CRAF Newsletter 2001/1

CRAF Newsletter 2001/1

June 2001

The European Science Foundation is an association of its 67 member research councils and academies in 24 countries. The ESF brings European scientists together to work on topics of common concern, toco-ordinate the use of expensive facilities, and to discover and define new endeavors that will benefit from a co-operative approach
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.


1. Chairman's Corner

When writing my first Chairman's Corner for this Newsletter, I had a look at the first Corner written by my predecessor, Dr. R.J. Cohen, in January 1996. The issues mentioned at that time still sound very familiar to the radio astronomers engaged in "keeping our windows clean". In fact, two of the key themes of yore, the necessity of adhering to the Recommendation ITU-R RA.769 levels for interference into radio astronomy bands and the adequate protection from out-of-band emissions of satellites into our bands, were discussed with the same gusto during the recent Task Group 1-7 meeting in Maastricht as they were during the Task Group 1-3 meetings years ago.

This does not come as a surprise, as the basic positions of the various groups of spectrum users involved in these issues have not really changed over the years. For us radio astronomers, the bottom line remains preserving our capability to observe the Universe at those radio frequencies we need for scientific research, at the sensitivity levels we require. The attitude towards our requirements from other spectrum users with whom we seek to coexist ranges from friendly, through indifferent to outright hostile. Commercial pressure has failed to crush radio astronomy, though, and we will keep up the fight for our rights.

To keep up the good fight within Europe, CRAF members from 17 countries participate actively in meetings at local, national and European level. At a worldwide level, CRAF can operate either directly as a Sector Member of the ITU Radiocommunication Sector or through those members who are also members of IUCAF, the sole worldwide organisation of radio astronomers. The united front we are able to form as European radio astronomers through CRAF has proved to be of great importance, as well as our freedom as an ESF Experts Committee to determine our common position.

Wim van Driel - Paris Observatory

2. Report of 32nd CRAF meeting (19-20 April 2001)

The 32st CRAF meeting was held on 19-20 April 2001 in Sweden, at the Onsala Space Observatory, Onsala, and the Microwave Technology Laboratory of the Chalmers University in Göteborg.

The main items discussed were the developments on some WRC-03 agenda items, the development of mobile satellite systems at 1.6 GHz, a CRAF position on some specific issues, ultra-wide-band transmissions, the conclusion of the evaluation of the SE28 Monte Carlo coordination software and a description of the CRAF EMI and spectrum occupancy database facilities. The CEPT ERC was represented by Mr.S.Ritchie of the Irish administration.

On the different issues:

  • WRC-03: the agenda item 1.16 on feeder links adjacent to the band 1400-1427 MHz is a key issue for CRAF in the preparations for the WRC-03. The interpretation and the application of footnote S5.340 which says that all emissions are prohibited in this band is subject to discussion within various administrations.
  • Mobile Satellite Service, MSS, at 1.6 GHz:
    The Iridium satellite system resumed commercially operations in March 2001. Noting the concerns of CRAF, the CEPT has written to the new operator explaining that in Europe it must comply with the CEPT ERC recommendations and the conditions defined in the Agreements between the ESF and Iridium LLC.
    Discussions on the European standard for aeronautical earth stations in the band 1610.6-1613.8 MHz are continuing, as well as work on the coordination of GLOBALSTAR mobile earth stations at 1.6 GHz.
  • CRAF defined its position on some key parameters in the discussions on various WRC-03 agenda items.
  • Ultra-Wide Band, or UWB, transmissions are potentially a great danger for many radiocommunication services, including radio astronomy. ETSI is working on a European standard for UWB devices and CRAF is working within CEPT on the definition of conditions for UWB applications.
  • CRAF has adopted a users' guide for the 'SE28-Monte Carlo methodology and software'. It was shown that a statistical approach in coordination issues lead to results that are not significantly different from those derived by a deterministic method.
  • CRAF adopted a description of the CRAF facilities for an EMI and spectrum occupancy database. CRAF will develop a procedure for the participating observatories to communicate their EMI and spectrum occupancy data.

    3. IUCAF Workshop on RFI Mitigation (28-30 March 2001)

    In the ever more crowded radio spectrum, interference is now considered an unavoidable accident, and as in daily life, the best defence against accidents is self defence: try to make yourself immune to RFI, since the regulatory process will provide you with only basic protection.

    Radio astronomers are spectrum users, along with people who use TV, mobile phones, radar, etc, but there are strong differences. For example it is useless to tune a TV to a channel where there is no broadcast transmitter operating, whereas all the electromagnetic spectrum is of interest to astronomers, and may be used to receive marvellous pictures, in principle. In many channels the emission from cosmic sources is buried under man-made signals. Modern signal processing techniques seem to offer great potential to separate out the weak cosmic signals from the roar of man-made noise.

    In the current regulatory environment, which seems to have moved from the concept of absolute to relative protections, radio astronomers are encouraged to apply mitigation techniques, in order to facilitate sharing and the development of new radio services. It is not always clear, however, what "mitigation" means. It may mean simply more accurate modelling, for example to take account of terrain loss or blocking by known obstacles in a propagation path. Or it may encompass the sophisticated signal-processing techniques and algorithms referred to above, which enable radio astronomers to detect highly red-shifted hydrogen line emission in the middle of the 0.9-GHz GSM band in a geographical area with excellent GSM coverage. Clearly, mitigation techniques are very important, however ill-defined.

    In order to promote the use of mitigation techniques and to improve understanding of the term "mitigation", IUCAF organized a 3-day Workshop on Interference Mitigation. The meeting was co-sponsored by the International Astronomical Union (IAU), the European Infrastructure Cooperation Network (ICN, also referred to in jest as the interference cancellation network), and the Max-Planck-Institut fur Radioastronomie, which hosted the workshop in Bonn. One new approach of the workshop was to bring together two separate communities: engineers and frequency managers, who each deal with mitigation in different ways. Another aim of the workshop was to make an inventory, as complete as possible, of what is going on in both communities world-wide.

    All continents except Africa were represented among the 50 participants. The 3 days were filled with more than 40 presentations, ranging from short communications to extensive review talks. High priority was given to discussions, and on the final afternoon preliminary conclusions were drawn. There was wide agreement that mitigation techniques may open opportunities for observations in frequency bands where radio astronomy has no allocation. Additionally, a range of measures can be taken to fight interference from active services in radio astronomy bands; however it was emphasized by several speakers that even the most sophisticated and fully-developed mitigation tools will never be a replacement for unpolluted passive frequency bands.

    The following example illustrates the point. Our Australian colleagues have been experimenting with algorithms to elimate interference from observed data. Through their ingenious techniques they unintentionally elimated pulsar signals from the data as well. More generally, in trying to separate cosmic signals from man-made ones, one unavoidably must make assumptions about the expected signals. This automatically limits our ability to make new, unexpected and surprising discoveries in our research. If radio astronomy had been forced to apply such mitigation techniques for the last 40 years, then today we would perhaps not know of the existence of pulsars or neutron stars, and black holes would be considered as meaningless singularities in Einstein's field equations.

    At the end of the meeting the participants had a far better appreciation of the difficulties and achievements in both the technical and frequency management fields, and they understood the need and the value of continuing to develop the links which had been forged in this workshop.

    Klaus Ruf
    Max-Planck-Institut fur Radioastronomie

    4. Establishing radio-quiet zones

    Adequate protection of a radio astronomy site usually implies that a radio-quiet zone is established around the station. For many radio observatories all over the world, such provisions have been made, while in other cases work is in progress to find adequate coordination zones. The establishment of such a zone is usually done by the local Administration in consultation with the radio astronomy station to which it applies, taking into account the national legislation and the administrative structure of the country where the station is situated.

    Recently, such discussions took place in Poland and Spain, to establish proper radio-quiet zones for the stations at Torun and Yebes, respectively.


    The Torun Radio Astronomy Observatory is located in the village Piwnice about 12 km north of the city of Torun in central Poland.
    The current discussions with the Lysomice parish and the Kujawy and Pomorze self-government are likely to result in a radio-quiet zone with a radius of a few km around the obervatory. A new development plan for the Province will be worked out soon. Torun Radio Astronomy Observatory has already submitted a proposal for a radio-quiet zone around the observatory in Piwnice to be included in this plan. Although the radio-quiet zone in Piwnice is not formally esablished yet, the current practice is that the observatory is always consulted when new radio transmitters are to be installed in the neighbouring area. Also any changes to the development plan for Piwnice and nearest villages must be approved by the observatory.
    Part of the land around the 32-m antenna, which is also an element in the European VLBI network, is private. Since the erection of new houses is now stopped, the farmers are demanding indemnification for loss of possible further development of their farms. In addition, it is worth noting that there is a large demand on the development of building industry in the suburbs of Torun. All these facts make the establishment of the radio-quiet zone in Piwnice a difficult and complex task.


    The Centro Astronómico de Yebes is situated in the province Guadalajara at a distance of about 50 km north-east of Madrid.
    Although the discussions are not yet completed, it seems likely that the Spanish Administration (i.e. the Secretaria de Estado de Telecomunicaciones y para la Sociedad de la Informacion in Madrid) will agree to a radio-quiet zone around Yebes of 1 km. This is similar in extent to the quiet zones for many other observatories. In addition, it is considered to establish an area around the station where the Spanish Administration will place restrictions on transmitting stations to protect the radio astronomy site. These restrictions are rather detailed and vary with frequency following the levels harmful for continuum observations from ITU-R Recommendation RA.769 for the frequency range 1.4 - 92 GHz.

    5. Digital broadcasting

    Terrestrial Digital Audio Broadcasting - T-DAB

    Meeting in Wiesbaden in July 1995, the CEPT adopted special arrangements relating to the use of the bands 47-68 MHz, 87.5-108 MHz, 174-230 MHz, 230-240 MHz and 1452-1492 MHz for the introduction of Terrestrial Digital Audio Broadcasting, T-DAB. Administrations who have approved or acceded to this arrangement will adopt the mentioned bands for their T-DAB stations. CRAF members in many countries are involved in local discussions with their national administrations on optimizating the channel plan to protect radio astronomy stations operating in the band 1400-1427 MHz.

    Terrestrial Digital Video Broadcasting - DVB-T

    In Chester in July 1997, the CEPT adopted a Multilateral Coordination Agreement relating to the introduction of Terrestrial Digital Video Broadcasting, DVB-T. The frequency bands involved are 174-230 MHz and 470-862 MHz. In the latter frequency range, the band 608-614 MHz is used by radio astronomy observatories in Belgium, France, Germany, Italy, the Netherlands, Poland and the United Kingdom.
    In several European countries the band 608-614 MHz, i.e. channel 38 in the Stockholm 1961 Plan, is considered attractive for DVB-T tests. Consultation with some administrations resulted in adjustment of these test-plans in order to protect radio astronomy operations in this band.

    Revision of the Stockholm 1961 Plan

    The coordination of video broadcasting in the broadcasting bands IV (470-582 MHz), and V (582-960 MHz) and audio broadcasting in the bands I (41-68 MHz), II (87.5-100 MHz), and III (162-230 MHz) is regulated by the Stockholm Agreement 1961 (updated for FM in Geneva, 1984).
    Considering that the change from analogue to digital technology implies different spectral requirements, an ITU-R Regional Radiocommunication Conference, RRC, for a revision of the Stockholm Agreement 1961 will be held, to completely replan the bands 174-230 MHz and 470-862 MHz envisaged for digital broadcasting (both video and sound broadcasting). This conference will take place in two sessions of about 2 weeks in 2003 and about 5 weeks in 2005, respectively (details to be decided by the ITU-Council). The conference will handle the issue for the European Broadcasting Area, while considering also participation from the African Broadcasting Area. Whether the conference will start the planning work from scratch or from the Stockholm 1961 Plan, is still subject to consideration.

    T-DAB/S-DAB planning

    Separate from the RRC on digital broadcasting planning, an extraordinary WG FM meeting will be held on June 10-18 2002 in the Netherlands for plan 7 additional T-DAB blocks in the frequency range 1467.5-1492 MHz.

    These developments in the Broadcasting Service may not have any impact on the Radio Astronomy Service. Nevertheless, we should monitor the developments carefully to protect the European radio astronomy interests in the frequency areas considered, particularly the band 608-614 MHz.

    6. WRC-03 agenda item 1.15


    WRC-2003 agenda item 1.15: to review the results of studies concerning the Radionavigation-Satellite Service, RNSS, in accordance with Resolutions 604 (WRC-2000), 605 (WRC-2000) and 606 (WRC-2000).


    WRC-2000 allocated the bands 1164 - 1215 MHz, 1260 - 1300 MHz and 5010 - 5030 MHz to the RNSS (space-to-Earth) (space-to-space) in accordance with Resolutions 604, 605 and 606 (WRC-2000). These new allocations are considered essential for the development and enhancement of new and existing RNSS systems like GALILEO, GPS and GLONASS.
    The European Union initiated the development of a second-generation European radionavigation-satellite system, Galileo. It is being designed as an independent, global, civil-controlled system which will be used, together with other RNSS systems, as a key element of the second-generation global navigation-satellite system, GNSS-2. Galileo will provide open access and controlled access services, including reliable signals for safety-of-life applications, such as civil aviation and maritime transport.

    Band 1164 - 1215 MHz (Res 605)

    In the band 1164 - 1215 MHz a provisional pfd-limit has been introduced for the protection of the Aeronautical Radionavigation Service, ARNS, systems operating in this band. The need for and the value of this provisional limit are to be verified at WRC-03 in accordance with Res 605 (WRC-2000). The protection of the distance measuring equipment, DME, and TACAN, tactical air navigation systems operating in this band is essential for the safety of air traffic. This spectrum is part of the 960-1215 MHz band which is allocated to the Aeronautical Radionavigation Service.
    The pfd-limit set during WRC-2000 was based on several assumptions concerning the protection ratio of DME from RNSS signals, the airborne DME antenna discrimination towards RNSS satellites, and the apportionment of interference sources. All these assumptions were to be confirmed, using measurements as well as simulations. The provisional pfd-limit is valid for the aggregate interference from all RNSS systems. The derivation of single-entry limits for each RNSS system is also to be investigated in time for WRC-2003.

    Band 1215 - 1300 MHz (Res 606)

    At WRC-2000, the CEPT proposed to introduce a pfd-limit in the band 1215 - 1300 MHz, with a value of -133 dBW/m2/MHz per satellite. Due to the strong opposition of the US and Russia to have any pfd-limit in the band 1215 - 1260 MHz already used by GPS and GLONASS, Resolution 606 (WRC 2000) was approved calling for the necessary studies to assess the need for and the value of the pfd-limit in the band 1215 - 1300 MHz to protect the Radionavigation and Radiolocation Services, RNS and RLS, respectively.
    In addition to the RNSS, these bands are allocated by footnote S5.331 to the Radionavigation Service, RNS, in several countries on a primary basis. According to S5.282, the amateur-satellite service (Earth-to-space) may operate in the band 1260-1270 MHz subject to not causing harmful interference to other services operating in accordance with the table (see S5.43).

    Band 5010 - 5030 MHz (Res 604)

    This aspect of this agenda item is very important for radio astronomy as was already indicated before WRC-2000 (see Newsletter 2000-1). WRC-2000 allocated the band 5010 - 5030 MHz on a primary basis to RNSS for transmissions space-to-Earth, i.e. adjacent to the band 4990-5000 MHz allocated on a primary basis to radio astronomy.
    To protect the radio astronomy service below 5 000 MHz a provisional pfd-limit, that applies to out-of-band emissions from RNSS systems operating in the band 5 010-5 030 MHz falling into the radio astronomy band 4 990-5 000 MHz was approved by WRC-2000 in accordance with Resolution 604 (WRC-2000). Due to the ongoing studies the pfd-limit for the RNSS is subject to revision at WRC-03.
    The general problem of protection of radio astronomy and passive services is under study in ITU-R, inter alia, in response to Recommendation 66. In this respect, TG1/7 has been recently created to answer to WRC-2003 agenda item 1.8.2, i.e. the protection of passive services from space stations (transmitting space-to-Earth). In support of such activity, WP4A and WP7D have undertaken studies on the application of the epfd concept to the protection of radio astronomy and WP7D has indicated that the provisional pfd-limit would be likely to be modified accordingly. The results of this work should be applied to the RNSS emissions into the band 4990 - 5000 MHz. Within the CEPT, WRC-03 Agenda Item 1.8.2 is handled by project team SE21.
    CRAF participates actively in these discussions.

    7. Abbreviations used in this Newsletter

    ARNS = Aeronautical Radionavigation Service
    CEPT = Conference of European Post and Telecommunication administrations
    CRAF = Committee on Radio Astronomy Frequencies (ESF)
    DME = Distance Measuring Equipment
    DVB-T = Terrestrial Digital Video Broadcasting
    EMI = Electromagnetic Interference
    epfd = Equivalent Power Flux Density
    ERC = European Radiocommunications Committee (CEPT)
    ESF = European Science Foundation
    ETSI = European Telecommunication Standardization Institute
    FM = Frequency Modulation
    GLONASS = GLobal NAvigation Satellite System
    GNSS = Global Navigation Satellite System
    GPS = Global Positioning System
    GSM = Global System for Mobile Communication
    IAU = International Astronomical Union
    ICN = European Infrastructure Cooperation Network
    ITU = International Telecommunication Union
    ITU-R = International Telecommunication Union - Radiocommunication Sector
    IUCAF = Scientific Committee on the Allocation of Frequencies for Radio Astronomy and Space Science
    MSS = Mobile-Satellite Service
    pfd = Power Flux Density
    RLS = Radiolocation Service
    RNS = Radionavigation Service
    RNSS = Radionavigation-Satellite Service
    RRC = Regional Radiocommunication Conference (ITU)
    SE = Spectrum Engineering (CEPT)
    S-DAB = Satellite Digital Audio Broadcasting
    T-DAB = Terrestrial Digital Audio Broadcasting
    TG = Task Group (ITU-R)
    TV = Television
    UWB = Ultra-Wide Band
    VLBI = Very Long Baseline Interferometry
    WG = Working Group
    WP = Working Party
    WRC = World Radiocommunication Conference (ITU-R)


    Last modified: June 19, 2001; revised: July 13, 2001