CRAF Newsletter 2003/2
November 2003
The European Science Foundation is an association of its 70 member
research councils and academies in 27 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.
Contents
This summer, 7 European radio astronomers attended the four week 2003 World
Radiocommunication Conference, WRC-03, in Geneva. All things considered, CRAF is satisfied
with most of the decisions taken at the Conference regarding European radio astronomy. The
agenda for the next Conference, WRC-07, has a number of agenda items of great interest to
CRAF, e.g., on the protection of the 1.4-GHz neutral hydrogen line band and on the continuation
of band-by-band studies of unwanted emissions into radio astronomy bands. Unfortunately, the
European proposal on the protection of future giant radio astronomy instruments (such as ALMA and SKA)
was not selected for the agenda of WRC-07; CRAF will endeavour to have this issue studied
within the appropriate Working Parties of the ITU.
Finally, this will be my last Chair’s corner – henceforth, it will be to Roberto Ambrosini
to convey his comments. I wish him all the best in trying to keep our windows on the
Universe clean.
Wim van Driel - Paris Observatory
Dr. R. Ambrosini will succeed Dr. W. van Driel
as chairman of CRAF from 1st January 2004.
Dr. Roberto Ambrosini was born in 1949 and graduated cum Laude in 1974 from the University of Bologna
in Physics with a PhD Thesis on Gamma Ray astronomy. Since 1975 he has worked at the
Institute of Radioastronomy (IRA) of the National Council of Research (CNR) in Bologna, Italy, where
he holds the position of senior scientist (primo ricercatore).
His main field of interest is the development of new instrumentation for radio astronomy.
He started as a co-designer of the MarkIII upgrade of the Northern Cross at the Medicina station,
followed by the first Italian 32-meter telescope for VLBI, at Medicina, and later the second one
in Noto. He has been Technical VLBI friend from the project start up to 1991, as well as the
chairman of many Control Commissions for the industrial development of the hardware. He has been a
promoter of the technical specifications of the 64-meter SRT (Sardinia Radio Telescope) at present
under construction, and he has actively organized four radio frequency interference (RFI) measurement campaigns for the site selection and
he is now member of the Project Office for this new instrument.
He has a wide range of experience in the design and construction of cryogenic receivers up to
millimeter wavelengths; in the synthesis of timing and local oscillator signals with extremely
high phase stability, while locked to atomic time and frequency standards, as required for the
VLBI and Doppler tracking of interplanetary spacecraft. By this last technique he opened at IRA
a new research field in Radio Science (RS), getting the support of the Italian Space Agency, in
order to track the Ulysses spacecraft and, more recently, the Cassini mission,
up to Ka-band. Within this context he is now an official member of the joint NASA-ASI Radio Science
Team of the Cassini mission.
He presented all above activities at many international conferences and as author
of numerous publications in refereed journals and conference proceedings.
Since the beginning of his studies on the anomalous propagation of radio waves at UHF and SHF,
he has been involved in the issues of radio-astronomical frequency protection from man- made
interference. In July 2001 he was selected as the Italian member of CRAF. Since 2002 he has been
a member of the RFI Working Group for the site selection of the
SKA.
The 37th CRAF meeting was held on 16-17 October in the Collegium Majus of the Jagiellonian University
at Kraków at the invitation of the Astronomical Observatory of this university.
Considering the appointment of the CRAF chairman, Dr.W.van Driel, as Chairman of the IUCAF
in June 2003, CRAF proposed to the ESF to nominate Dr. R. Ambrosini (Bologna) as his successor
from January 1, 2004.
Key items discussed were:
- evaluation of the results of the ITU-R World Radiocommunication Conference 2003, WRC-03.
Two important actions taken by WRC-03 related to the registration of radio astronomy stations: (1) notification of the type
of radio astronomy station (VLBI, single dish and/or connected interferometer array); (2) notification
of the minimum elevation angle at which a radio telescope conducts observations;
- consideration of the draft agenda for WRC-07/10: most relevant for radio astronomy are
an agenda item to continue studies related to FSS feeder links near 1.4 GHz and the completion
of the work left over from ITU-R TG1/7 on Band-by-Band studies, which will be continued in ITU-R TG1/9;
- Broadcasting-satellite developments in the band 620-790 MHz: preliminary studies
show that although the loss of data to radio astronomy from transmissions from a satellite in a
highly elliptical orbit (HEO) in the Broadcasting Satellite Service (BSS) remains within the maximum
tolerable level of 2% over the observable sky, the resulting data loss is mainly concentrated towards
high elevation angles (above about 75º, depending on geographical latitude), which may impose serious
practical constraints for radio astronomical observations, particularly using transit instruments;
- Revision of the Stockholm 1961 Agreement on Broadcasting at the Regional Radiocommunication
Conference 04/05: the protection of radio astronomy in the band 608-614 MHz needs to be properly retained;
- Extension of the frequencies used by the Iridium satellite system: CRAF has brought this
issue to the attention of the CEPT, considering the ESF/CRAF-Iridium Agreements concluded in 1998;
- CRAF noted with great concern the continuing interference from the space-to-Earth transmissions of
the GPS L3 signal at 1381 MHz. It has started discussions with the GPS administration to solve this matter;
- The development of Ultra-Wide Band, UWB, below 10.6 GHz and short range radar, SRR, at ~24 GHz
remains a source of great concern to CRAF. In particular, the pressure on the protection of radio astronomy
in frequency bands to which footnote 5.340 applies (“all emissions are prohibited”) enhances these concerns;
- The developments on Power Line Transmissions (PLT) may have crucial consequences for, e.g.,
the perspectives for LOFAR: according to the PLT radiation limits that are currently considered, LOFAR
may well become “PLT-limited”.
- CRAF appreciated the decision by the Russian administrations to discontinue the Global Transmission
System experiment on board the International Space Station at 1428 MHz.
The 2003 World Radiocommunication Conference, WRC-03, was held between 9 June and 4 July 2003 in Geneva, Switzerland.
Over 2200 Delegates, the largest number ever, from 138 ITU Member States attended the Conference. The delegates
considered some 2500 proposals, and over 900 numbered documents relating to 50 Agenda items. The output of the
Conference consists of 527 pages of new and revised text of the Radio Regulations. Seventeen radio astronomers from
a total of 12 countries, including 7 European countries, attended the Conference.
Out of a total of 50 agenda items, about a dozen were of interest to radio astronomers. Most of these involved
allocations to satellite downlinks, adjacent or close to radio astronomy allocations. For such scenarios, WRC-03
adopted regulatory measures to protect radio astronomy and called for further studies to be completed
before the next WRC, i.e. WRC-07. Some of these are listed in section 5 of this Newsletter.
Agenda items that were of particularly great interest for CRAF were item 1.8.2
on "unwanted emissions" and item 1.16 on "MSS feeder links around 1.4 GHz".
On these agenda items the following conclusions were reached:
a.i. 1.8.2:
This agenda item was one of the most difficult of the Conference. The final compromise
was based on CEPT, APT, Arab Group and Canada inputs.
For the radio astronomy bands, the main thrust is a new Resolution for Consultation
(Resolution 739) for six band-pairs with clear guidelines on how to deal with
the radio astronomy band protection issue during the design and construction (pre-launch)
phase of the satellite and after its launch. This contains design criteria based on radio
astronomy protection levels without having the burden of pre-launch verification of these
limits. A footnote in Article 5 of the Radio Regulations attached to the relevant bands refers
to this Resolution. A second new Resolution (740) calls for further studies on bands that
showed potential problems during the discussions and some band-pairs that have not yet been studied.
Also for the RAS case there is an Agenda Item on WRC-07 relating to the review of the Resolution
for Consultation, but this may not necessarily result in the inclusion of hard limits for
the radio astronomy protection in the Radio Regulations.
ITU-R Study Group 1 has recently created a special Task Group 1/9 to complete the necessary
studies before WRC-07.
on a.i. 1.16:
WRC-03 made new secondary allocations to the FSS in the bands 1 390 - 1 392 MHz and 1 430 -
1 432 MHz for feeder links in the (Earth-to space) and (space-to-Earth) directions, respectively,
for non-GSO MSS satellite networks with service links operating below 1 GHz. Initially
the discussions were rather polarized between a few countries supporting the US proposal
for a primary allocation, and most countries, who, as Europe, opposed any new allocation.
The final compromise was reached near the end of the conference, with secondary allocations,
but without the possibility of using them until WRC-07 has reviewed the compatibility studies
in response to the new Resolution 745 and taken appropriate action.
CRAF considers that the results of WRC-03 are reasonably acceptable for radio astronomy in Europe.
The preliminary agenda of WRC-07 contains five items of direct interest to
radio astronomers:
1.8: to consider the results of ITU-R studies on technical sharing and regulatory provisions for the
application of High Altitude Platform Stations operating in the bands 27.5-28.35, 31-31.3, 47.2-47.5 and
47.9-48.2 GHz;
1.9: to review the technical, operational and regulatory provisions applicable to the use of the band
2 500-2 690 MHz by space services in order to facilitate sharing with current and future terrestrial
services without placing undue constraint on the services to which the band is allocated;
1.11: to review sharing criteria and regulatory provisions for protection of terrestrial services,
in particular terrestrial television broadcasting services, in the band 620-790 MHz from BSS networks
and systems;
1.17: to consider the results of ITU-R studies on compatibility between the fixed-satellite service
and other services around 1.4 GHz;
1.21: to consider the results of studies, and proposal of regulatory measures regarding the protection
of the radio astronomy service from unwanted emissions of space services regarding the compatibility
between the radio astronomy service and the active space services, in order to review and update, if appropriate, the
tables of threshold levels used for consultation that appear in the Annex to Resolution 739 (WRC-03);
The ITU Council will adopt the final version of the WRC agenda.
The preliminary agenda for WRC-10, under Agenda item 2.2 calls for consideration
of frequency allocations between 275 GHz and 3 000 GHz, taking into account the result of ITU-R studies. It
also allows administrations to submit details of systems which operate between 275 and 3 000 GHz,
for inclusion in the Master International Frequency Register (MIFR) and instructs the ITU-R Radiocommunication
Bureau to accept such filings, for information purposes. Agenda item 2.7 calls for consideration
of the progress of ITU-R studies concerning the technical and regulatory issues relative to the fixed service
in the 81-86 and 92-100 GHz frequency bands, taking into account Resolution 731 (WRC-2000), on sharing
between active and passive services above 71 GHz.
A number of other items on the preliminary agendas for WRC-07 and WRC-10 may also have a large impact on radio astronomy,
and several agenda items need to be followed carefully by the radio astronomy community.
Discussions on the deployment in Europe of Short Range Radar for automotive applications, SRR,
at ~24 GHz are ongoing. The European Commission's DG Information Society strongly supports this development in its
e-Safety programme.
SRR at ~24 GHz is one of the key issues
of the e-Safety working group and is seen as a major instrument to improve road safety. However
no allocation exists at ~24 GHz for the SRR application (with a bandwidth of 5 GHz) in the ITU Radio Regulations
or in the European Common Allocation Table. It should also be noted that SRR cannot be regarded as a safety service
application according to the definitions of the ITU Radio Regulations since it will operate on a basis of not causing interference
and accepting interference from other radio applications. The automotive industry even expressed the opinion
that disabling SRR after the occurence of interference does not cause any disadvantages to the driver compared
with conventional vehicle operation (sic!).
CEPT project team SE24 studied the compatibility between SRR at ~24 GHz and radiocommunication services and concluded
that SRR at ~24 GHz is incompatible with the Earth Exploration-Satellite Service, the Fixed Service,
and the Radio Astronomy Service. SE24 is in favour of moving SRR from frequencies around 24 GHz to frequencies
around 79 GHz, where an allocation to the Radiolocation Service already exists. SE24 studies have shown that
for the broadband component of SRR at ~79 GHz regulatory scenarios could be found to enable co-existence between SRR and radio astronomy.
It is also noted that the band 23.6-24.0 GHz is allocated exclusively to passive services, and footnote 5.340 applies which states that "all emissions are
forbidden" in this band. SRR will violate these regulations if
it produces emissions (even after heavy filtering) in this band, as is foreseen by the design of SRR at ~24 GHz.
CRAF notes that the CEPT studies did not address the compatibility of SRR emissions produced in the band
23.6-24.0 GHz with radio astronomy since the protection criteria for radio astronomy in this band apply to unwanted emissions
only - as is explicitly stated in ECC Report 23 on this matter.
Recently, suggestions were made that "specific measures be taken to avoid interference from SRR equipment
to Radio Astronomy stations using the 23.6-24 GHz band. One measure could be manual or automatic switch off
of the SRR system within the protection range of the RAS stations” and that "negotiations” between car manufacturers
and CRAF should take place to find such measures.
Considering the mentioned footnote 5.340, CRAF opposes any “negotiation” on measures to enable the deployment
of active devices in the band 23.6-24.0 GHz. In addition, CRAF notes
that the conclusions on the incompatibility between SRR at ~24 GHz and radio astronomy noted in
ECC Report 23 imply that any deployment of SRR in the band 23.6-24.0 GHz will harm radio astronomy.
European radio astronomy stations operating in the frequency band 1330 - 1400 MHz are experiencing strong
harmful interference at a frequency of about 1381 MHz. This interference is generated by transmissions
from the GPS L3 channel.
An example of this type of interference observed with the Westerbork Synthesis Radio Telescope,
WSRT, in the Netherlands is shown in Figure 1.
The absolute scale for the amplitude of the interference signal is not calibrated
since the antenna gain into the direction of the satellite, which was emitting in the far sidelobes
of the antennas, is not known.
The indicated level of detrimental interference for the
observations presented in the figures below is -239 dB(W/m2/Hz), determined using using the
methodology of Recommendation ITU-R RA.769, which includes the assumption that the
interference is received through the far antenna sidelobes, where an antenna gain of 0 dBi applies.
Fig.1: Intensity of the interference signal from GPS L3 observed through the far sidelobes
at the WSRT on August 25, 2002, at 20h20m25sUT. The data concern an
observation of a radio source at 23h36m35.20s right ascension
and 26o40’36.00” declination (epoch J2000). The figure shows a detailed spectrum in two
linear polarization channels (noted as XX and YY) for an integration time of 0.8 minutes. The amplitude
scale is in units of Jansky (1 Jansky = 1 Jy = 10-26 Wm-2Hz-1). The intensity
of the astronomical source is ~100 mJy. Note that the signal has sidebands that continue to ring throughout the
entire 20 MHz band that is displayed, but at a lower level that is not visible on the present scale.
Close examination of the spectrum of the GPS L3 transmissions shows a double peaked spectrum
with the following four properties, which are all in agreement with those of the interfering signal:
1) a peak separation of ~300 kHz;
2) a central dip of ~2dB;
3) a 3 dB bandwidth of ~800 kHz;
4) a ripple in the interferometer phase frequency of 1 MHz (not shown here).
On the basis of these parameters and the fact that the centre frequency of the interfering signal
is 1381.05 MHz, CRAF considers that the interference presented in Figure 1 can positively be identified as L3.
It should be noted that in the ITU Radio Regulations for Region 1 the
band 1300 - 1350 MHz includes a primary allocation to RADIONAVIGATION-SATELLITE (Earth-to-space)
and no allocation to a space service in the band 1350-1400 MHz. Thus no space-to-Earth transmissions
are allowed in Region 1 according to these Regulations. For the frequency band 1330-1400 MHz footnote
5.149 applies, which states that “administrations are urged
to take all practicable steps to protect the radio astronomy service from harmful interference.
Emissions from spaceborne or airborne stations can be particularly serious sources of interference
to the radio astronomy service (...)”.
CRAF considers that a regulatory solution for this issue is required, in order to avoid the
creation of an undesirable regulatory precedent, where the operation of an application is
allowed in conflict with the ITU Radio Regulations.
On this matter CRAF is currently in the process of discussion with concerned Administrations.
The discussions with ESA, some administrations and the Russian Space Agency and
“ENERGIA” concerning the 1428-MHz space-to-Earth transmissions of the Global Transmission System experiment on board the
International Space Station (see CRAF Newsletters 2002-1 and
2002-2) have resulted in an agreement that was reached in May 2003
between Rosaviakosmos, RSC Energia and the Russian Academy of Sciences. This agreement includes
the information that “GTS experiments were cancelled in July 2002 and GTS has not been activated
since August 2002”. It also decides to “Disconnect the 1428 MHz equipment from the power source and
disconnect it from the transmitting antenna”.
ALMA = Atacama Large Millimetre Array
APT = Asia Pacific Telecommunity
ASI = Angenzia Spaziale Italiana
BSS = Broadcasting-Satellite Service
CEPT = Conference of European Post and Telecommunication administrations
CRAF = Committee on Radio Astronomy Frequencies (ESF)
DG = Directorate General (European Commission)
ECC = Electronics Communications Committee (CEPT)
ESA = European Space Agency
ESF = European Science Foundation
FSS = Fixed-Satellite Service
GPS = Global Positioning System
GSO = Geo-Stationary Orbit
GTS = Global Transmission System Experiment
ITU = International Telecommunication Union
ITU-R = International Telecommunication Union - Radiocommunication Sector
LOFAR = Low Frequency Array
MSS = Mobile Satellite Service
NASA = National Aeronautics and Space Administration (USA)
PLT = Power Line Transmission
RAS = Radio Astronomy Service
RFI = Radio Frequency Interference
RRC = Regional Radiocommunication Conference (ITU-R)
SE = Spectrum Engineering (Working Group of ECC)
SHF = Super High Frequency
SKA = Square Kilometre Array
SRR = Short Range Radar
TG = Task Group (ITU-R)
UHF = Ultra High Frequency
UWB = Ultra Wide Band
VLBI = Very-Long-Baseline Interferometry
WRC = World Radiocommunication Conference (ITU-R)
WRC-03 = WRC 2003
WRC-07 = WRC 2007
WRC-10 = WRC 2010
WSRT = Westerbork Synthesis Radio Telescope
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Editorial Group: R. Ambrosini, R.J. Cohen, P. Scott, W. van Driel
Last modified: 22 December, 2003