North American AstroPhysical Observatory (NAAPO) Cosmic Search: Issue 6 (Volume 2 Number 2; Spring (Apr., May, June) 1980) [Article in magazine started on page 40]

Allocating the Radio Spectrum By: Vernon Pankonin The World Administrative Radio Conference (WARC), which was held in Geneva, Switzerland, during October and November 1979, performed a complete review of the International Radio Regulations which include a Table of Frequency Allocations. In the allocations table, the radio spectrum from 9 kHz to 275 GHz is partitioned into frequency bands for use by thirty-one radio communication services of which radio astronomy is one. The Radio Regulations are administered by the International Telecommunications Union (ITU), which is a specialized agency of the United Nations. Approximately 144 of the 154 member countries of the ITU sent a total of about 2200 delegates to the WARC. The U.S. delegation numbered 65. Radio astronomy was accepted as a radio service at the last general WARC in 1959, and it was awarded protection in a few frequency bands. However, it was a young science then, and its needs have greatly expanded and changed as it has matured. Now any band in the radio spectrum can be covered at one or more of the major radio observatories around the world. At the same time that the requirements of radio astronomy have become broader and more stringent, the competition for the limited spectrum has become increasingly severe. Radio astronomy and some space services are unique in the radio communications field in that they are entirely passive, that is, they only receive and do not transmit. Also a typical observation requires a sensitivity to extremely low levels of radiation which makes radio astronomy particularly susceptible to man-made transmissions. The technical arm of the ITU, the International Radio Consultative Committee (CCIR), has defined realistic levels of harmful interference to radio astronomy observations in a report, which severely restricts the possibilities of the active and radio astronomy services sharing a frequency band. The convening of WARC-79 was announced several years ago, and radio astronomers have expended considerable effort to formulate an international position in order to present a united front. They have adopted the posture that protection should be sought: (1) for continuum bands at octave intervals throughout the spectrum above 10 MHz with at least a 1 percent bandwidth in each band, and (2) for approximately 20 lines emitted from molecules and atoms which are considered of prime astrophysical importance. For the latter, the bandwidth should be ±0.1 percent (±300 kilometers per second Doppler shift) centered on the rest frequency of the line to accommodate, to a certain extent, the motions of the sources relative to the Earth. Continuum observations require relatively wide bandwidths for increased sensitivity, but the center frequencies of the bands are fairly flexible. On the other hand, the frequencies for spectral line observations are fixed by nature, and relatively narrow bandwidths are sufficient. Although the radio astronomers could agree fairly easily amongst themselves on the requirements of the science, proposals to the Conference could only be submitted by national members. National positions for the WARC were developed over several years, and the status of radio astronomy in a given nation's proposals largely depended on the success of radio astronomers in their domestic preparations. Hence, the radio astronomy positions of the countries varied widely. The last possibility for negotiation was during the deliberations of the Conference itself, and there were radio astronomers on the delegations of Argentina (Bajaja), Australia (Whiteoak), Canada (Doherty), the Federal Republic of Germany (Grahl), India (Swarup), the Netherlands (Kahlmann and Schilizzi), Nigeria (Okoye), the Soviet Union (Dubinsky), the United Kingdom (Homer), and the United States (Pankonin). The International Radio Regulations provide several levels for protecting radio services from mutual interference. The highest level of protection is a primary, exclusive allocation in a frequency band; that is, only one service is authorized to operate in a given band. The second level is also a primary status but the same band is shared on an equal basis with one or more additional services. The third level is called secondary, where a service is authorized to operate but may not interfere with other services in that band which have primary status. The fourth level offers no formal protection but is a notification that a service is using the band. This last type is often used for spectral line observations, and it simply calls attention to the use of the band by radio astronomy and asks for protection when practicable. The protection for radio astronomy in the International Radio Regulations before and after WARC-79 is summarized in Tables 1 and 2. Radio astronomers certainly did not achieve all of their goals, but in general their position was improved at the WARC. Although considerable gains in formal protection were made at frequencies above 40 GHz, the most significant general improvement was in the standardization and strengthening of the radio astronomy footnotes. Radio astronomers have made liberal use of footnotes in many frequency bands, and the application of these has now been made consistent and uniform. Footnotes now appear in practically every band where radio astronomy has an allocation or notification of use, and the texts have been standardized. The new footnotes are of two types (applied as indicated in Table 2) which, with certain minor variations, all contain the wording given at the bottom of Table 2. Other notable actions at the WARC include an article which was added to the Radio Regulations to emphasize some of the special problems faced by radio astronomers, and to give examples of the practicable steps for protection which are alluded to in the footnotes. Radio astronomers have long realized that the far side of the Moon could provide a protected zone which is naturally shielded from transmissions on or near the Earth, and that at some point in the future it may be necessary and feasible to operate from such a distant base. An article was added to the Radio Regulations giving protection to radio astronomy and other passive services in the lunar shielded zone over most of the radio spectrum. Also a footnote was inserted in appropriate bands calling attention to the search for signals transmitted by extra-terrestrial intelligence (SETI) which reads as follows: In the bands 1400 to 1427 MHz, 101 to 120 GHz, and 197 to 220 GHz, passive research is being conducted by some countries in a programme for the search for intentional emissions of extra-terrestrial origin. The radio regulations which were formulated at the WARC-79 have the force of an international treaty for a country once the Final Acts are signed (and in the United States ratified by the Senate). According to the schedule, the new radio regulations will take effect January 1, 1982, and they are expected to remain in force without major revision until the end of this century. These regulations, however, only provide for the allocation of frequency bands to radio services on the international level. Additional protection for radio astronomy is necessary and can be achieved by enlightened assignment of frequencies within a band to stations of an authorized service, by effective compliance checking, and by adequate technical standards for equipment. All of these areas are tasks of the individual national administrations. Thus, the radio astronomers' efforts do not end with WARC-79. Representation must also be maintained in the daily regulatory process in each country. Vernon Pankonin was born in Ogallala, Nebraska, in 1946. He received the B.S. degree in physics and mathematics from the University of Nebraska (Lincoln) in 1968 and the Ph.D. degree in astronomy from Cornell University in 1973. He was guest scientist and later assistant staff scientist at the Max-Planck-Institute for Radioastronomy, Bonn, West Germany from 1973 to 1979. Since September 1979 he has been Radio Spectrum Manager at the U.S. National Science Foundation, Washington, D.C. Dr. Pankonin was an official U.S. delegate to the WARC-79 conference in Geneva, Switzerland. Radio Services and Nomenclature Some of the services with which radio astronomy shares the frequency spectrum are broadcasting (AM. FM and TV), aeronautical radio communication, aeronautical radio navigation, maritime radio communication, maritime radio navigation, radio location (radar), land mobile communication, fixed point-to-point communication, amateur, earth-space communication, communication between space stations and standard frequency and time transmissions. In the U.S., radio regulations are administered by the Federal Communications Commission (FCC), Washington. D.C. 20554. Copies of the current Rules and Regulations of the FCC are available from the Superintendent of Documents, Government Printing Office, Washington, D.C. 20402. In the accompanying article with tables on radio astronomy frequency allocations, the term continuum refers to the fact that many cosmic radio sources emit continuously over a wide band of frequencies or wavelengths. Radio astronomy observations of this continuum radiation can be accomplished with a number of protected channels located at intervals throughout this band. Although the exact frequency or wavelength of these channels is not critical for continuum observations this is not the case for observations of another type of cosmic radio radiation from molecules or atoms, each of which has a characteristic frequency or wavelength called a line. Examples are the atomic hydrogen line at 1400 to 1427 megahertz (21 centimeters), deuterium (heavy hydrogen) at 322 to 328.6 megahertz (92 centimeters), the hydroxyl radical (OH) at 1610.6 to 1722.2 megahertz (18 centimeters), etc, -Eds. [Note. Tables 1 & 2 below have been reformatted in this webpage from the versions in the magazine as follows: (1) the tables are organized like spreadsheets with grid lines (borders) showing; and (2) the Frequency Band has been divided into three columns with the labels: Low (meaning frequency at the low end of the band), High (meaning frequency at the high end of the band), and Units (meaning the frequency units used).] —Webpage Editor TABLE 1 RADIO ASTRONOMY ALLOCATIONS (prior to WARC-79) Frequency Band     Low High Units Protection Status Principal Use 21850 21870 kHz PRIMARY exclusive Continuum 37.75 38.28 MHz Secondary Continuum 73 74.6 MHz PRIMARY exclusive (only in Regions 2 & 3)* Continuum 150.05 153 MHz PRIMARY shared with active (only in Region 1) Continuum 322 328.6 MHz Notification of Use Continuum 406.1 410 MHz PRIMARY shared with active Continuum 608 610 MHz PRIMARY exclusive in Region 2. Notification of Use in Regions 1 & 3 Continuum 1350 1400 MHz Notification of Use Redshifted hydrogen 1400 1427 MHz PRIMARY exclusive Hydrogen 1611.5 1612.5 MHz Notification of Use Hydroxyl 1660 1670 MHz PRIMARY shared with active Hydroxyl 1720 1721 MHz Notification of Use Hydroxyl 2670 2690 MHz Notification of Use Continuum 2690 2700 MHz PRIMARY exclusive Continuum 4825 4835 MHz Notification of Use H2CO 4950 4990 MHz Notification of Use Continuum 4990 5000 MHz PRIMARY exclusive in Region 2. PRIMARY shared with active in Regions 1 & 3 Continuum 5750 5770 MHz Notification of Use Continuum 10.6 10.68 GHz PRIMARY shared with active Continuum 10.68 10.7 GHz PRIMARY exclusive Continuum 14.485 14.515 GHz Notification of Use H2CO 15.35 15.4 GHz PRIMARY exclusive Continuum 22.21 22.26 GHz PRIMARY shared with active H2O 23.6 24 GHz PRIMARY exclusive Continuum & ammonia 31.2 31.3 GHz Notification of Use Continuum 31.3 31.5 GHz PRIMARY exclusive Continuum 36.458 36.488 GHz Notification of Use H+ 52 58.2 64 54.25 59 65 GHz Passive bands but no notification of use for radio astronomy Continuum 86 92 GHz PRIMARY shared with passive Numerous lines 101 102 GHz Passive band but no notification of use for radio astronomy Continuum 115.16 115.38 GHz Notification of Use CO 130 140 GHz PRIMARY shared with passive Continuum 182 185 GHz Passive band but no notification of use for radio astronomy H2O 230 240 GHz PRIMARY shared with passive CO * In the International Radio Regulations, the world is divided into three regions. Roughly Region 1 comprises Europe and Africa, Region 2 is the Western Hemisphere, and Region 3 is Asia and Australia. TABLE 2 RADIO ASTRONOMY ALLOCATIONS (WARC-79) Frequency Band     Low High Units Protection Status (Footnote Type) Principal Use 13360 13410 kHz PRIMARY shared with active (2) Continuum 25550 25670 kHz PRIMARY exclusive (special) Continuum 37.5 38.25 MHz Secondary (2) Continuum 73 74.6 MHz PRIMARY exclusive in Region 2 (no footnote). Notification of Use in Regions 1 & 3 (2) Continuum 150.05 153 MHz PRIMARY shared with active only in Region 1, Australia, India (2) Continuum 322 328.6 MHz PRIMARY shared with active (2) Continuum & deuterium 406.1 410 MHz PRIMARY shared with active (2) Continuum 608 614 MHz PRIMARY (active secondary) in Region 2 (no footnote). Permitted in African Broadcast Area; secondary in Regions 1 & 3 (2) Continuum 1330 1400 MHz Notification of Use (2) Hydrogen 1400 1427 MHz PRIMARY - passive band (1) Hydrogen 1610.6 1613.8 MHz Secondary (2) Hydroxyl 1660 1660.5 MHz PRIMARY shared with active (2) Hydroxyl 1660.5 1668.4 MHz PRIMARY (active secondary) (2) Hydroxyl 1668.4 1670 MHz PRIMARY shared with active (2) Hydroxyl 1718.8 1722.2 MHz Secondary (2) Hydroxyl 2655 2690 MHz Secondary (2) Continuum 2690 2700 MHz PRIMARY - passive band (1) Continuum 3260 3332 3345.8 3267 3339 3352.5 MHz Notification of Use (2) CH 4800 4990 MHz Secondary (2) Continuum & H2CO 4990 5000 MHz PRIMARY shared with active (2) Continuum 10.6 10.68 GHz PRIMARY shared with active (2) Continuum 10.68 10.7 GHz PRIMARY - passive band (1) Continuum 14.47 14.5 GHz Secondary (2) H2CO 15.35 15.4 GHz PRIMARY - passive band (1) Continuum 22.01 22.21 GHz Notification of Use (2) H2O 22.21 22.5 GHz PRIMARY shared with active (2) H2O 22.81 23.07 22.86 23.12 GHz Notification of Use (2) NH3 23.6 24 GHz PRIMARY - passive band (1) Continuum & ammonia 31.2 31.3 GHz Notification of Use (2) Continuum 31.3 31.5 GHz PRIMARY - passive band (1) Continuum 31.5 31.8 GHz PRIMARY - passive band in Region 2 (1). PRIMARY (active secondary) in Regions 1 & 3 (2) Continuum 36.43 36.5 GHz Notification of Use (2) H+ 42.5 43.5 GHz PRIMARY shared with active (2) Continuum & Si0 48.94 49.04 GHz PRIMARY shared with active (2) CS 51.4 58.2 64 54.25 59 65 GHz Notification of Use - passive bands (1) Continuum 72.77 72.91 GHz Notification of Use (2) H2CO 86 92 GHz PRIMARY - passive band (1) Numerous lines 93.07 93.27 GHz Notification of Use (2) HNN+ 97.88 98.08 GHz PRIMARY shared with active (2) CS 105 116 GHz PRIMARY - passive band (1) CO 140.69 144.68 145.45 146.82 140.98 144.98 145.75 147.12 GHz PRIMARY shared with active (2) H2CO DCN H2CO CS 150 151 GHz Secondary (2) NO, H2CO 164 168 GHz PRIMARY - passive band (no footnote) Continuum 174.42 177 178.2 181 175.02 177.4 178.6 181.6 GHz Secondary (2) C2H HCN HCO+ HNC 182 185 GHz PRIMARY - passive band (1) H2O 186.2 186.6 GHz Secondary (2) HNN+ 217 231 GHz PRIMARY - passive band (1) CO 250 251 GHz PRIMARY - passive band (2) NO 257.5 258 GHz Secondary (2) NO 262.24 262.76 GHz PRIMARY shared with active (2) C2H 265 275 GHz PRIMARY shared with active (2) HCN, HCO+, HNC 278 343 280 348 GHz Notification of Use (not allocated) HNN+ CO Footnote Types: 1. All emissions in the band between frequencies listed are prohibited. 2. In making assignments to stations ..... administrations are urged to take all practicable steps to protect the radio astronomy service from harmful interference. Emissions from space or airborne stations can be particularly serious sources of interference to the radio astronomy service.