands identified in Chapter 3. NTIA believes that the spectrum and users near spectrum allocated for radio astronomy are sufficiently flexible to accommodate most, if not all, requirements for additional spectrum for the radio astronomy service. Note that the discussion contained herein is strictly for planning purposes and identifies possible long-range planning options to satisfy the additional radio astronomy spectrum requirements.

Long-Range Planning Options for Increased Spectrum Availability

When spectrum demands exceed available allocations, there is a limited number of long-range planning options possible to satisfy the demand for spectrum access. For the purposes of this study, four general long-range planning options are discussed in the following paragraphs along with their applicability to radio astronomy.

Option 1. Make More Efficient Use of Current Allocations. While most radio services can employ advanced spectrum-efficient technologies to increase communications capacity within allocated spectrum, other radio services such as radio astronomy are limited by the requirements for the observation of physical phenomenon in specific frequency bands and bandwidths. The block allocation system for the radio frequency spectrum has generally worked well since the 1920's. Recently, spectrum management has increased spectrum flexibility in many portions of the radio frequency bands by lessening arbitrary boundaries to accommodate other radio services employing advanced, spectrum-efficient technologies. Other approaches, such as employing geographical and topographic isolation of sensitive receivers, filtering of unwanted signals, time-sharing of bands between active and passive users, using specialized transmit and receive antennas, etc., can be employed to make current frequency allocations more accessible to other radio services and still offer protection to incumbent users. As was noted in an earlier NTIA study, new systems and services trying to gain access to certain portions of the radio frequency spectrum often must share with entrenched users with long histories of serving the public and private needs and who have large investments in equipment.(1) Increased sharing by geographical isolation is a viable approach for additional radio astronomy access.

Option 2. Reaccommodate Incumbent Spectrum Users. Under certain circumstances, it may be possible to reaccommodate spectrum users from one frequency band to another, or within the same frequency band, to clear the band or a portion of it for another active radio service. This was accomplished as a result of recent allocation decisions in which existing users were reaccommodated in other portions of the spectrum in favor of new radio services. One such example was the result of a recent World Radio Conference where existing HF users were reaccommodated in other portions of the HF spectrum in favor of new radio services. Another example here in the United States involves hundreds of microwave facilities that must be relocated to other frequency bands to accommodate the new personal communications services (PCS). Finally, recent legislation required the transfer of Federal Government allocated spectrum to the FCC.(2) The affected Federal systems will be reaccommodated within other portions of these bands, or to other frequency bands which have suitable and sufficient spectrum available. However, the accommodation of radio astronomy requirements should not require the relocation of any incumbent users.

Option 3. Use Other (non-spectrum) Technologies. The relative advantages of spectrum-dependent systems and wireline(3) systems are changing. Long-haul microwave systems are being converted to employ optical fiber cable to take advantage of fiber's higher communications capacity. The introduction of market-based approaches has the potential to drive users to switch between non-spectrum and spectrum-dependent technologies. However, there is no current substitute technology for the reception of cosmically-generated radio waves. Until lunar or space-based observations are established, Earth-based radio facilities must be employed.

Option 4. Use Higher Frequencies. Recent technological advances have made the spectrum above 20 GHz more usable for radio services. Extensive Federal Government research and development activities were responsible for developing radio applications for these bands primarily for space and military uses. However, much of this technology has been transferred to the private sector, encouraging the manufacturing of off-the-shelf components and systems that operate to 100 GHz. Although the radio astronomy community has identified some observations it needs at higher frequencies and has placed on the agenda of WRC-99 their spectrum requirements above 71 GHz, the lower frequencies will still be required.

Of the four long-range planning options discussed above, Option 1 appears the most feasible to satisfy radio astronomy spectrum requirements in the United States, although there may be some regulatory barriers. More spectrum can be made available by increasing the flexibility of allocation boundaries to increase use to other services. Sharing, in this sense, is possible among users or radio services by removing some “exclusive” designations of allocations to allow for shared use. Increased sharing among users or radio services can broaden radio service use and open up a separate or adjacent block(s) of spectrum. This is especially true when approaches such as geographical and topographic isolation of sensitive receivers, the filtering of unwanted signals, time-sharing of bands between active and passive users, and using specialized antennas can be employed to make current frequency allocations more accessible to other radio services

Coordination areas are established around various radio astronomy sites where frequency coordination procedures or allocation footnotes encourage a frequency applicant to minimize harmful interference to radio astronomy observations. For example, the NTIA Manual and the FCC Rules and Regulations specifically identify the coordination area at the National Radio Astronomy Observatory site at Green Bank, West Virginia as the area bounded by 39·15¢ N on the north, 78·30¢ W on the east, 37·30¢ N on the south, and 80·30¢ W on the west and require prior coordination (notification if non-Federal applicant) with the director of the observatory.(4) US Footnotes to the National Table of Frequency Allocations similarly identify other radio astronomy coordination areas. Some footnotes urge agencies to bear in mind that their operation may affect radio astronomy observations while other footnotes encourage agencies to take every practicable efforts to avoid the assignment of frequencies in the coordination areas specified.(5)

TABLE 4–1 below depicts the number of frequency assignments within the established coordination zones of major U.S. radio astronomy observatories in the requested frequency bands. Examining the spectrum environment at these bands of interest serves as a good gauge to see if those bands could serve as options to satisfy radio astronomy requirements. A listed frequency assignment does not indicate the number of transmitters—one assignment can have tens or hundreds of transmitters associated with it. Nonetheless, a count of assignments serves as a relative baseline for evaluation in a particular band. In locating spectrum available for the radio astronomy spectrum requirements, the table below was used to examine spectrum identified or required by radio astronomers. In identifying planning options for the radio astronomy service, NTIA was mindful that the criteria used should: (1) allow for a reasonable inclusion of the radio astronomy service; (2) the option(s) selected would have minimum number of frequency assignments or licenses; and (3) that primary users would probably be amenable to allowing the radio astronomy service access to the bands. No attempt was made to determine real-time spectrum occupancy of these assignments.

TABLE 4–1.
Spectrum Environment Within Radio Astronomy Coordination Zones
(Federal/non-Federal Assignments)
Frequency
Bands (MHz)
Radio Astronomy Observatories
Arecibo, PR Green Bank, WV Socorro, NM Owens Valley, CA
« 150.05–153 13/942 0/236 20/307 0/58
« 322–328.6 7/0 0/0 5/0 0/0
† 13.36–13.41 1/1 0/0 0/0 0/0
†† 13.276–13.410 2/1 0/0 3/0 0/0
† 25.55–25.67 0/0 0/0 1/0 0/0
†† 25.414–25.67 11/0 2/0 2/0 0/0
† 406.1–410 22/0 7/0 98/0 6/0
†† 406–410.1 30/0 28/0 103/0 7/0
† 608–614 1/1 0/2 0/0 0/0
†† 607.95–614.05 1/1 0/2 0/0 0/0
† 2690–2700 0/0 0/0 1/0 0/0
†† 2673–2700 0/0 0/0 1/0 0/1
† 4990–5000 0/0 0/0 0/0 0/0
†† 4950–5000 1/0 0/0 0/0 0/0
† 10600–10700 0/62 0/1 0/2 0/0
†† 10593–10700 0/62 0/1 0/2 0/0
† 15350–15400 0/0 0/0 0/0 0/0
†† 15256–15400 2/0 1/0 0/0 0/0
· 1370–1400 0/0 0/0 5/0 0/0
· 1606.8–1610.6 0/0 0/0 0/0 0/0
· 1659.8–1660 0/0 0/0 0/0 0/0
· 1714.8–1722.2 2/0 3/0 13/0 1/0
· 4813.6–4834.5 0/0 0/0 5/0 0/0
Notes:
« New allocation requested in this band.
† Radio astronomy allocated band requiring additional access.
†† 1% increase of bandwidth to radio astronomy band to provide for additional access.
· Access required for spectral-line observations.

Spectrum Availability for Radio Astronomy Continuum Observations

The NTIA Requirements Study listed an additional 9.6 megahertz requested for radio astronomy continuum observations. The two frequency bands discussed below were identified by NSF as candidates to satisfy the radio astronomy requirement for protected frequencies for observations between 74.6 MHz and 406.1 MHz. A change in the National Table of Frequency Allocations would be necessary to provide radio astronomy co-primary status with existing primary radio services. These changes could be in the form of a direct table listing or by footnote indicating primary allocation to the radio astronomy service, in limited areas.

150.05 – 153 MHz. Although the NSF has indicated this band as one of two bands for new allocations in support of continuum observations, this band presently has large numbers of incumbent users. In this band, the radio astronomy service would likely have to coordinate with 33 Federal Government fixed and mobile users and approximately 1543 non-Federal users in the coordination zone to permit successful observations. The table below reflects the number of assignments/licenses in each of the coordination zones for the listed radio astronomy observatory.

TABLE 4-2.
Frequency Assignments in the Radio Astronomy Coordination Zones (150.05 - 153 MHz)
Radio Observatory Federal Non-Federal
Arecibo, PR 13 942
Green Bank, WV 0 236
Socorro, NM 20 307
Owens Valley, CA 0 58

322 – 328.6 MHz. The 322–328.6 MHz band in which radio astronomy is also seeking allocation is presently allocated to the Federal Government for fixed and mobile services. Nationwide, approximately 672 Federal fixed and mobile government assignments are in this band, and though the total number of assignments in this band appears large, there are only two radio observatories that have assignments in their coordination zones: Arecibo, Puerto Rico (7) and Socorro, New Mexico (5). It should be noted that this band has a primary radio astronomy allocation internationally, and Footnote 644 in the National Table of Frequency Allocations, urging administrations to take all practicable steps to protect radio astronomy, applies to the United States.(6)

Spectrum Availability for Radio Astronomy Increased Bandwidth and Spectral–Line Observations

In addition to the 9.6 megahertz of new allocations, the NTIA Requirements Study also noted that shared access to an additional 231 megahertz by local coordination was needed for increased bandwidth to radio astronomy allocations not having minimum bandwidths and access to additional spectrum for spectral-line observations. The increased bandwidth is required to meet the one percent bandwidth required for radio astronomy observations in the band of interest. Radio astronomy access to bands below could be by footnote to the National Table of Frequency Allocations with language similar to some of the existing footnotes noting radio astronomy needs and operations.(7) For example, Footnote US256 reads:

Radio astronomy observations may be made in the band 1718.8–1722.2 MHz on an unprotected basis. Agencies providing other services in this band in the geographic areas listed below should bear in mind that their operation may affect those observations, and those agencies are encouraged to minimize potential interference to the observations insofar as it is practicable.(8)

Increased Bandwidth Requirements

13.36 – 13.41 MHz and 25.55 – 25.67 MHz. In the 13.36–13.41 MHz radio astronomy band, the radio astronomy service is seeking access to an additional 84 kHz. The HF spectrum just below this band is allocated to the aeronautical mobile (R) service(9) and the spectrum above the band is allocated to the fixed service. As a general rule, HF frequencies are not used for aeronautical mobile (R) communications when aircraft are within the airspace of the conterminous United States.(10) This is evident from the small number of assignments in this band. Access to the additional 84 kHz could be provided in the frequency band 13.31–13.444 MHz by sharing 50 kHz in the aeronautical mobile (R) band below and 34 kHz in the fixed service band above.

The 25.55–25.67 MHz band is allocated for the radio astronomy service and has fixed and mobile allocated bands just below it with the broadcasting service allocation just above. An increase to one percent results in 136 kHz of additional spectrum in this band. Access by footnote to the fixed and mobile band appears more feasible than to the broadcast band due to the small number of assignments therein. The increased requirement could be satisfied by radio astronomy access to 25.414–25.67 MHz.

406.1 – 410 MHz and 608 – 614 MHz. Additional bandwidth increase to one percent is also sought for the radio astronomy bands 406.1–410 MHz and 608–614 MHz in support for continuum observations. Approximately 200 kHz would be required to increase the bandwidth to one percent for the 406.1–410 MHz band. The band below is allocated to the mobile-satellite (Earth-to-space) service and the band above is allocated to the fixed and mobile services. Access by footnote to 100 kHz looks feasible at 406–406.1 MHz where the radio astronomy and mobile-satellite (Earth-to-space) services should make ideal sharing partners.(11) Access to an additional 100 kHz in the heavily-used Federal mobile band would be difficult.

In the 608–614 MHz band, an additional 100 kHz is needed to increase the bandwidth to one percent. This radio astronomy band is sandwiched between two broadcasting allocations. Access to the additional spectrum by footnote to the band 607.95–614.05 MHz appears feasible; however, radio astronomy coordination and protection could be limited.

2690 – 2700 MHz and 4990 – 5000 MHz. In the 2 GHz and 5 GHz ranges, the radio astronomy service also requested a one percent bandwidth in the 2690–2700 MHz and 4990–5000 MHz allocated bands. The band 2690–2700 MHz has broadcast satellite and fixed allocations just below it; while aeronautical radionavigation and meteorological aids services are just above it. A one percent access in the 2690–2700 MHz band requires approximately 17 megahertz more spectrum. This requirement could be satisfied with a partial modification to Footnote 269 (e.g., applicants to space stations assignments are urged to take all practical steps to protect radio astronomy observations in the adjacent band 2673–2700 MHz from harmful interference).

For the 4990–5000 MHz radio astronomy allocation, a 40 megahertz increase is needed. Neighboring allocations just below it are the fixed and mobile services; while above it is the aeronautical radionavigation service. Because of the small number of assignments around the radio observatories, it appears 4950–4990 MHz is more likely to support the increased bandwidth requirement by footnote than 5000–5040 MHz.

10.6–10.7 GHz and 15.35–15.4 GHz. At the 10.6–10.7 GHz and 15.35–15.4 GHz radio astronomy bands, an increase of 7 megahertz and 104 megahertz in the bandwidths, respectively, would satisfy the one percent need for increased bandwidth for continuum observations. Fixed service allocations for non-Federal Government use is the allocation just below the 10.6–10.7 GHz band, whereas the fixed and fixed-satellite services are allocated just above it. Since there is no increase in the number of assignments in the radio astronomy coordination zones in the 10.593–10.6 GHz band nor is there an appreciable increase in the total number of U.S. assignments, access by footnote to the lower band (10.593–10.6 GHz) looks more feasible to satisfy the requirement with access to the band 10.593–10.7 GHz.

In the 15.350–15.4 GHz band, the fixed service allocation for government use is the allocation just below it and aeronautical radionavigation service allocation just above it. It appears more feasible to satisfy the radio astronomy requirement at 15.256–15.4 GHz by footnote than to increase by one percent in the 15.350–15.4 GHz band given the almost negligible increase of assignments around the radio astronomy observatories.

Access to Spectrum for Additional Spectral-Line Observations

Radio astronomers have identified approximately 1000 spectral lines. The IAU maintains a list of the frequencies it considers most important for spectral-line observations.(12) The frequency bands listed below are those identified by the NSF as necessary to extend protection of the most important spectral lines to more highly redshifted (lower) frequencies or to afford protection to important spectral lines that are not currently within a band allocated exclusively to the passive services.(13) The total additional spectrum access requested in these bands is 62.3 megahertz.

1370 – 1400 MHz. Radio astronomers are seeking access to 30 MHz in the 1370–1400 MHz band, presently allocated to the Federal Government for fixed, mobile, and radiolocation services. This band is heavily used for various military radiolocation purposes for high-power, long-range surveillance radars. Also, the Department of Defense (DOD) and the Federal Aviation Administration (FAA) have implemented a joint program to field modernized air route surveillance radars for air defense, drug interdiction, and air traffic control. Since the fixed and mobile services were upgraded to primary status in 1989, this band has seen increased use for fixed links and mobile links. At national and military test ranges, the DOD employs this band for drone telecommand. NTIA plans to reallocate the 1385–1400 MHz portion of this band for non-Federal use after January 1999.(14) It appears possible that some access by the radio astronomy service could be granted via a footnote stipulating coordination requirements.

1606.8 – 1610.6 MHz. Additional access is also sought by radio astronomers in the 1606.8–1610.6 MHz range. The 1559–1610 MHz band is presently allocated in the United States to the aeronautical radionavigation and radiodetermination satellite (space-to-Earth) services. In this band, the Global Positioning System (GPS) operates on a center frequency of 1575.42 MHz and is part of the radionavigation satellite service.(15) Federal and private sector use of the GPS is extensive. It includes radionavigation (land, sea, and air), surveying, aircraft landing aids, position location, traffic management, and scientific research. Radio astronomers have long identified satellite systems as interfering sources to their observations.(16) It appears doubtful that radio astronomy could avoid interference in this band. The band 1610–1610.6 MHz is allocated to the aeronautical radionavigation, radiodetermination satellite, and mobile-satellite service (Earth-to-space). Limited access to this band may be possible since sharing with satellite uplinks is feasible.

1659.8 – 1660 MHz.Access is sought by radio astronomers to the 1659.8–1660 MHz portion of the 1651–1660 MHz band where U.S. allocations are for the aeronautical mobile-satellite and mobile-satellite services. The American Mobile Satellite Corporation uses this band for the uplink of their nationwide mobile satellite system. Access to this band could be by footnote and would probably be contingent on a mutually agreeable coordination arrangement between these mobile satellite users and the radio astronomers to minimize or eliminate interference from mobile satellite systems operating in this band.

1714.8 – 1722.2 MHz. Access to the 1714.8–1722.2 MHz band is also sought by the radio astronomers for spectral-line observations to enhance observations of the redshifted spectral line of the hydroxyl radical, essential for understanding interstellar medium and star formation in other galaxies. This band is a portion of the 1710–1850 MHz band that, in the United States, is presently allocated to the fixed and mobile services and by footnote to the space operation service at 1761–1842 MHz. While the 1710–1850 MHz band is the predominant medium-capacity, point-to-point fixed service band for links operated by Federal agencies, NTIA will reallocate the 1710–1755 MHz portion of this band for non-Federal use after January 2004.(17) Access to the 1714.8–1722.2 MHz band by footnote appears feasible noting its low usage around radio astronomy observatories.

4813.6 – 4834.5 MHz. The band 4800–4990 MHz is presently allocated in the United States for fixed and mobile use for Federal Government agencies and is heavily used by the military services for tactical communications, both line-of-sight and troposcatter applications. Other usage of this band by the military services includes extensive transportable fixed use, DOD air-to-ground data links, drone command and controls systems, air defense, and many other systems. Any access by footnote, if at all, by the radio astronomers to the 4813.6–4834.5 MHz band will require extensive coordination arrangements.

Summary of Long-Range Planning Options

For the purposes of spectrum planning, the following frequency bands could be considered as planning options for satisfying future radio astronomy spectrum requirements as identified in the NTIA Requirements Study. While identifying planning options for the radio astronomy service, NTIA was mindful that the criteria should be: (1) the inclusion of the radio astronomy service is reasonable; (2) the options selected would have minimum impact on current users, primary users would probably be amenable to allowing the radio astronomy service access to the bands; and, (3) the public benefits of additional scientific observations would outweigh potential benefits from the use of these frequencies for other services.

Spectrum Availability and Planning Options

Purpose Candidate Frequency Band Additional Spectrum Requirement Incumbent Radio Service(s) Approx. Number of Assignments Within Coordination Zones
Federal/non-Federal
Share Allocation 150.05-153 MHz 2.95 MHz Fixed, Mobile 33/1543
322-328.6 MHz 6.6 MHz Fixed , Mobile 12/0
Increase access for Continuum Observations From 13.36-13.41 MHz to 13.310-13.444 MHz 84 kHz -- Increases allocation to 1 % Aeronautical Mobile (R), Fixed 5/1
From 25.55-25.67 MHz to 25.414-25.67 MHz 136 kHz -- Increases allocation to 1 % Fixed, Mobile 15/0
From 406.1-410 MHz to 406-410.1 MHz 200 kHz -- Increases allocation to 1 % Mobile Satellite (Earth-to-space), Fixed, Mobile 168/0
From 608-614 MHz to 607.95-614.05 MHz 100 kHz -- Increases allocation to 1 % Broadcasting 1/3
From 2690-2700 MHz to 2673-2700 17 MHz -- Increases allocation to 1 % Broadcast Satellite, Fixed 1/1
From 4990-5000 MHz to 4950-5000 MHz 40 MHz -- Increases allocation to 1 % Fixed, Mobile 1/0
From 10.6-10.7 GHz to 10.593-10.7 GHz 7 MHz -- Increases allocation to 1 % Fixed 0/65
From 15.35-15.4 GHz to 15.256-15.4 GHz 104 MHz -- Increases allocation to 1 % Fixed 3/0
Increase access for Spectral-Line Observations 1370-1400 MHz 30 MHz Fixed, Mobile, Radiolocation 5/0
1606.8-1610.6 MHz 3.8 MHz Aeronautical Radionavigation, Radiodetermination Satellite, Mobile-Satellite 0/0
1659.8-1660 MHz 200 kHz Aeronautical Mobile Satellite, Mobile Satellite 0/0
1714.8-1722.2 MHz 7.4 MHz Fixed, Mobile, Space Operation 19/0
4813.6-4834.5 MHz 20.9 MHz Fixed, Mobile 5/0

Endnotes

(1) See HF Report, supra note <4>, at 2–1.

(2) Omnibus Budget and Reconciliation Act, Title VI, § 6001(a)(3), Pub. L. No. 103–66, 107 Stat. 379, (Aug. 10, 1993) (codified at 47 U.S.C. § 921 et seq.)

(3) In this discussion, the term "wireline" is applied to systems that use electromagnetic transmissions, but are inter-connected by wire, fiber optic cable, or other non-radiating media.

(4) NTIA Manual, supra note <10> §8.3.9 at 8–41 and Telecommunications, 47 C.F.R. §5.69 at 592 (1996). See also Footnote US117, NTIA Manual, supra note <10> §4.1.3, at 4–103.

(5) See Footnotes US203, US256, US257, and US311, NTIA Manual, supra note <10> §4.1.3, at 4–104, 4–108, 4–108, and 4–112, respectively.

(6) See Footnote 644 in the 322–328.6 MHz band entry to the Tables of Frequency Allocations for both the International and United States allocations, NTIA Manual, supra note <10> §4.1.3, at 4–48.

(7) See Footnotes US203, US256, and US269, NTIA Manual, supra note <10> §4.1.3, at 4–104, 4–108, and 4–109, respectively.

(8) See Footnote US256, NTIA Manual, supra note <10> §4.1.3, at 4–108.

(9) The aeronautical mobile (R) service is intended for communications with aircraft or between aircraft relating to safety and regularity of flight, primarily along national or international civil air routes. See HF Report, supra note <4>, at 3–7.

(10) The need to use HF was eliminated through successful implementation of very high frequency (VHF) air traffic control communications. See HF Report, supra note <4>, at 3–7.

(11) It was pointed out by U.S. Department of Commerce National Oceanic and Atmospheric Administration (NOAA) that an ideal sharing partnership should exist between the radio astronomy service and mobile satellite (Earth-to-space) service in the 406–406.1 MHz band. Being a passive radio service, the radio astronomy service would not cause radio frequency interference to search and rescue satellite-aided tracking (SARSAT) satellites and SARSAT low-power emergency position indicating radiobeacons (EPIRBs), when activated, would unlikely cause any interference to radio astronomy observations. In the event that a SARSAT EPIRB was activated near a radio astronomy observatory, radio astronomy observations would have to accommodate since SARSAT is a safety-of-life system. See electronic mail from Richard Barth/NOAA to Joseph Camacho/NTIA, Sep 27, 1997, subject: Radio Astronomy Spectrum Planning: IRAC Doc 30341/1 (on file at NTIA).

(12) See NSF Comments, supra note <26> at 17–18, Sep 30, 1992. The list is included in Recommendation 314 of the ITU Recommunication Sector 1994 RA Series.

(13) Id.

(14) National Telecommunications and Information Administration, U.S. Department of Commerce, NTIA Special Publication 95–32, Spectrum Reallocation Final Report, at Table 5–1(1995) and NTIA Special Publication 98-36, Spectrum Reallocation Study as Required by the Balanced Budget Act of 1997, (1998).

(15) The GPS is a multi-satellite system with large numbers of U.S. and international users. The International Civil Aviation Organization (ICAO) has recognized the GPS and Global Navigation Satellite System (GLONASS–a Russian Federation System) as the two principal candidates for the Global Navigation Satellite System. See National Telecommunications and Information Administration, U.S. Department of Commerce, Spectrum Use Summary: 137 MHz – 5 GHz, at 11 (1559–1610 MHz entry) (Jul 15, 1996).

(16) Currently, the Global Navigation Satellite System (GLONASS) is causing interference to radio astronomy observations. It is anticipated that the GLONASS frequencies will be changed to a lower frequency.

(17) Applications include law enforcement networks and control links for various power, land, water, and electric-power management systems. Specific agency applications for fixed links include the FAA remote data transmission of critical flight safety data in support of essential aeronautical services, Army tactical radio relay systems, Departments of Agriculture and Interior backbone links for control of land mobile radio systems necessary for fire fighting, law enforcement, and disaster control with national forests and for provision of voice and data connections between sites where commercial service is not available, and Departments of Treasury and Justice microwave links related to law enforcement and public safety. NTIA will reallocate the 1710–1755 MHz portion of this band for non-Federal use after January 2004, under conditions that will permit some Federal systems to continue to operate. Id., at 11 (1710–1850 MHz entry).

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