CRAF Newsletter 1996/1

January 1996

The European Science Foundation is an association of its 62 member research councils and acedemies 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.

Important notice: The CRAF clearing house got new telephone and fax numbers: The telephone number is (+31)521-595100, the fax number is (+31)521-597332


1. The Chairman's Corner

At the start of 1996 radio astronomers may be tempted to look back comfortably on the gains which they made at WRC-95. The 6.668 GHz line of methanol which had the misfortune to be discovered only in 1991 has now received recognition in the Radio Regulations though a new footnote. Many of our established frequency bands also received footnotes to provide protection against out-of-band emissions from satellites. These footnotes contain direct reference to ITU-R RA Recommendation 769, which specifies the interference thresholds. Gone are the days when these protection criteria for radio astronomy were hidden in Report 224 of the CCIR. They are now referred to directly in the Radio Regulations.

But it would be wrong to think that "the system" will now take care of us. The threat from satellites and their unwanted emissions is actually stronger than before, in some quarters. Iridium is due for launch at the end of this year. Motorola propose to operate in the secondary downlink band 1610-1626.5 MHz allocated at WARC-92. Footnote 733E is there to protect us against the downlink, including its unwanted emissions. But what does the protection mean in practice? Motorola admit that the unwanted emissions are likely to exceed the interference thresholds for radio astronomy most of the time. But this is not harmful interference they say, this is friendly interference. Motorola have a Memorandum of Understanding with radio astronomers of the US National Radio Astronomy Observatories. Motorola will let them observe by kindly providing them with an interface so they can blank their detectors or receivers during the pulsed downlink transmissions. The lucky radio astronomers will then be able to "see through" the picket fence of friendly interference. Is this what we would like in Europe? Would we be ungrateful enough to refuse? After all, ours is only a primary allocation, whereas the friendly interference would be from the unwanted emissions of a downlink with a secondary allocation. How simple it might be if we could just listen to the dollars talking, and forget the stars.

Radio astronomers have a fight on their hands. If this goes through, other satellite operators will see the benefits of being friendly too. That alone would take out many of our frequency bands. And you can bet that satellite operators wouldn't be our only friends on such terms. We must fight for the rights of our science to coexist alongside the multinational corporations.

R.J.Cohen - Jodrell Bank

2. New CRAF chairman

The chairman H.C.Kahlmann (Westerbork Radio Observatory) resigned in 1995 at the 19th CRAF meeting. He has been succeeded by R.J.Cohen (Jodrell Bank).

3. CRAF Meeting 19 [28-29 September 1995]

The main subjects discussed at the meeting concerned the World Radiocommunications Conference WRC-95, the increasing threat of interference from MSS Low Earth Orbiting satellites using frequency bands near bands allocated to the Radio Astronomy Service and the protection of mm-astronomy.

The agenda of the WRC-95 contains as major items the consideration of the report of the ITU Volutary Group of Experts, VGE, implying a complete revision of the Radio Regulations proposed by the VGE in its efforts to simplify these Regulations. Also high on the agenda are important matters related to the Mobile Satellite Service, MSS, and associated feeder links including the review of those provisions in the Radio Regulations which might hinder the timely introduction of new mobile satellite services. Attention is to be paid, however, to the existing services to which the frequency bands to be considered by WRC-95 are also allocated.

The VGE proposal does not seem to have much impact on radio astronomy. In the proposed harmonization and simplification of the Radio Regulations the Radio Astronomy Service is retained but the large amount of footnotes is simplified and combined to only a few footnotes.

The MSS allocations concern the frequency bands 149-150.05 MHz and 401-404 MHz. Satellite transmissions in these bands may cause significant interference by out-of-band emission in the RAS bands 150.05-153 MHz, 322.0-328.6 MHz and 406.1-410.0 MHz (see also section WRC 1995).

The protection of mm-astronomy is becoming an issue of concern. New cloud radar systems and vehicular radar may cause significant interference from harmonics of the transmitted signals at frequencies above 200 GHz. CRAF is preparing a document on this topic (which will be included in the 2nd edition of the see CRAF Handbook for Radio Astronomy as well). On the other hand, CRAF is in good contact with the manufacturer and operator of a new to develop cloud radar system section on (see vehicular radar).

The presure by satellite operators on the Radio Astronomy Service in the 1.6 GHz frequency area is extremely high. Motorola is approaching radio observatories to obtain a memorandum of understanding concering the coexistence of radio astronomical observations and MSS operations. INMARSAT attempts to reach its goal by "plain infiltration" in the radio astronomical community (see also sections on IRIDIUM MoU and CEPT SE28).

Pricing the spectrum has become an important issue and the developments have to be monitored carefully. In Europe there is yet no harmonization on this subject. The threat for French radio astronomy that also radio observatories would have to pay for spectrum use, has gone (hopefully for ever): a study to spectral pricing came to a result strongly opposed to this pricing.

4. CRAF Handbook for Radio Astronomy

The CRAF Handbook for Radio Astronomy has been published by the European Science Foundation in September 1995. It is distributed by the clearing house. Its readers are expected to be found primarily among frequency managers, administration and related bodies (such as ITU, CEPT). A 2nd edition will be published within about 1.5 years and will contain a.o. the following additional items:

The time to prepare the first edition of the handbook was relatively short (about 6 months effectively) because of questions from administrative bodies which had to be answered on short notice.

The ESF press release on the CRAF Handbook for Radio Astronomy had a tremendous effect. In many publications (journals, newspapers) and radio programs (interviews with Kahlmann and Cohen) attention was paid to this publication. There is obviously a lot of public interest and sympathy.

Until now, more than 300 copies of the book have been distributed by the clearing house, while the ESF distributed it among its relations as well. The reactions on the book have been very positive so far: from the ITU several suggestions for the 2nd edition have already been made.

5. Major activities


CRAF discussed with the Société Européenne de Satellite in Luxembourg (operating the GDL-6/ASTRA-1D satellite) about the interference Effelsberg experiences within the 10.6-10.7 GHz band from the ASTRA broadcasting satellite (TV). The ASTRA operator confirmed the validity of the complaint by the Radio Astronomy Service. By means of tests using a satellite simulator the company found that the FM uplink signals have a spectrum error after spectrum regeneration to ~10 GHz. The plan is a modification by the ASTRA operator of the uplink spectrum to improve the spectrum at 10.7 GHz. The ASTRA operators also told that if the solution cannot be made good enough they had to switch off their transponder, but that would be the very last option.


CRAF corresponded with the Italian companies Alenia Spazio and Elsag Bailey on GLOBALSTAR. CRAF asked for confirmation that the technical means are provided so that the levels of harmful interference to the Radio Astronomy Service as given in ITU-R RA769 and according to the allocations by the ITU in the bands possibly affected by GLOBALSTAR are not exceeded. In their reply it is stated that "GLOBALSTAR is well aware of the Radio Astronomy bands and the protection limits required in them, both from the ITU and the FCC point of view. We have designed our satellites, gateways and MESs to meet the requirements. In operation, we will ensure that no MES using the radio astronomy band in the 1610-1613.8 MHz range comes close enough to a radio astronomy station to cause interference". GLOBALSTAR indicates that it recommends a discussion concerning MSS/RAS co-frequency operations on a temporal basis (i.e. during periods of radio astronomy observations only) and not on a permanent basis, within the geographic protection zones.

5.3 MSS - RAS

In the process of the evaluation of the ERO Detailed Spectrum Investigation - Phase II, CRAF had expressed its concerns on the use of frequency bands near and adjacent to radio astronomy bands by little LEOs to the European Radiocommunications Office (Copenhagen). The report of DSI - phase II does not mention nor hint to this problem.

5.4 Vehicular radar at 76-77 GHz

The topic of vehicular radar has been brought to the attention of CRAF by CORF. The allocation for vehicular radar devices is in the 76-77 GHz band. In the US there is not yet an allocation, but it will probably also end up being 76-77 GHz for compatibiltiy reasons. It should be noticed that the 3rd harmonic of the 76-77 GHz falls directly within the 220 GHz primary passive allocation (CO lines). Stringent spurious emission limits are therefore required in order that the radars do not interfere with 220 GHz CO observations. The manufactorers told A.Clegg (US Federal spectrum management) that "the European astronomers told them that there are no radio observatories in Europe that observe at 220 GHz, so they would not be affected. CRAF informed CORF that this is not correct and explained the European situation.

In fact, the frequency of the 3rd harmonic (228-231 GHz) is one of the most frequently observed both at Pico Veleta and Plateau de Bure. The CO transition (2-1) being at 230 GHz. In addition this is almost exactly the band allocated to radio astronomy for continuum observations. There are many continuum observations made in this band with bolometer arrays for which the interference levels are about 20 dB more severe. So there is certainly the possibility of interference.

At Pico Veleta there is a road at 1-3 km distance which has a clear line of sight and is very popular with tourists (at least in the summer). This is the "highest road in Europe" and is an increasingly popular tourist attraction. Plateau de Bure is perhaps better protected, although to the south there is a line of sight to Sisteron at about 50 km - with additional attenuation of 34 dB + 50*0.05 dB = 36.5 dB to be applied to the numbers given by GM. Neglected is then any protection given by the radiation pattern of the radar in the vertical direction since the Plateau only subtends about 2.5 degrees at Sisteron. On that basis the interference from one car would still be 3.5 dB above the spectral line harmful limit of -197 dB/m2/Hz (ITU-R RA 769) for General Motors' proposed permissible spurious level at 1 km distance, assuming clear line of sight to the observatory's 0 dB sidelobe, one radar-equipped car and 0.05 dB/km absorption. Sisteron is at present the end of an autoroute, but this autoroute (A51) will probably be extended across the Alpes through Grenoble to become one of the main N-S routes in Europe. Construction work has already begun, although the ecologists have legal cases pending and are blocking some of the sites. Hence we can expect an intense traffic at Sisteron in a few years with interference levels many dB above the limit for spectroscopy.

According to CRAF the radars should be filtered by at least 40 dB more than currently envisaged. Even this may not suffice for the continuum observations which may require 20 dB more protection. So 60 dB may be a more correct estimate of the protection needed in the 1 mm band.

6. Policy

6.1 Motorola: IRIDIUM Memorandum of Understanding

Motorola has approached several key people at various observatories about the interference from the Iridium system in the protected 1612 MHz RAS band. Iridium with its downlink in the 1620 - 1626.5 MHz band [in Europe the band 1616 - 1626.5 is planned for both up- and downlink] is unable to reach the RAS harmful spfd levels as described in ITU.R-R.769. The purpose of these Motorola contacts is to discuss the predicted time periods Iridium cannot reach the RAS harmful limits at each observatory site and to draw up a Memorandum of Understanding. The modelling that Motorola has done for each site is based on traffic models for nearby metroplitan areas with a 1.5 safety factor.

In return for accepting the interference for 50 percent of the time, Motorola would provide a receiver system that would be able to serve as a clocking device for stopping the correlator during the 90 ms that Iridium uses the band as a downlink. This system could be supplied to each observatory in the form of a "study grant".

Motorola has recently visited Australia, Canada and Jodrell Bank. Visits to Arecibo and to The Netherlands, Germany, and Sweden are also in planning stages. The only existing MoU is with NRAO which had been signed on June 12th, 1994. No other observatory has signed.

MSS (uplink) has a primary allocation shared with RAS in the band 1610.6 - 1613.8 MHz [MSS has a primary allocation for the uplink in the band 1610 - 1626.5 MHz], while the MSS downlink has a secondary allocation in the band 1613.8 - 1626.5 MHz. Also FN733E holds. Shortly before WARC92 Motorola approached radio astronomy observatories for a memorandum of understanding (MoU). Calculations done for Jodrell Bank show that during about 4 hours in the night the interference would be below -240 dB W m-2 Hz-1. Else it is at least about -210 dB W m-2 Hz-1, being similar to the GLONASS interference. Any spectrum at 1612 MHz would show spurious features of a few tenths of a Kelvin. The MoU proposed by Motorola to Jodrell Bank is similar to the one signed by NRAO. If accepted the best situation would be a window of about 4 hours in the night during which sensitive radio astronomical observations can be done.

CRAF members have unanimously rejected the proposal for such a MoU in Europe.

6.2 EMI at 328.2 MHz

Westerbork and the GMRT suffer from interference at 328.2 MHz (i.e. within the radio astronomy band of 322.0 - 328.6 MHz) which comes very likely from a satellite. This identification is based on the interval of appearing/disappearing of the interference and spectral behavior (including doppler shifts). NFRA/CRAF asked the Dutch administration to submit a request to the German administration for monitoring assistence of the German station Leeheim. At present no results are available yet.

6.3 HiFi from space

According to the Washington Post (11 September 1995, p.27) there comes a possible threat in the S-band just above the VLBI band presumably for the frequency range 2310 - 2360 MHz. This may cause severe out-of-band emission affecting VLBI observations. The FCC is requesting a license to 3 commercial firms to orbit and operate satellites with commercial S band radio broadcasts from orbit. One company wants to offer 50 channels, which implies some considerable expanse of bandwidth. The intention is to receive these transmissions from car radios.

CRAF will investigate this development and aim for clarification.

7. WRC 1995

The WRC95 took place from 23 October to 17 November 1995 in Geneva. The most important agenda items were:

  1. The recommendations of he VGE report to simplify the Radio Regulations (VGE = Voluntary Group of Experts)
  2. New allocations to the Mobile Satellite Service (MSS), including feeder links.
CRAF members present were: Stanislaw Gorgolewski (Polish delegation, part time) and Klaus Ruf (German delegation, full time).

Radio astronomy could achieve some improvements, even though not on the agenda, in the form of "consequential changes". It almost appeared that protection of radio astronomy was the least controversial topic of the conference. Of course, new allocations to the Radio Astronomy Service could not be made, as this would be a substantial change the the table of frequency allocations, which must be put onto the agenda years before the conference. But protection of radio astronomy reached a new quality, as in several footnotes up to 15 GHz the detrimental effect of unwanted out-of-band emissions of satellite transmitters is pointed out.

In detail the results are:

  1. All MSS (space-to-Earth) allocations below 1 GHz get a footnote (S5.208A), saying that Radio astronomy in the bands below 1 GHz has to be protected from out-of-band emissions. ITU-R recommendation 769 is given as a source of information about interference levels.
  2. The MSS (space-to-Earth) allocation in the band 2483.5 - 2500 MHz is charged with footnote S5.402 to protect Radio astronomy in the band 4990-5000 MHz from second harmonic emission.
  3. The Methanol line at 6668 MHz, which was formerly unknown to the Radio Regulations, now receives protection by two footnotes: the band 6650 - 6675.2 is included in footnote S5.149, which lists all shared Radio astronomy bands, and the new MSS feeder link (space-to-Earth) allocation at 6700 - 7075 MHz is charged with footnote S5.458C to protect observations of the methanol line from unwanted emissions. The new article 29 (formerly article 36), which defines the "service" of Radio astronomy, now contains a reference to ITU-R RA769 to point out the extreme sensitivity and vulnerability of Radio astronomy.
  4. The new recommendation COM5-A calls for sharing studies between Radio astronomy and MSS in the bands 1610.6 - 1613.8 MHz and 1660 - 1660.5 MHz. The emphasis is on technical means to be adopted by MSS systems when operating within a coordination zone around a Radio astronomy observatory.
K. Ruf - Bonn

8. CEPT SE28

CRAF participates in the CEPT SE28 project team. This CEPT Spectrum Engineering project team deals with the compatibility between MSS and other services in the 1.6 GHz range. This project team is basically the successor of project team SE17, which gave in its report a.o. estimated/recommended coordination distances for radio observatories ranging roughly between 170 and 280 km, depending on assumptions of propagation model, elevation angle, traffic density, etc. The CEPT had accepted this report and forwarded to the ITU for further consideration. However, MSS operators felt that the results were too pessimistic. This feeling was taken over by some administrations and the CEPT had to re-do its homework. For this SE28 is working.

During the SE17 meetings there were usually about a dozen people including from Iridium and from INMARSAT. About 25 participants participate in SE28. They are from administrations, MSS organizations and CRAF.

The meetings dealt so far with a discussion of the assumptions for radio astronomy, like e.a. antenna sidelobe levels, antenna gains, elevation angles used, S/N degradation factors due to RFI, etc.

CRAF explained that the levels of harmful interference to the Radio Astronomy Service (ITU-R RA 769) are in fact realistic and quite friendly to active services. CRAF also presented a document on various experiences with harmful interference from satellites (e.g. GLONASS, GPS, ASTRA).

Different systems for inhibiting emissions from MSS were discussed like e.g. the solution

Several times the MoU between NRAO and Motorola was mentioned. This MoU turned out to be a very severe problem: in Germany the Fixed Service had to comply to the wishes of Motorola. If RAS had had no MoU it would be much easier to keep other services in its rights. An argument is that when radio astronomy can accept a deal with Motorola, other users should do the same (since the RAS problems are the most difficult).

CRAF has unanimously rejected the MoU with Motorola. CRAF indicated further that a preliminary analysis of the beacon solution carried out at Jodrell Bank indicates two problems: one concerns the effect of the beacon on the radio astronomy receiver, and the other concerns the unwanted emissions from the beacon into the band 1610.6-1613.8 MHz. At Jodrell Bank, a 1 mW beacon would be sufficiently powerful to cause problems in the receiver and would need to be filtered out at RF implying loss of sensitivity. Not all European observatories have been consulted yet. Furthermore, more input is needed from the MSS operators and RAS observatories like specific numbers, multiple beacon installations. It was said that the implementation of the beacon solution is very site dependent. But note: the beacon solution helps only for the uplink problem: not for the downlink.

CRAF explained the difficulties of sharing between RAS at 1610.6-1613.8 MHz and MSS downlink at 1613.8-1626.5 MHz. It is noted remarkable that a primary service (RAS) which has operated in the band for nearly 30 years is asked to sacrifice 50% of time to the unwanted emissions of an incoming service (MSS) which is sencondary in an adjacent band. The MSS is asked to sacrifice nothing. CRAF recommended better design of the MSS equipment, better traffic control and coupling of MSS with RAS observatories (not the other way around). CRAF also explained that this is killing for a number of RAS projects, like monitoring projects.

During a regulatory discussion it was made clear that the ITU-R Radio Regulations imply that a newcomer in a frequeny band has to adjust his system in order not to interfere with those applications already using this band. In an allocated band it is: first come - first serve.