RADIO ASTRONOMY
SPECTRUM PLANNING OPTIONS

U.S. DEPARTMENT OF COMMERCE
National Telecommunications and Information Administration

NTIA Special Publication 98–35

U.S. Department of Commerce

Larry Irving, Assistant Secretary for Communications and Information,
and Administrator, National Telecommunications and Information Administration

April 1998

    Executive Summary					ix
    
    Foreword						xiii
    
    CHAPTER 1:
    Radio Astronomy and the Electromagnetic Spectrum	1-1
    Introduction					1-1
    Radio Astronomy Service				1-1
    National Asset					1-2
    Synergism with Other Sciences			1-2
    Modern Radio Astronomy				1-6
    Radio Astronomy Frequency Allocations		1-6
    Cosmic Radio Sources				1-10
    Electromagnetic Spectrum				1-11
    Radio Astronomy Observatories			1-12
    Other Radio Astronomy Benefits			1-13
    
    CHAPTER 2:
    Radio Astronomy and Spectrum Management		2-1
    Introduction					2-1
    Protection in Frequency Bands Shared with
      Other Radio Services				2-1
    Protection from Transmitters in Adjacent Bands	2-2
    Sharing in Radio Astronomy Bands Below 40 GHz	2-3
    Increased Sharing					2-9

    CHAPTER 3:
    Radio Astronomy Spectrum Requirements		3-1
    National Spectrum Requirements			3-1
    Radio Astronomy Spectrum Requirements		3-1
    
    CHAPTER 4:
    Spectrum Availability				4-1
    Introduction					4-1
    Long-Range Planning Options for
      Increased Spectrum Availability			4-2
    Spectrum Availability for
      Radio Astronomy Continuum Observations		4-6
    Spectrum Availability for
      Radio Astronomy Increased Bandwidth
      and Spectral–Line Observations			4-7

    APPENDICES
    APPENDIX A: World Radio Astronomy Observatories	A-1
    APPENDIX B: Applications of Astronomical
      Techniques					B-1
    APPENDIX C: Preferred Frequency Bands for
      Radio Astronomical Measurements			C-1
    APPENDIX D: List of Acronyms and Abbreviations	D-1

The availability of the radio spectrum in the United States is critical to over 40 radio services that provide functions ranging from air traffic control, satellite communications, amateur radio operations, to radio astronomy. Although the radio frequency spectrum is not a consumable resource, the use of a frequency at a given location usually prevents that frequency from being used by others in the same geographic area. This need for exclusive geographic use to preclude harmful interference has led to current spectrum regulations that establish exclusive use of the spectrum by granting licenses for spectrum use, and the partitioning of the spectrum for shared use between radio services.

The National Telecommunications and Information Administration (NTIA), under a mandate from Congress to develop long-range spectrum plans, initiated the Strategic Spectrum Planning Program. As part of this long-term planning effort, NTIA released its NTIA Requirements Study ( U.S. National Spectrum Requirements: Projections and Trends) in March 1995 addressing all radio services, and found that eight of these services needed access to additional spectrum in order to satisfy user requirements to the year 2004.

While all radio services are important to the nation, one of the very important needs for spectrum is to support scientific research in the field of astronomy. Radio astronomy is a passive radio service that detects very faint radio emissions from cosmic sources. From its observations and studies of these radio emissions, the radio astronomy community has contributed much to humankind's knowledge of stellar physics, star formation, the interstellar medium, and the evolution of the Galaxy. They have also benefitted the public as a result of its many scientific discoveries and development of innovative technologies.

Recent national policies have placed greater reliance on market-based approaches to guide spectrum management. NTIA in its NTIA Spectrum Policy Study (U.S. Spectrum Management Policy: Agenda for the Future) 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. This report therefore uses the traditional, administrative long-range planning approach to address the spectrum needs for radio astronomy.

This report examines the additional radio astronomy spectrum requirements previously identified by NTIA. This report examines four general long-range planning options for increasing spectrum availability and identifies a number of frequency bands that could satisfy the radio astronomy spectrum requirements.

Radio Astronomy Usage

Radio astronomy is a relatively new radio service based on the reception of radio waves of cosmic origin through the use of radio telescopes. Unlike other radio services with which it shares the radio frequency spectrum, radio astronomy is a passive radio service and deals only with the reception of radio waves—cosmic radio waves. The radio astronomy community not only makes observations and conducts research in the radio frequency spectrum but in other portions of the electromagnetic spectrum as well. The study of the very faint radio emissions it receives have helped humankind's knowledge of stellar physics, star formation, the interstellar medium, the evolution of the Galaxy and the universe. The contributions and innovations developed by radio astronomy research have benefitted the public in many areas such as telecommunications, medicine, and industry, and it is very likely that radio astronomy will continue to benefit the public. Both NTIA and the Federal Communications Commission (FCC) recognize that the public interest can be served by providing for the radio astronomy service.

Spectrum Management and Radio Astronomy

The recognition of radio astronomy as a radio service similar in stature to broadcasting or mobile radio communications was an historic step since it provided a legal basis for radio astronomy to seek protection against any “harmful” interference. In the U.S. National Table of Frequency Allocations, the radio astronomy service has primary and secondary allocation status by both footnote and direct table listing. Many of the allocations to the radio astronomy service are shared allocations. Thus, being a passive radio service, the radio astronomy service is particularly vulnerable to interference whether it be from in-band, adjacent band, or spurious emissions. Coordination arrangements around major radio astronomy sites, delineated by established coordination zones, enhance the sharing of the spectrum involving geographical or time-sharing solutions. Because of the wide-ranging studies radio astronomers can perform, both NTIA and the FCC should encourage increased sharing between the radio astronomy service in frequency bands allocated to other radio services. Furthermore, NTIA and the FCC should consider the requirements of the radio astronomy service, when radio frequency bands at or near the preferred radio astronomy bands are reallocated, for the feasibility of sharing with the radio astronomy service.

Radio Astronomy Spectrum Requirements

The NTIA Requirements Study found that the total additional spectrum requirement for the radio astronomy service below 70 GHz is about 241 megahertz: 9.6 megahertz of additional allocations and access to an additional 231 megahertz by local coordination. Spectrum requirements for the radio astronomy service are somewhat different from those of most other radio services in that they are not dictated by predicted traffic requirements and, in the case of spectral lines, involve very specific frequencies. Allocations to satisfy radio astronomy requirements above 71 GHz have been placed on the agenda of 1999 World Radiocommunication Conference.

Long-Range Planning Options

When demands in the radio frequency spectrum exceed available allocations, there is a limited set of long-range planning options possible to satisfy the demand for spectrum access. For the purposes of this study, four long-range planning options for additional spectrum access were addressed. These options were: (1) make more efficient use of current frequency allocations; (2) reaccommodate incumbent spectrum users to other frequency bands; (3) use non-spectrum technologies such as fiber optic cable instead of radio spectrum; and (4) utilize higher frequencies.

Generally, long-range planning options for radio astronomy were limited to increased sharing in those bands of interest to the radio astronomy service. With respect to spectrum that could be made available for allocation to the radio astronomy service, the primary focus was on those frequency bands requested for new allocations, and for the expansion of existing allocations to one percent bandwidth of current frequencies.

For the purposes of long-range spectrum planning, the frequency bands outlined below could be considered for satisfying future radio astronomy spectrum requirements. Those bands for shared allocations are frequency bands of interest to radio astronomy and the bands for increased access are expansion of existing allocations to the minimum one percent bandwidth needed for adequate observations and research and for spectral-line observations.

Foreword

Background

The National Telecommunications and Information Administration (NTIA) is the Executive Branch agency principally responsible for developing and articulating domestic and international telecommunications policy. NTIA acts as the principal adviser to the President on telecommunications policies pertaining to the Nation's economic and technological advancement and to the regulation of the telecommunications industry. Accordingly, NTIA conducts studies and makes recommendations regarding telecommunications policies and presents Executive Branch views on telecommunications matters to the Congress, the Federal Communications Commission (FCC), and the public. NTIA is responsible for managing the Federal Government's use of the radio frequency spectrum. Management of the spectrum for the private sector, including state and local governments, is the responsibility of the FCC.

The NTIA report U.S. Spectrum Management Policy: Agenda for the Future (hereinafter NTIA Spectrum Policy Study),(1) published in 1991, recommended that NTIA and the FCC undertake a long-range spectrum planning effort that would forecast spectrum usage up to 15 years into the future. NTIA implemented this recommendation in the form of a Fiscal Year 1992 budget initiative for strategic spectrum planning. In appropriating funds for this effort, Congress tasked NTIA to provide strategic national spectrum planning to promote the effective and efficient use of the spectrum so that both near-term and long-term spectrum needs of the Federal Government and the private sector can be met. Strategic spectrum planning, in this context, involves (1) identifying a limited number of spectrum-use issues that require the attention of national-level spectrum-use regulators, and (2) developing a spectrum plan for implementation.

NTIA initiated the Strategic Spectrum Planning Program in response to this mandate from Congress to develop long-range spectrum plans. The program consists of three phases: (I) definition of long-term spectrum requirements, (II) development of spectrum availability and long-range planning options, and (III) development of spectrum allocation implementation plans. In March 1995, NTIA released a report entitled U.S. National Spectrum Requirements: Projections and Trends(2) (hereinafter NTIA Requirements Study). The NTIA Requirements Study marked the completion of Phase I of the NTIA Strategic Spectrum Planning effort. The NTIA Requirements Study addressed 40 radio services, limiting the spectrum forecast to a 10-year period. This study concluded that eight of these services needed access to additional spectrum in order to satisfy user requirements to the year 2004.

In October 1995, NTIA released the report Land Mobile Spectrum Planning Options,(3) the first in a series of reports that constitute Phase II of the spectrum planning effort addressing spectrum availability and long-range planning options. That report identified potential candidate frequency bands needed to satisfy the 204 MHz of spectrum shortfall identified in the NTIA Requirements Study. In November 1996, NTIA released the second report of Phase II, High Frequency (3–30 MHz) Spectrum Planning Options.(4) That report addressed the spectrum availability and long-range planning options for those services in need of additional high frequency (HF) spectrum as identified in the NTIA Requirements Study: mobile service, aeronautical mobile services, maritime mobile service, broadcasting service, and amateur services.(5)

The Need for Long-range Spectrum Planning

Long-range spectrum planning is critical to the effective management of the radio frequency spectrum. First, planning provides for the efficient development of spectrum-dependent telecommunications services. Before a service provider can offer the services, a license or authorization must be granted for the radiocommunications system. This system should operate in a frequency band that supports its function, and be relatively clear of potentially interfering stations. Forecasting the demand for these services, and allocating adequate spectrum for the radio service in advance will assure that the telecommunications services are provided in a timely and efficient manner.

Second, early identification of spectrum for an intended use gives manufacturers adequate lead time to design and manufacture equipment for the planned frequency bands. In the Federal Government, funds for new radiocommunications equipment must be programmed two to three years in advance to correspond with government budget cycles. Failure to plan spectrum for new systems could lead to delays in deployment, and inefficient use of taxpayers' money.

Effective long-range spectrum planning helps ensure that spectrum-dependent telecommunications remain one of today's prime “leverage technologies.” Throughout the Federal Government, the private sector, and state and local governments, the United States has relied on this technology to boost productivity, create jobs and investment opportunities, and improve services.

Advanced technologies have also allowed radio operation at higher frequencies, spawning new radiocommunications services. Further, consumers are demanding additional spectrum-dependent services at an ever-increasing rate, to the degree that there is no longer a firm correlation between future spectrum requirements and many current spectrum allocations. As an example, some mobile systems are capable of operating in portions of the spectrum once the sole domain of fixed microwave systems. Failure to plan adequately for future radio system usage has resulted in a mismatch between demand for services and the availability of appropriately allocated spectrum.

Effects of National and International Planning Policies on Spectrum Availability

Under current regulations, spectrum used by licensed or unlicensed user devices is first allocated for a particular use. These regulations are either the FCC's regulations contained in Title 47 of the Code of Federal Regulations, or the regulations governing Federal use of the spectrum contained in the Manual of Regulations and Procedures for Federal Radio Frequency Management (NTIA Manual). At the present time, the radio frequency spectrum in the United States from 9 kHz to 300 GHz is completely allocated to one or more radio services.

As a basic plan for usage, the radio spectrum is allocated to various radio services in blocks of frequencies. The concept of the block allocation system provides for a band of contiguous frequencies dedicated to one or more radio services, depending on the technical and operational characteristics of the service(s). A block so dedicated is said to be allocated to the radio service(s) associated with that block. Further, within a block, the radio services may have a hierarchical structure (primary or secondary) that grants rights or imposes limitations on the services relative to other services in the same block. Within the United States, the compilation of these spectrum blocks, along with associated footnotes, is called the National Table of Frequency Allocations,(6) and is used for general spectrum planning. The table also further separates those allocation blocks that are managed by NTIA from those managed by the FCC.(7) For the allocation of frequencies internationally, the world has been divided into three regions as contained in the International Telecommunication Union (ITU) Table of Frequency Allocations of Article 8 of the ITU Radio Regulations. The United States is within Region 2 as shown in the figure below.

Chart of ITU Regions

There is, however, considerable flexibility in the block allocation system. Footnotes to the allocation blocks may permit operation of additional radio services in the spectrum block, restrict the operation of services allocated in the block, specify or clarify the relative status of services in a block, or stipulate other requirements for operation. Other footnotes may permit multi-mode operation, where the transmitted signal is used for more than one purpose, and would otherwise be separate radio services.

To comply with treaty obligations, radio systems are generally permitted to use only spectrum that is allocated to the radio service associated with that system. Revisions to the international allocation table resulted from decisions at ITU World Radiocommunication Conferences (WRC's, previously known as World Administrative Radio Conferences: WARC's). ITU conferences have been held periodically since 1947, with major allocation conferences (General WARC) held in 1959 and 1979 (WARC–59 and WARC–79) and the most recent WRC having been convened in 1997. Since WARC–79, ITU conferences have addressed only selected bands for reallocation. Consequently, many decisions of past conferences remain in force.(8) WARC's with limited agendas considered space and radio astronomy matters in 1963, 1971, and 1977; aeronautical mobile (R) matters in 1966 and 1978; HF broadcasting in 1984 and 1987 (HFBC–84 and HFBC–87); maritime mobile matters in 1967 and 1974; mobile matters in 1983 and 1987 (MOB–83 and MOB–87); space matters in 1985 and 1988 (ORB–85 and ORB–88); and mobile, HF broadcasting, and new space matters in 1992 (WARC–92).

WARC–59 had a special significance for radio astronomy for two reasons: 1) radio astronomy was recognized as a radio communications service, and 2) a series of frequency bands was allocated for use by radio astronomy as “windows” through which radio astronomers could study the universe. These frequency bands were reviewed by subsequent radio conferences, including WARC–92 and WRC–95.

Endnotes

(1)National Telecommunications and Information Administration, U.S. Department of Commerce, NTIA Special Publication 91–23, U.S. Spectrum Management Policy: Agenda for the Future (1991) [hereinafter NTIA Spectrum Policy Study].

(2)National Telecommunications and Information Administration, U.S. Department of Commerce, NTIA Special Publication 94–31, U.S. National Spectrum Requirements: Projections and Trends (1995) [hereinafter NTIA Requirements Study].

(3)National Telecommunications and Information Administration, U.S. Department of Commerce, NTIA Special Publication 95–34, Land Mobile Spectrum Planning Options (1995).

(4)National Telecommunications and Information Administration, U.S. Department of Commerce, NTIA Special Publication 96–332, High Frequency (3–30 MHz) Spectrum Planning Options (1996) [hereinafter HF Report].

(5)In the NTIA Requirements Study, the amateur community also expressed a need for spectrum above 30 MHz, but that requirement will be addressed separately.

(6)The National Table of Frequency Allocations is comprised of the U.S. Government Table of Frequency Allocations and the FCC Table of Frequency Allocations. The National Table indicates the normal national frequency allocation planning and the degree of conformity with the ITU Table of Frequency Allocations.

(7)Copies of the NTIA new spectrum wall chart, the NTIA Manual, the Extract of the NTIA Manual (containing the National Table of Frequency Allocations) and the FCC Rules (Parts 1 to 19) containing the National Table of Frequency Allocations are available from the Government Printing Office (GPO) or from the NTIA homepage: www.ntia.doc.gov. For ordering information and GPO address, contact Norbert Schroeder, Vice–Chairman, Interdepartment Radio Advisory Committee (ph: 202–482-3999, fax: 202- 501–6198, or email: nschroeder@ntia.doc.gov).

(8)To obtain complete allocation information (internationally), the current version of Article 8 of the ITU Radio Regulations must be examined.