CRAF Newsletter 1998/2

June 1998

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
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. The Chairman's Corner

The announcement that Italy is to build a new 64-m radio telescope in Sardinia is great news for European radio astronomy. It also reminds us of the challenge of identifying and protecting radio-quiet sites for future instruments. As the radio spectrum becomes ever more crowded the oases of passive frequency bands and radio-quiet sites are coming to seem like national parks which require political committment to maintain. Government policies often work against us unintentionally. Cuts in public spending and pressures from the telecommunications giants are leading to more deregulation of the radio spectrum and more auctions of radio frequency bands. In such a race only the rich can win. Radio astronomy will never command financial riches, so it will need to find other ways to achieve its goals. Public interest in astronomy is higher than it has ever been, fuelled by NASA press releases. Very often students are motivated to study physical sciences, primarily because they are struck by the results of astronomical research. Let us not miss this opportunity to tell more people what radio astronomers are doing and why it needs protection.

From this year our Newsletter appears in hardcopy, kindly published by the European Science Foundation. This should bring a wider readership and through these new readers a wider awareness of the interference issues facing radio astronomy. If you are receiving the newsletter for the first time have a quick look at the back page. There instead of sport you will find a list of the abbreviations used in this issue. This is a new feature which we hope will be helpful. A fuller list appears in the CRAF Handbook for Radio Astronomy, and is updated on the CRAF web pages.

R.J.Cohen - Jodrell Bank

2. CRAF Meeting 25 [2-3 April 1998]

The 25th CRAF meeting was held at the Max-Planck Institut für Radioastronomie in Bonn. The meeting was also attended by Dr.M.M.Davis, Chairman of the USA's NRC Committee on Radio Frequencies, CORF, who reported on CORF activities. The main items discussed during the meeting concern the progress of the licensing of the Iridium System in Europe, the work in CEPT project teams, and the preparations for the WRC-99 and -01.

* Licensing of the Iridium System in Europe:

The CEPT European Radiocommunication Committee, ERC, has concluded that a license to the Iridium System in Europe for downlink transmissions should include a condition guaranteeing the protection of radio astronomy in Europe. The Milestone Review Committee of the ERC, MRC, oversees this process. CRAF participates in ad-hoc MRC meetings together with Iridium LLC to reach an agreement to co-exist in the 1.6 GHz domain of the radio frequency spectrum (see section 4).

* CEPT project teams: CRAF participates actively in CEPT project teams dealing with
- spurious and out-of-band emissions (SE21)
- digital video broadcasting (SE27)
- sharing between the mobile-satellite service and other services around 1.6 GHz and below 1 GHz (SE28)
- frequency allocations above 71 GHz (PT33)
- high density fixed service applications (such as Sky Station) between 10.7 and 43.5 GHz (PT34)
(see section 6 for details)

* Preparations for the WRC-99 and -01: The preparations for the World Radiocommunication Conferences 1999 and 2001 are already in full swing. Both regulatory conferences have great importance for the radio astronomy service. Much preparatory work is done in project teams of the CEPT Working Group on Frequency Management, WG FM. CRAF participates actively in this work and is working on a coherent European position for each of the WRC agenda items. The CRAF position is developed in close cooperation with IUCAF.

CRAF also applied for Sector membership of the ITU Radiocommunication Sector, ITU-R.

The activities of the CRAF frequency manager are already under full steam. He plays a key role in the discussions with Iridium LLC and various European administrations about the Iridium issue.

3. 1st CRAF workshop

CRAF held its first workshop during January 26-28 at Nançay Radio Observatory. The subject for discussion was the x% issue: what is the percentage of time that radio astronomers can accept interference which is above the detrimental levels given in Recommendation ITU-R RA.769? Earlier studies within ITU-R Study Group 7 (and formerly 2) on Radio Astronomy recommended that a value of 10% be used in propagation calculations, to deal with variable propagation losses between a single radio telescope and a single terrestrial transmitter. The number of 10% was later seized on by the mobile satellite community and interpreted their own way, as the fraction of time which radio astronomers would tolerate harmful interference, for example from nearby mobile earth-stations transmitting to a satellite. If the percentage x% is to be used in this way then CRAF members unanimously consider that 10% is far too high. After three days of discussion and drafting the workshop produced a document for input to ITU-R WP7B (document 7B/14), and for further discussion within CRAF itself. The document was considered by the Working Party and carried over to the next meeting in September for further study, with the intention of producing a draft new recommendation when such studies are concluded.

4. Radio Astronomy in Europe and Iridium

At a global scale, radio astronomy faces the threat of interference from out-of-band emissions of the Iridium system for mobile communication by satellite.

In the USA, an agreement was reached on March 3rd, 1998, between the "National Astronomy and Ionosphere Center" at Arecibo and Iridium LLC. This means that at present only US radio astronomical institutes have accepted agreements with Iridium LLC. These agreements imply that radio astronomy observations without harmful interference from the out-of-band emissions of the downlink transmissions of the Iridium System are limited to low traffic hours during the night (i.e. 4-8 hours, depending on the location of the radio astronomy station).

In no other country in the world is there such an agreement (to CRAF's current knowledge).

The present situation in Europe is that discussions take place between CRAF and Iridium LLC under the umbrella of the ERC Milestone Review Committee, MRC. The framework of these discussions is the regulatory frame of the ITU-R Radio Regulations (in their full scope including footnotes and relevant recommendations).

The MRC adopted its MRC Recommendation #04 which serves a condition to be incorporated in a license to Iridium LLC to protect the Radio Astronomy Service in Europe. In summary, the conditions are:

- until 1 March 1999: the out-of-band emissions from the transmissions of the Iridium System shall be below the levels of detrimental interference given in ITU-R Recommendation RA769-1.
- from 1 January 2006: the out-of-band emissions from the transmissions of the Iridium System (space-to-Earth) into the radio astronomy band 1610.6-1613.8 MHz shall be below the levels of detrimental interference given in ITU-R Recommendation RA769-1.
- between 1 March 1999 and 1 January 2006: an agreement between CRAF and Iridium LLC should be reached on the levels of detrimental interference accepted for specific time windows. In case no agreement can be reached, the MRC will recommend by 1 March 1999 that Iridium meets:
(a) an interference level of -238 dB(Wm-2Hz-1) for a portion of the day to be determined, and
(b) an interference level between -238 dB(Wm-2Hz-1) and -215 dB(Wm-2Hz-1), to be determined, for the remaining portion of the day.

Iridium LLC has yet to accept the condition that from 1 January 2006, the out-of-band emissions from the transmissions of the Iridium System into the radio astronomy band 1610.6-1613.8 MHz shall be below the levels of detrimental interference given in ITU-R Recommendation RA769-1, i.e. -238 dB(Wm-2 Hz-1) for single dish telescopes. CRAF considers this condition as a major concession by European radio astronomers to Iridium LLC, since it may put restrictions on radio astronomy operations in Europe for the period 1 March 1999 - 1 January 2006 to enable the startup of the Iridium System.

During the discussion mentioned, it was explained by CRAF that the feasibility of the Iridium LLC proposal to implement a "blanker" to blank 50% of the 90 msec cycle time of the Iridium System needs further thorough investigation. Furthermore, such a blanker solution cannot be used for VLBI applications.

It should be noted that although ITU-R Recommendation RA769-1 gives some protection, when observing within 38o from the satellite the levels of detrimental interference as given in this ITU-R Recommendation are not sufficient: the interference will be tremendous in any case.

Recently, tests have been done at sites of the US National Radio Astronomy Observatory to determine the impact of transmissions of the Iridium System on radio astrononomy observations. For these tests filters were installed at the participating NRAO stations to avoid intermodulation products from the Iridium System during the tests. CRAF considers that this option needs further consideration to investigate whether it can be applied for standard 1.6 GHz operations elsewhere. It should be noted also that the system temperature of the radio astronomy receiver increases by about 10 K and that the filter has to operate at cryogenic temperatures. There are strong indications that this option degrades the quality of the radio astronomy observations significantly.

  • The evaluation of the test results by CRAF has not yet been completed. However, the tests show in any case, that the interference from the transmissions of the Iridium System on radio astronomy observation is at least as expected by CRAF: when the Iridium System is fully operational the 1610.6-1613.8 MHz radio astronomy window is closed. Furthermore, interference from the broadcast channels of the Iridium System mimics spectral line phenomena well above the levels of detrimental interference as given in ITU-R Recommendation RA769-1: this is desastrous for radio astronomy since the band 1610.6-1613.8 MHz is primarily used for spectral line research. Iridium LLC has indicated that it will try to improve this effect.

    During the discussions, CRAF remarked that it is difficult to understand why radio astronomers have to sacrifice because of the fact that the frequencies from which the interference originates are outside the radio astronomy band 1610.6-1613.8 MHz and that protection is guaranteed by ITU-R Radio Regulations footnote S5.372. The following table summarizes the concessions made by CRAF and by Iridium LLC:

    concession by CRAFcommentconcession by Iridium
    1. Recommendation ITU-R RA769-1currently state-of-the-art: achievable sensitivities give levels for harmful interference more than 30 dB (Wm-2Hz-1) lower than in ITU-R RA769-1none
    2. ITU-R RA769-1 levels for detrimental interference shall be obeyed from 1 January 2006to enable Iridium LLC to improve its system to state-of-the-art technological standards
    3. time sharing between 1 March 1999 and 1 January 2006to enable Iridium LLC to startup and evaluate its system, since the constellation of the Iridium System is already in place

    CRAF considers its concessions to Iridium LLC as major offers to be seen in the context of the culture of respectfully living together in the radio frequency domain in order to enable adequate technological progress. As an example of the way CRAF acts in this respect, the reader is referred to the collaboration between ESA(ESTEC), Oerlikon-Contraves and CRAF which resulted in the development of a filter to protect radio astronomy against interference from cloud radar systems currently planned to operate between 94.0-94.1 GHz, i.e. a frequency band which has not been allocated to radio astronomy yet. When the will exists to work together towards a solution, the technology can be found. CRAF regrets that Iridium LLC knowing the issue of the incompatibility of its applications with radio astronomy already before 1992, did not take this into account in proper design of its system nor did it want to cooperate with CRAF to find a technical solution.

    At present, no agreement between CRAF and Iridium LLC exists.

    Additional Note: Iridium flares 100 times brighter than Venus can be seen from your home. More information can be found from the Visual Satellite Observer's Home Page (VSOHP).

    5. ITU-R activities

  • WP7D

    Three working parties of ITU-R Study Group 7 (SG7, science services) met in Geneva between February 23rd and March 7th, 1998. In order to prepare this meeting, radioastronomers met at the Institut Radio Astronomie Millemétrique, IRAM, in Grenoble, over the enlarged preceding weekend. There we could discuss openly and friendly, and the result was an input document to WP7B/7D, dealing with allocations to radio astronomy above 71 GHz.

    The new chairman of ITU-R SG7, Robert Taylor (USA), had reorganized the work of SG7, taking into account that the next World Radiocommunication Conference will be extremely important for the science services in general, and for radio astronomy in particular. Therefore he had given WP7D the task of preparation of the next WRC for all of study group 7. Radio astronomy interests on longer time scales should be carried on in a subgroup of WP7B. Unfortunately, this change had not been discussed in sufficient detail. After some discussion at the beginning of the meeting weeks, responsibility for radio astronomy was given back to WP7D, together with WRC99 preparations for all of SG7. The disadvantage of this reorganization was a temporary uncertainty in document allocation ("WP7B|7D") and meeting schedule (WP7D officially met a week after WP7B, with two days overlap), but the advantage is that after the discussion the profile of the interest of the new chairman of SG7 is better known.

    During the last meeting, though, radio astronomy was discussed in a drafting group of WP7B, and documents relevant for WRC99, like the mm-astronomy paper from the Grenoble meeting were handed over to WP7D after discussion. The "x% of time" paper from the CRAF workshop (see section 3) was briefly introduced and carried over to the October meeting of WP7D as a working document.

    Another liaison statement was sent to WP8D, responsible for a recommendation on sharing the bands 1610.6-1613.8 MHz and 1660.0-1660.5 MHz with the Mobile-Satellite Service. Again co-operation was offered and three WP7D members were offered as members of a correspondence group (in Europe: K.Ruf), but so far none of them has been contacted by WP8D or WP8D members.

    A rapporteur to Task Group 1-5 (Unwanted Emissions) was nominated: H.C.Kahlmann (NL) and WP7B/D drafted a liaison statement to TG1-5 dealing with the statistics of spurious emissions of space stations in the non-geostationary orbit.

    The next WP7D meeting will be held from 28 September to 1 October, 1998, and all the above mentioned items plus some additional ones will be subject to further discussed during that meeting. It appears again necessary to have just before this meeting a preparatory meeting of radio astronomers only, since the working party meetings are more and more enriched by industry representatives, who make open discussions very difficult, if not impossible.

  • TG1-5

    Task Group 1-5 of the ITU-R continues the work of TG1-3, namely to study unwanted emissions. At the WRC97 the relevant Recommendation 66 has been revised and now, inter alia, the task of TG1-5 is to develop limits of spurious emissions for space services to be considered for inclusion into the Radio Regulations at WRC99. In order to come to agreeable spurious emission limits, TG1-5 wrote liaison statements to a number of ITU-R study groups and joint working parties, asking, in simple words, how much it would cost, if space services suppress their spurious emissions by 10 dB or more. Representatives of a number of space service operators tried very hard to boycot these liaison statements. In the end the chairman had to use all his power and authority to get these liaison statements approved and sent, noting the reservations of space service operators in the meeting report.

    Radioastronomers were in addition active in drafting a framework recommendation on the protection of vulnerable services, such as passive services and safety services.

    The next TG1-5 meeting is scheduled for the 2nd and 3rd week of July, 1998.

    K. Ruf - Bonn

    6. Radio astronomy issues in CEPT project teams

  • European Common Table of Frequency Allocations

    CRAF participated in the ERC WG FM drafting group on the European Common Table of Frequency Allocations, ECA, which will come into effect in 2008. A draft table of allocations is currently under consideration by CEPT administrations.

  • SE21 - Spurious Emissions

    The European study on spurious emission issues (parallel to the work done in ITU-R TG1-5) is in good shape. A critical issue is as in TG1-5 the definition of the boundary between "spurious" and "out-of-band" emissions. At present it is understood to be at +/- 250% of the bandwidth. SE21 concluded that this is not suited for narrow band and side band systems. The term "out-of-allocation emission" is still controversial. Some consider that the unwanted emissions outside the band allocated to a service should be below the requirements necessary to protect the services in the affected frequency bands. This opinion got strong opposition from industry.

    SE21 developed its own Monte-Carlo methodology with a lot of effort. This approach is strongly pushed by commercial people. CRAF expressed much concern because the radio astronomy interests were not yet addressed in the methodology: several precautions were not included. It is not yet known whether this will do harm.

  • SE27 - Terrestrial Digital Video Broadcasting

    Concerning the development towards digital video broadcasting, CRAF considers that one should be aware of the out-of-band and spurious emissions which are much different from those of analogue broadcasting. Furthermore, one should be aware of the definition questions: e.g. what is meant by "out-of-band", by "spurious" (see SE21 above)? What is meant by "bandwidth"?

  • SE28 - Sharing between MSS and other services in 1.6 GHz range and below 1 GHz

    SE28 met two times since the 24th CRAF meeting. The MSS downlink issue at 1.6 GHz is now dealt with under the Milestone Review Committee (section 4). The remaining agenda item relevant for CRAF on issues around 1.6 GHz is the progress in software development using the SE28 Monte Carlo methodology concerning uplinks.

    SE28 developed on the methodology to estimate separation zones around radio astronomy observatories to protect radio astronomy observations from harmful interference from mobile earth stations. CRAF insists that the detailed algorithms are also made available. This is a necessary prerequisite for independent software development and evaluation by CRAF. SE28 did not yet produce this.

    In the USA, fixed coordination distances around radio observatories are used (only for frequencies below 1613.8 MHz) according to the following FCC criteria:
    ~ 100 miles: around single dish telescopes
    ~ 30 miles: around VLBI stations.
    The FCC also demands positioning capability within the handset. This requirement does not hold for Motorola, since the Iridium System operates above 1621.35 MHz.

  • PT33 - Harmonisation of Bands above 105 GHz

    PT33 has to propose allocations for all services for frequencies above 105 GHz. The lower boundary was set by the upper frequency of the work of the Detailed Spectrum Investigation Phase I of the CEPT (DSI-I)

    The upper frequency boundary for the work of PT33 was not given by the CEPT. Given the agenda of WRC99 and the draft agenda for WRC01 (+ ideas for WRC03) the meeting decided to address all frequencies between 71 GHz and 1 THz:
    priority 1: 71 - 275 GHz (i.e. up to the highest frequency in the ITU-R Radio Regulations Table of allocations)
    priority 2: 275 - 400 GHz (i.e. up to the highest frequency mentioned in the ITU-R Radio Regulations)
    priority 3: 400 GHz - 1 THz.

    The work should be completed before September 1998 for the bands up to 300 GHz and before the end of the year for the whole range of frequencies.

    Only two services had developed concrete views: remote sensing (i.e. meteorology) and radio astronomy (e.g. the CRAF handbook was input to the meeting). Also NATO had indicated their frequency "wishes".

    PT33 noted the following for radio astronomy:
    [a] physics tells us that all frequencies in this frequency domain have radio astronomical interest.
    [b] given the variable tropospheric propagation conditions as a function of frequency sharing in higher frequency bands might be better feasible than at lower frequencies.
    [c] when we speak of sharing with active services, we make a distinction between terrestrial applications, and aeronautical and space applications: for the latter no allocation for downlinks should be made within or adjacent to a radio astronomy band. The criteria for space borne remote sensing are of course to some extent the opposite.
    [d] mm-wave observatories are usually located at high altitudes which also give parameters to be included in sharing conditions.

    The CRAF contribution to PT33 will rely on the conclusions of IUCAF mm-wave working group.

  • PT34 - High Density Fixed Service (10.7-43.5 GHz)

    CRAF participates in the work of this project team which has two main goals:
    [a] the preparation of agenda item 1.4 of the WRC99 (HDFS and the use of the band 40.5-42.5 GHz) and
    [b] the sharing problems between FS and FSS between 10.7 GHz and 43.5 GHz.

    The group reviewed all relevant frequency bands and decided to send a questionaire to administrations and international organizations to collect as much information as possible on planned FSS systems in the bands between 10.7 and 43.5 GHz.

    7. Unknown Space Station finally traced

    Since about 1992, radio observations done in the 322.0 - 328.6 MHz band suffer harmful interference from an unknown space station. The interference still exists at a level not different from its initial detection. In the frequency band 322.0 - 328.6 MHz the Fixed, Mobile and Radio Astronomy services enjoy a primary (shared) allocation.

    Radio astronomers in the Netherlands and India were the first to report the existence of this unknown space station of which several characteristics were derived from careful analysis of the radio astronomical measurements. The radio astronomy observations were confirmed by the Leeheim Satellite Monitoring Station of the German administration. The Dutch administration filed a formal complaint at the ITU in Geneva. The ITU brought this to the attention to of the USA, Russian and Chinese administrations.

    CRAF was informed by the Russian administration that it could not be a Russian space station. In the meantime the US administration (NTIA) and the spectrum manager of the US National Science Foundation, Dr.T.Gergely, put much effort into this issue attempting to solve it.

    At the 43rd meeting of the Committee on Radio Frequencies of the US National Research Council, CORF, in Washington (13-14 May 1998), Dr.Gergely reported that now the space station is known. For details, see: the TEX satellite. This space station has two important problems: [1] it transmits illegally at the frequency 328.25 MHz, and [2] it has no "OFF-switch" to kill the satellite's transmissions.

    Lessons have to be learned from this case to avoid similar cases in future. Today, the Radio Astronomy Service is the victim: tomorrow it could be a safety-of-life service.

    8. Abbreviations used in this Newsletter

    CEPT = Conference of European Post and Telecommunication administrations
    CPM = Conference Preparatory Meeting
    ECA = European Common Allocation
    ERC = European Radiocommunication Committee
    FCC = Federal Communications Commission (USA)
    FM = Frequency Management
    FS = Fixed Service
    FSS = Fixed-Satellite Service
    HDFS = High Density Fixed Service
    ITU = International Telecommunication Union
    ITU-R = ITU Radiocommunication Sector
    MRC = Milestone Review Committee
    NRAO = National Radio Astronomy Observatory (USA)
    NRC = National Rsearch Council (USA)
    NTIA = National Telecommunications and Information Administration (USA)
    PT** = Project Team
    SE = Spectrum Engineering
    SE** = SE project team
    TG** = Task Group
    VLBI = Very Long Baseline Interferometry
    WG = Working Group
    WMO = World Meteorological Organization
    WRC = World Radiocommunication Conference


    Last modified: July 8, 2004