The European Science Foundation is an
association of its 62
member research councils and academies in 21 countries. The
ESF brings European scientists together to work on
topics of common concern, to co-ordinate the use of expensive
facilities, and to discover and define new endeavors that will
benefit from a co-operative approach
On behalf of European radio astronomers, the ESF Committee on
Radio Astronomy Frequencies, CRAF, coordinates activities to
keep the frequency bands used
by radio astronomers free from interference.
The scientific work sponsored by ESF includes basic research in the natural sciences, the medical and biosciences, the humanities and the social sciences.
The ESF links scholarship and research supported by its members and adds value by cooperation across national frontiers. Through its function as coordinator, and also by holding workshops and conferences and by enabling researchers to visit and study in laboratories throughout Europe, the ESF works for the advancement of European science.
On behalf of European radio astronomers, the ESF Committee on
Radio Astronomy Frequencies, CRAF, coordinates activities to
keep the frequency bands used
by radio astronomers free from interference.
The turn of the year reminds us that the times move on. Circumstances are not fixed, and the changing tides of history throw up new situations and opportunities.
The 23rd General Assembly of the Internatianal Astronomical Union in August 1997 saw a rising awareness of radio astronomy interference issues. In addition to the specialist discussion meetings an unprecedented meeting of radio observatory directors was convened, which resulted in the Kyoto Declaration. This document, which is reproduced in Section 4, pledges increased support to radio astronomy frequency protection activities. One of the first concrete steps in this direction is the appointment of the first full-time spectrum manager for European Radio Astronomy, Titus Spoelstra, our CRAF Secretary. We wish Titus many successes in the coming years. It is fitting that this milestone was achieved in the year of CRAF's 10th anniversary.
The New Year sees the start of preparations for WRC-99. Radio astronomy made significant gains at WRC-97, including improved footnote protection of low frequency bands from the unwanted emissions of satelite downlinks below 1 GHz (little LEOs). The agenda for WRC-99 contains some very important issues for radio astronomy. The levels of spurious emissions from spacecraft, not concluded by TG1-3 or WRC-97, will be settled at WRC-99. Most importantly the allocation of frequencies above 71 GHz to passive services, including radio astronomy, will be reviewed. CRAF has already been working on the improvement of protection for mm-wave astronomy for some years. Our closer liason with the remote sensing community now provides the opportunity to present an integrated proposal from the passive services, which serves the needs and improves the regulatory position of radio astronomy and remote sensing.
We must ensure that the passive services get a better deal than passive smokers.
R.J.Cohen - Jodrell Bank
The 24rd CRAF meeting was held at Eidgenössische Technische Hochschule in Zürich, ETHZ. The third day of the meeting was reserved for a technical discussion about the MSS-radio astronomy sharing issues in the 1.6 GHz frequency domain, the Iridium system in particular.
Following the CRAF policy statement (agreed in the 23rd CRAF meeting in St.Petersburg) concerning the relation between radio astronomy and Iridium/Motorola in Europe this CRAF meeting was open for Motorola to attend. This agreement implied that in cases that Motorola would approach a radio observatory to discuss the issue of sharing between radio astronomy and the Iridium system at 1.6 GHz, Motorola would be told to contact the CRAF secretary: Motorola would then be invited to the 24th CRAF meeting. Since the 23rd CRAF meeting Motorola had been informed verbally (in several occasions) to be welcome at this meeting. But Motorola did not respond and since Motorola did not attend, the 3rd day of this meeting was cancelled.
The 24th CRAF meeting was also attended by representatives of the (passive) remote sensing community. CRAF welcomes the possibility of cooperation with other passive scientific users of the radio spectrum. The need for this became clear when the CEPT project on new allocations above 105 GHz was discussed: the pressure on these frequencies is becoming higher, which was obvious from a recent CEPT FM meeting where Luxemburg expressed strong objections against the allocation of frequency bands exclusively to passive services. A new CEPT FM project team (PT33) was installed to study the problem of passive frequency allocations above 105 GHz. CRAF and representatives from the remote sensing community will participate.
Other activities in CEPT projects:
Work in the CEPT SE project teams SE21, 27 and 28 continued. In SE21 CRAF drew the attention to the fact that the draft ITU-R SM.329-7 recommendation which contains the results of the ITU-R TG1-3 work on spurious emissions, does not provide proper category-A limits in cases were the application uses very narrow bandwidths. Another uncertainty is the question how to consider radiation which is still transmitted when a carrier signal has been switched off.
SE27 discussed progress in Terrestrial Digital Video Broadcasting - TDVB, which will make use of the "classical" TV-broadcasting frequencies below 1 GHz.
CRAF defended the case of radio astronomy very strongly in SE28. Unclarity and defects were brought to the attention of the SE28 chairman. However, the CEPT did accept the SE28 chairman's report and the SE28 findings concerning radio astronomy are now brought to the attention to the European administration and their support is sought. A newly installed CEPT Milestone Review Committee has one of its tasks: to handle any difficulty arising, including the radio astronomy problem.
The CRAF Handbook for Radio Astronomy is well received world- wide. The CRAF information on the WWW has been visited already by users from more than 40 countries (more than 18% of them from industry). On the CEPT ERO WWW-homepage a direct link to CRAF has been installed. CRAF has also direct liaisons with administrations outside Europe, i.e. the USA and China, while as a result of CRAF action, China did recently install a national "CRAF", while it will also participate in a Asia-Pacific Rim kind of "CRAF".
Much time of the meeting was devoted to detailed strategy discussions. As a public result of this CRAF will held a workshop on the issue of "how much data can be lost due to propagation and interference" early 1998 in Nançay. The CRAF frequency manager, dr.T.A.Th.Spoelstra, is already active in this position for 100% of his time.
The 23rd General Assembly of the International Astronomical Union, IAU, was held during August 17-30, 1997, in Kyoto, Japan. As usual the General Assembly of the IAU discussed the protection of radio astronomy frequencies at many occasions.
At this General Assembly, Dr.J.B.Whiteoak and Prof.Dr.R.S.Booth, respectively Chairmen of the Commission for Radio Astronomy of IAU and the International Union of Radio Science, called a meeting of Directors of Radio Astronomy Observatories to discuss the problems of interference. This is becoming very serious because of the proliferation of users of the radio spectrum and a particular threat is posed by low earth orbit satellite to be used e.g. for mobile telephones.
The meeting resulted ultimately in the Kyoto Declaration.
During this session some radio astronomy experts in frequency protection activities introduced the topic in a tutorial manner to the audience.
Dr. J. B. Whiteoak (ATNF, Australia) presented an outline on Frequency Protection efforts within the ITU-R structure, how the system works, who is working, and what may be achieved. This introduction was particularly helpful for people who were not fully informed of the intricate organizational structure of the ITU-R.
Dr. W. A. Baan (Arecibo, USA) presented a status report on Iridium Coordination and the many LEO systems and where are we going.
Dr. P. Jewell (JCMT, USA) presented some of the ideas being relating to the protection of millimetre bands. A basic premise should be for the RAS to get access to as much of the mm-wave spectrum as possible, by time and geographical sharing or by allocation. A more extensive report of the activities of MMWG at IAU GA follows below.
Dr. H. R. Butcher (NFRA, Netherlands) presented a description of the activities of the OECD (Organization for Economic and Cultural Development) MegaScience Forum Working Group on Radio Astronomy. Radio Astronomy is only one of four topics that are being considered by the Forum. Dr.Butcher chairs this RA session. OECD is willing to support our efforts to protect the radio spectrum and is looking for practical ways to do this. Two representatives of OECD were present at this meeting.
Dr. R. J. Cohen (Jodrell Bank, UK) presented an outline of a draft document on radio astronomy frequency protection and on ways to increase protection in the future. This outline was prepared in the framework of the OECD Megascience Forum by himself and Dr. R. D. Ekers (ATNF, Australia).
The following discussions centred less on how the directors can support the ongoing RFI efforts but more on the way OECD can help in this effort. It was not clear what role OECD can play in the arena of the ITU allocation process and how to exert pressure on the relevant institutions. During the meeting Dr. R. S. Booth (Onsala, Sweden) proposed a draft declaration of unity of the world's observatory directors. This "Kyoto Declaration" describes the increasing interference problems experienced by the radio astronomers and proposes to battle this problem through vigilance, education of other spectrum users and in-house research. Strong support is expressed for the activities of IUCAF (the Inter-Union on the Allocation of Frequencies), CRAF and CORF (the Committee on Radio Frequencies of the US National Research Council).
Introduction to the KYOTO DECLARATION
Radio astronomy observations have, for many years, been troubled by the effects of interference. Early problems were motor car ignition systems which disturbed low frequency observations, or electric fences whose pulsed signals sometimes confused pulsar observers. Although annoying at the time, these sources of interference were recognizable and could often be suppressed - they now seem trivial compared to today's problems. Today, TV companies blatantly transmit in the protected band at 1420 MHz, the frequency of the important hydrogen line, and fixed radio links in the vicinity of Jodrell Bank can affect observations in the radio astronomy band at 1666 MHz. But even these somewhat localized problems seem minor compared to the threat posed by tomorrow's ubiquitous satellite transmissions. There will be no escape - no radio observatory, no matter how remote, will be immune.
The radio spectrum is shared among users under the auspices of the International Telecommunications Union, ITU, which assigns specific bands to the various 'services', including radio astronomy. The ITU cuts the spectrum into slices, like a cake, but by their very nature, radio transmissions cannot be cut to zero at band edges. This would not be a problem to passive users of the spectrum, like radio astronomers, if transmitter frequencies were kept well away from our designated bands, but the proliferation of active users is putting such pressure on the available spectrum that we are finding, for example, satellite transmissions in bands adjacent or close to the radio astronomy bands. Radio astronomy systems are so sensitive that unwanted emissions from such satellite transmitters which fall outside the satellite band, but within the radio astronomy band, can cause severe interference, making the observations useless.
Such is the global nature of the threat posed by low-earth orbit satellites used for mobile telephones, for example, that the directors of many of the world's radio astronomy observatories met in Kyoto at the IAU General Assembly to discuss the problem and determine what action to take. They realize that they must be diligent and that they must co-ordinate their efforts, but that the onus lies with them to tackle the problem not just through their administrations, but by a process of education of the public and of the communications community. Furthermore, they realize that they must double their technical efforts to build low-loss filters and other systems to mitigate the effects of interference. At the same time they will continue to urge the telecommunications industry and the radio spectrum managers to take cognizance of the dangers to radio astronomy of over development of the radio spectrum. As a measure of their resolve, they have agreed to sign the KYOTO DECLARATION.
THE KYOTO DECLARATION
As directors of the world's radio observatories, we note the increasing use of the radio spectrum by commercial and other interests. While recognizing the economic importance of such use, we are concerned that it should not harm radio astronomy, a uniquely powerful means for the study of the Universe. To protect the benefits of radio astronomy to humankind, we resolve to undertake the following initiatives. We will conduct a programme of activities to educate our fellow scientists, the telecommunications industry, and the general public to the necessity of protecting radio astronomy's spectrum requirements. Further, we will study technical means to mitigate the problem of interference.
We endorse the formation of the OECD Megascience Forum Working Group on Radio Astronomy and will support it in its efforts to inform science policy makers of radio astronomy's concerns in the area of spectrum management. Additionally, we will all intensify participation in the regulatory processes conducted through IUCAF (the Inter Union Committee on the Allocation of Frequencies) and by the International Telecommunications Union and its member nations' agencies by increasing the number of personnel and resources devoted to spectrum management.
In order to make our actions more effective we agree to increase the level of co-ordination between the world's radio observatories so that we can present a common position on issues of radio spectrum management. In North America and Europe co-ordinating groups already exist (CORF, the Committee on Radio Frequencies, and CRAF, the Committee for Radio Astronomy Frequencies) and we endorse proposals to generate similar co-ordinating groups in the Asia-Pacific region and in South America.
Kyoto, Japan, at the XXIIIrd General Assembly of the International Astronomical Union, August 1997.
DECLARATION signed by:
Baudry, A. - Observatoire de Bordeaux, France
Blitz, L. - Univ. of California, Berkeley CA, US
Butcher, H.R. - Netherlands Foundation for Research in Astronomy
Booth, R.S. - Swedish National Facility for Radio Astronomy, OSO
Bronfman, L. - Universidad de Chile
Davies, R.D. - Nuffield Radio Astronomy Laboratories, Jodrell Bank, UK
Dewdney, P. - Herzberg Institute of Astrophysics, DRAO, Canada
van Driel, W. - Station de Radioastronomie, Nançay, France
Ekers, R.D. - Australia Telescope National Facility
Goldsmith, P. - Arecibo Observatory, Puerto Rico
Gomez-Gonzales, J. - Cientro Astronomica de Yebes, Spain
Green, A. - Molonglo Observatory, Australia
Grewing, M. - Institute de Radio Astronomie Millimétrique, IRAM, France
Hills, R. - Mullard Radio Astronomy Observatory, UK
Hirabayashi, H. - Institute of Space & Astronautical Science, ISAS, Japan
Ishiguro, M. - Nobeyama Radio Observatory, Japan
Johnston, K. - U.S. Naval Observatory, US
Kandalyan, R. - Byurakan Observatory, Armenia
Kapahi, N.R. - National Centre for Radio Astrophysics, TIFR, India
Kuiper, T. - Jet Propulsion Laboratory, DSN, US
Lo, K.Y. - Academia Sinicia, ASIAA, Taiwan
Mattila, K. - Helsinki University Observatory, Finland
McCulloch, P. - Univ. of Tasmania, Australia
Morton, D.C. - Herzberg Institute of Astrophysics, DRAO, Canada
Nicolson, G. - Hartebeesthoek Radio Astronomy Observatory, South Africa
Padrielli, L. - Istituto di Radioastronomia, CNR, Italy
Robson, I. - James Clerk Maxwell Telescope, JCTM, Hawaii, US
Salah, J. - MIT Haystack Observatory, US
Sargent, A. - California Institute of Technology, US
Schilizzi, R.T. - Joint Institute for VLBI in Europe, JIVE, Netherlands
Shapiro, I. - Harvard-Smithsonian Center for Astrophysics, US
Snyder, L.E. - Univ. of Illinois, US
Urpo, S. - Metsahovi Radio Research Station, Finland
Vanden Bout, P. - National Radio Astronomy Observatory, US
Wielebinski, R. - Max-Planck-Institut für Radioastronomie, Germany
Zhao, Junliang - Shanghai Observatory, China
The bi-annual World Radiocommunication Conference (WRC-97) has been held in Geneva from October 27 to November 21, 1997. A World Radiocommunication Conference (WRC) follows the agenda adopted for it by the previous WRC. Furthermore, a WRC also adopts a "draft-agenda" for the first conference after the next one.
Radio astronomy issues were not on the Agenda for the WRC-97. They were only issues of peripheral interest. The participation from both the radio astronomy and Earth exploration communities was strong during the Conference, and both the Earth exploration delegation (EES) and the radio astronomers (RAS) did very well on almost all issues.
Dr.P.VandenBout, director of the National Radio Astronomy Observatory (USA), spend four days as a USA delegate at the Conference and presented a lunch talk on "What do the Radio Astronomers use all that radio spectrum for ?." The USA Ambassador to the Conference gave a short introduction and stayed to listen.
This report is based on the IUCAF report of this conference (see for details: IUCAF).
1.1 The Radiocommunication Assembly
The Radiocommunication Assembly was held during the week before the Conference. During this meeting the results and Recommendations from the ITU-R Study Groups were considered. Boris Doubinsky (Russia) represented IUCAF during this meeting.
The only issue at the RA for the RAS was a Recommendation from ITU-R Study Group 8 (Doc 8/1021) on the "Principles and Methodology for Frequency Sharing in the 1610.6 - 1613.8 MHz and 1660.0 - 1660.5 MHz Bands between MSS (Es) and the RAS". This Draft New Recommendation, describing a Monte Carlo methodology to calculate the interference from MSS terminals into a telescope, has been under discussion in ITU-R Working Party 7D for several meetings, because of the immaturity of the document. However, the MSS people wanted to start working on this and submitted it to the RA. In the meantime, some mutually agreed upon text of "recommends 3" saying "that in any application of a methodology, the input parameters should be agreed by the parties concerned during coordination" had been dropped (accidentally) in the submitted version.
1.2 WRC-97 Conference Report
As already mentioned above, the WRC-97 agenda contained only issues indirectly related and of importance for radio astronomy. Since the agenda for WRC-99 contains at least 15 items which are of direct importance for radio astronomy, the radio astronomy community will need to prepare thoroughly for the astronomy issues on this agenda. Since the issues also include the radio astronomy bands above 71 GHz, CRAF's activities in CEPT PT33 are carried out with the WRC-99 in mind as well.
- The following general trends are especially relevant for radio astronomy:
- specific issues:
Because of the continued participation of IUCAF in TG1/3 and the new TG1/5, and the participation at the Conference, has raised the general awareness of the issue of harmful interference for particularly the passive services. Harmful Interference was an important issue for many services during many discussions.
The modified Appendix S3 now contains two Sections: Section I with old standards for systems installed on or before Jan 2003 (valid until 1 January 2012), which apply to system up to 17.7 GHz. Section II with new standards for all systems installed after Jan 2003 and to all transmitters after January 2012. We will have to wait six years before the (inadequate) Cat. A limits will be generally enforced.
The idea from Canada that "the protection of stations in the RAS should not unduly burden other spectrum users and particularly the space services" does not feature in the newly revised Recommendation 66. Although the IUCAF position was that the protecting the passive services should not be solved on a "case-by-case" basis, this concept has crept into the Recommendation 66. However, a balanced view has been expressed with the wording of "the impact of implementing or not implementing these limits" (see item f). The dominant perception at the Conference appeared to be that "general spurious limits" should not be used to protect the passive services.
- bands below 1 GHz:
- bands between 1 and 3 GHz:
- bands above 10 GHz:
- FSS at ~15 GHz:
The non-GSO FSS feeder link allocation had been allocated at WRC-95 in the band 15.4 - 15.7 GHz, which is adjacent to the primary RAS band 15.35 - 15.4 GHz has been modified as follows:
|15.4 - 15.43||Aeronautical Radio Navigation||S5.511A|
|15.43 - 15.63||Fixed-Satellite Service (sE)(Es)||S5.511A|
|Aeronautical Radio Navigation||S5.511C, S5.511D|
|15.63 - 15.7||Aeronautical Radio Navigation||S5.511D|
S5.511A specifically states that FSS (space-to-Earth) shall not cause harmful to RAS stations in the band 15.35 - 15.4 GHz. The required protection levels are in RA.769 and special measures are to be employed to protect the RAS.
S5.511D states specific pfd limits and coordination procedures (Resolution 46) are mentioned in order to protect the Aeronautical Radio Navigations operations in these bands.
It appears unlikely that this band can be used at all for FSS (space-to-Earth). The American Ellipso plans to use this band in (Earth-to-space) direction. A Russian system is planned for the (space-to-Earth) direction. It will be difficult to implement these systems.
Resolution COM5-8 calls for studies of the "Feasibility of Implementing Feeder Links" in this band. The needs in the RAS are strongly considered in Resolution COM5-8 because the Aeronautical Radio Navigation service also want to keep these feeder links out of this band. See WRC-99 Agenda item 1.14 (below).
- FSS at ~ 42 GHz.
The band 40.5 - 42.5 GHz has been provisionally allocated to Fixed Satellite Service (space-to-Earth) subject to Resolution COM5-16. This band is adjacent to the 42.5 - 43.5 GHz RAS band in Regions 1 and 3. In the USA the upper 1 GHz of the band is used for other purposes and particular this part is subject to Resolution COM5-16. Resolutions COM5-16, COM5-17, and COM5-29 are in WRC-99 Agenda Item 1.4 (see below).
Resolution COM5-16 addresses the protection of the RAS in the adjacent bands from services in the band 41.5 - 42.5 GHz.
Resolution COM5-17 addresses the criteria and methodologies for sharing between FSS and other services in the band 40.5 - 42.5 GHz.
Resolution COM5-29 resolves to study the use of the 40.5 - 42.5 GHz band by the FSS.
- Cloud radar at ~94 GHz:
The allocation of the 94 - 94.1 GHz band for space-based active earth sensors has been extensively coordinated with the radio astronomy community. The specific frequency range has been chosen based on the advise from the radio astronomy community. The Conference added EES (active) and SR (active) to this band while maintaining the Radiolocation allocation but suppressing the Fixed, Mobile, and FSS (Es) allocations. A new footnote RR S5.562 has been added to the 94 - 94.1 GHz band to reserve this for cloud radars only.
FSS above 30 GHz:
Resolution COM5-7 relates to the Use of the two bands by HAPs in the Fixed Service. This Resolution takes proper account of the protection of the two Primary RAS allocations in the bands 42.5 - 43.5 GHz and 48.94 - 49.09 GHz. (WRC-99 Agenda Item 1.5 - see below).
Resolution COM5-11 resolves to study the band 31.8 - 33.4 GHz for High Density FS systems.
Resolution COM5-12 resolves to study bands above 30 GHz to find bands available for High Density applications in the Fixed Service.
Resolution COM5-28 resolves to study the sharing between the FS and other services in the band 37 - 40 GHz.
2. The agenda of WRC-99 and WRC-01 and radio astronomy
2.1 Agenda WRC-99 (following each item by number):
1.2 finalize the remaining issues on spurious emission in Appendix S3 for space services;
1.4 consider issues relating to allocations and regulatory aspects related to Resolution COM5-16 (40.5 - 42.5 GHz FSS (space-to-Earth)) and others;
1.5 consider regulatory provisions and possible additional frequency allocations for services using HAPs taking into account the results of Resolution COM5-7;
1.6.1 review the spectrum requirements for the operation of terrestrial IMT-2000 with the view to identify future expansion bands and adjustments to the Table of Allocations;
1.9 take into account the results of ITU-R studies in evaluating the feasibility of an allocation in the space-to-Earth direction to the MSS in a portion of the 1559 - 1567 MHz frequency range, in response to Resolutions 213 and COM5-31;
1.10 to consider the results of ITU-R studies in accordance with Resolution COM5-24 (Use of the bands 1525 - 1559 MHz and 1626.5 - 1660.5 MHz by the MSS);
1.11 consider constraints on existing allocations and to consider additional allocations on a worldwide basis for the non-GSO/MSS below 1 GHz, taking into account Resolutions 214 (Rev WRC-97) and COM5-25 (406 MHz);
1.13 on the basis of the results of the studies in accordance with Resolution COM5-18 on the "Use of NGSO systems in the FSS in certain frequency bands"
1.14 review the results of the studies on the feasibility of implementing non-GSO MSS feeder links in the 15.43 - 15.63 GHz range in accordance with Resolution COM5-8;
1.15.1 to consider new allocations to the radionav-satellite service required to support developments in the range from 1 to 6 GHz;
1.16 to consider allocation of frequency bands above 71 GHz to the EES (passive) and RAS, taking into account Resolution COM5-1;
1.17 to consider possible worldwide allocations for the EES (passive) and SR (passive) services in the band 18.6 - 18.8 GHz taking into account the results of the ITU-R studies;
8.5 to consider possible extension of the allocation to the MSS (Earth-to-space) on a secondary basis in the band 14.0 - 14.5 GHz to cover aeronautical applications as stipulated in Resolution COM5-2;
8.7 consider provision of up to 6 MHz of frequency spectrum to the EES (active) in the band 420 - 470 in accordance with Resolution COM5-13;
8.8 consideration of changes to the allocations in Region 3 for the band 1350 - 1400 MHz to permit co-primary use by the fixed service;
2.2 Preliminary agenda WRC-01:
3.5 allocations on a worldwide basis for feeder links in bands around 1.4 GHz to the non-GSO MSS with service links operating below 1 GHz, taking into account the results of ITU-R studies conducted in response to Resolution COM5-15;
The CEPT FM Working Group discussed at its meeting in Tromso (8-12 September 1997) the harmonisation of frequency bands above 105 GHz. The radio astronomy and remote sensing needs were available at the meeting. Especially the remote sensing community did much effort to explain its needs since for this community until now the frequency allocation and protection issues were hardly coordinated. After a brief discussion of the input of the remote sensing community in which its needs at these frequencies were explained, Luxembourg stated that it felt strongly that the use of exclusive passive bands should be examined very carefully before the European Common Allocation (ECA) table was established in the bands above 105 GHz. They were of the view that much of the radio astronomy observations in these band could be carried out from stations beyond the Earth's atmosphere, for example on satellites, and some scientific satellites were already in operation or planned with this capability. They were particularly critical of the CRAF Handbook for Radio Astronomy (2nd edition) which was lacking in this respect. Also, due to the high atmospheric absorption experienced at these high frequencies it would appear to be feasible to share active and passive services.
The FM Working Group agreed to establish FM PT33, to study these issues. CRAF will participate in this project team.
The terms of reference for this project team are:
1. to collect information on justified needs for all services for spectrum above 105 GHz, taking recent and planned technological advances into account as well as socio-economic factors.
2. to produce a draft ECA table based on document FM(96)134 Rev.2 for the bands 105-300 GHz for further evaluation by FM Working Group at the September 1998 meeting (taking account of global frequency usages, allocations, frequency plans, etc.).
3. Ideally, participants should include representatives of CRAF, WMO, SE Working Group and potential users of the spectrum, but the PT should at least have close liaison with these bodies.
4. To produce a draft document with comments from FM Working Group on the CRAF Handbook for Radio Astronomy (2nd edition) regarding bands below and above 105 GHz.
5. To bear in mind that many allocations above 105 GHz are global.
6. The PT shall report to each FM meeting.
CRAF and the remote sensing community will collaborate to present a coherent opinion where required to protect passive frequency use for scientific applications.
The launch of Iridium satellites is proceeding rapidly at a rate of about 4 per month. However, the problem of the interference of transmissions of the Iridium downlink into radio astronomy observations is still not solved. In written documentation Motorola explains clearly that no protection of other users of radio is foreseen in the Iridium system (e.g. in J.J.Schuss et al., 1996, Proceedings of the IEEE International Symposium on Phased Array Systems and Technology, 15-18 October 1996, Boston, MA, p.411-415). Furthermore, recent studies on spurious emissions from satellite active antennas (to be used in the Iridium system) show that protection of radio astronomy is not achievable with an active antenna system: in such a system one cannot control unwanted emissions through the antenna sidelobes.
In the context of CEPT PT SE28 CRAF had many discussions with Motorola about this problem but the question remained unsettled until now (see Iridium). To overcome the deadlock in the discussions and the search for just solutions, CRAF invited Motorola to its 24th meeting. However, Motorola was not yet able to take part in this technical discussion about the sharing problem between radio astronomy and Iridium.
A major concern of the worldwide radio astronomy community and CRAF is the interpretation of Motorola/Iridium the ITU-R Radio Regulations footnote S5.372 which states: "Harmful interference shall not be caused to stations of the radio astronomy service using the band 1610.6 - 1613.8 MHz by stations of the radiodetermination-satellite and mobile-satellite services (No. 2904/S29.13 applies)". This footnote is given to MSS alocations within the band 1610.6 - 1613.8 MHz and adjacent band allocations to MSS. This question led to many discussions with Motorola and other operators about the issue on how to read a footnote. A major concern of CRAF is that if a service [in this case: radio astronomy] is regulatory protected and an application will cause harmful interference while it will not take proper precautions to protect another service ultimately the legal status of an international treaty as the ITU-R Radio Regulations becomes an issue. For that reason CRAF addresses below the issue of the interpretation of an ITU-R regulatory footnote, especially how Motorola representatives explained this to CRAF in various occasions.
A key question in the discussions is the interpretation of the footnote S5.372 (see above), particularly because of the downlink transmissions of the Iridium system at frequencies just above the radio astronomy band 1610.6 - 1613.8 MHz. Questions are, e.g. "What is the status of a secondary service with respect to a primary service?", "What is the status of a service with respect to a service in an adjacent band? - does this depend on the allocation status?".
The ITU-R Radio Regulations footnotes S5.28 - S5.30 state that:
S5.28 - Stations of a secondary service:
S5.29 [a] shall not cause harmful interference to stations of primary services to which frequencies are already assigned or to which frequencies may be assigned at a later date;
S5.30 [b] cannot claim protection from harmful interference from stations of a primary service to which frequencies are already assigned or may be assigned at a later date.
For a native English speaker, it seems plain that these footnotes mean that a station of a secondary service must not cause harmful interference to a primary service in any band. However, Motorola disputes this reading. In the various discussions between CRAF and Motorola the following formalized versions were noted:
1. Stations of a secondary service may cause harmful interference to stations of primary or permitted services allocated frequencies in other bands.
2. Stations of a secondary service are under no obligation not to cause harmful interference to stations of primary or permitted services allocated frequencies in other bands.
3. Stations of a primary service cannot claim protection from harmful interference from stations of a secondary service assigned frequencies in another band.
4. The status of primary, enjoyed by a service, confers on that service no general right to protection from interference from stations of services enjoying secondary status.
5. Stations of a secondary space service may cause harmful interference to stations of primary or permitted services allocated frequencies in other bands.
6. Stations of secondary services shall not cause harmful interference to stations of primary or permitted services to which frequencies are already assigned or to which frequencies may be assigne at a later date unless those services are allocated to another band.
All interpretations 1 through 6 were rejected by representatives of Motorola as not correctly representing Motorola's view.
7. A secondary service has the same obligations towards a primary service in another band as does a primary service.
A representative of a company associated with Iridium volunteered the remarkable alternative:
8. Any service, primary or secondary, is allowed to cause harmful interference to any other service allocated to another band.
But CRAF considers this statement is in conflict with the culture and tradition of the ITU as clearly expressed already in Article 1 of the Constitution of the ITU. However, this doctrine review shows that Motorola ignores the fact that footnote S5.372 is not only given for the band 1610.6 - 1613.8 MHz in which the Radio Astronomy Service has a primary allocation, but also for the bands 1610.0 - 1610.6 MHz and 1613.8 - 1626.5 MHz in which the Mobile-Satellite Service has a primary allocation for the Earth-to-space transmissions, while in the latter band it has a secondary allocation for the space-to-Earth transmissions. Clearly noted in the footnote S5.372 is that in the band 1610.6 - 1613.8 MHz radio astronomy enjoys the mentioned protection - full stop.
Teledesic proposed to construct, launch, and operate a constellation consisting of 840 satellites in non-geostationary satellite orbits. The constellation is organized into 21 circular orbit planes with each plane containing a minimum of 40 active satellites spaced evenly, and up to four operational spares per orbital plane. Additional spares will be constructed to replace failed satellites so that no orbital plane contains fewer than 40 operational satellites at any time. The system will begin initially with 288 satellites in 12 circular orbit planes. In this initial system each plane will contain 24 satellites (the Wall Street Journal, 19 February 1997).
The orbit planes are at a Sun-synchronous inclination, 98.2o, which keeps them at a constant angle relative to the Sun. These satellites will operate at an altitude between 695 and 700 kilometers and will communicate with earth stations operating above a 40o elevation angle. Teledesic requested use of paired spectrum in the 28.6 - 29.1 GHz (uplink) and 18.8 - 19.3 GHz (downlink) band segments for its service links, and the 27.6 - 28.4 GHz (uplink) and 17.8 - 18.6 GHz (downlink) band segments for its "gigalink" gateway terminals. Teledesic proposed to operate inter-satellite links in the 59.5 - 60.5 GHz and 62.5 - 63.5 GHz bands to interconnect each satellite with eight other satellites in the same and adjacent planes. This network will operate as a NGSO Fixed-Satellite Service system.
The Teledesic network proposed to offer a wide range of information services, from high-quality voice channels to broadband channels supporting videoconferencing, interactive multimedia, and real-time, two-way digital data. Teledesic proposed "bandwidth on demand," allowing users to adjust the channel's bandwidth to match traffic volumes and applications. Teledesic claimed that this flexibility reduces transmission costs, increases the efficiency of the transmission medium, and maximizes the overall capacity of the system.
The frequency plan for which Teledesic got an FCC-license is as follows - (see FCC Order and Authorization [March 14, 1997]):
|service links||18.8 - 19.3 GHz (down)||28.6 - 29.1 GHz (up)||primary|
|gigalinks||17.8 - 18.6 GHz (down)||27.6 - 28.4 GHz (up)||secondary|
|inter-satellite links||65 - 71 GHz|