CRAF Newsletter 2003/1
May 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
The World Radiocommunication Conference 2003 (WRC-03) organized by the International Telecommunication Union (ITU)
from 9 June till 4 July in Geneva is a very important event for radio astronomy. This special edition of the CRAF
Newsletter is devoted to radio astronomy issues at WRC-03.
CRAF has participated actively within CEPT in the preparation of European Common Proposals, ECPs, for the numerous
WRC-03 agenda items of concern to radio astronomy and supports them. The specific interest in these agenda items
of radio astronomers in various CEPT countries is listed in section 4 of this Newsletter.
The basic issues at hand of particular interest to the Radio Astronomy Service are similar to those addressed
at previous WRCs, e.g. proposals for the allocation of new satellite downlinks adjacent to radio astronomy
bands, and placing limits on the levels of unwanted emissions from satellites into bands used for radio astronomy.
To protect the fundamental science done by radio astronomers great care has to be taken at the WRC concerning the
regulation of these issues.
The worldwide radio astronomy community is working towards the construction of a new generation of giant radio
telescopes, with collective surfaces of up to a square kilometre and operating in the frequency domain of 150
MHz to 950 GHz. CRAF supports the ECP on the necessity for studies on the required operational conditions for
their successful operation.
Wim van Driel - Paris Observatory
The science of radio astronomy plays a key role in increasing our understanding
of the universe in which we live. Radio astronomy is a so-called passive service,
in the sense that it never causes interference to other users of radio.
Unfortunately it is becoming increasingly difficult to protect radio
astronomy observatories from man-made interference,
as use of the radio spectrum increases on Earth and in space.
On behalf of European radio astronomers, CRAF, the Committee on Radio Astronomy
Frequencies of the European Science Foundation does
its best to keep the frequency bands used by radio astronomers free from interference.
A brief introduction to the ESF is given at the top of this Newsletter.
CRAF works towards this aim by:
- coordinating the case for radio astronomy in discussions
with European administrations, the Conférence Européenne des
Postes et des Télecommunications, CEPT, the European Commission and private
telecommunications
operators;
- acting as the European voice in concert with other groups of radio
astronomers in discussions within the international bodies that allocate
frequencies;
- initiating and encouraging scientific studies aimed at reducing
interference at source and the effects of interference.
The Committee acts also to help EISCAT - the European Incoherent Scatter
Scientific Association - whose important
experiments in the polar ionosphere face similar severe interference
problems.
The members of CRAF are appointed by the ESF Executive Council for a three
year period, after consultation through the appropriate channels. They are
drawn among experts active in the field of frequency management at
radio-astronomical observatories in Europe.
Radio astronomy is a dynamic science in Europe.
The following table lists the
European countries in which radio astronomy stations are operating and the number of stations involved.
All these countries also participate actively in the work of CRAF.
| country | number of RAS stations | key
frequency interests | WRC-03 agenda items of interest |
| | |
| Austria | 1 | decameter research | 1.8.2, 1.20 |
| Belgium | 1 | <1 GHz | 1.8.2, 1.20 |
| Czechia | 1 | 0.8 - 5 GHz | 1.8.2, 1.15, 1.16, 1.31, 1.33, 1.34 |
| Finland | 1 | >~20 - ~120 GHz | 1.8.2, 1.13, 1.25, 1.32 |
| France | 3 | all | 1.8.2, 1.13, 1.15, 1.16, 1.20, 1.25, 1.31, 1.32, 1.33, 1.34 |
| Germany | 3 | >0.4 - ~100 GHz | 1.8.2, 1.11, 1.15, 1.16, 1.20, 1.25, 1.31, 1.32, 1.33, 1.34 |
| Greece | 1 | <1 GHz | 1.8.2, 1.20 |
| Hungary | 1 | 1 - 1.5 GHz | 1.8.2, 1.15 |
| Italy | 4 | 0.3 - 44 GHz | 1.8.2, 1.13, 1.15, 1.16, 1.20, 1.25, 1.31, 1.32, 1.33 |
| Latvia | 1 | 0.3 GHz and ~10 GHz | 1.8.2 |
| Netherlands | 2 | 0.2 - 8 GHz | 1.8.2, 1.15, 1.16, 1.20, 1.31, 1.33 |
| Poland | 2 | 0.1 - 7 GHz | 1.8.2, 1.15, 1.16, 1.20, 1.31, 1.33 |
| Portugal | 1 | 0.1 - 0.7 GHz | 1.8.2, 1.20 |
| Russia | 14 | 1.6 - 23 GHz | 1.8.2, 1.11, 1.15, 1.16, 1.31, 1.33, 1.34 |
| Spain | 3 | 1.6 - 275 GHz | 1.8.2, 1.13, 1.15, 1.16, 1.25, 1.31, 1.32, 1.33 |
| Sweden | 1 | 1.3 - 116 GHz | 1.8.2, 1.13, 1.15, 1.16, 1.25, 1.31, 1.32, 1.33 |
| Switzerland | 1 | 0.1 - 4 GHz | 1.8.2, 1.20, 1.33 |
| Turkey | 1 | 86 - 116 GHz | 1.8.2 |
| Ukraine | 7 | | 1.8.2, 1.20 |
| United Kingdom | 6 | 0.04 - 44 GHz | 1.8.2, 1.11, 1.13, 1.15, 1.16, 1.20, 1.25, 1.31, 1.32, 1.33, 1.34 |
Europe also participates in radio astronomy stations in ITU Region 2, on Hawaii, in Chile and in the
USA operating at mm-wave and sub-mm-wave frequencies.
The European Incoherent Scatter Scientific Association (EISCAT) operates 4 stations in northern
Scandinavia at frequencies 0.2 - 0.9 GHz.
Radio Astronomy is continuously working on the improvement of its instruments, in terms of increased
sensitivity, spectral-, time- and angular resolution. A variety of technologies are applied for this, such as
single dish telescopes with dimensions of up to 300 meters, radio interferometers with baselines
extending beyond the dimensions of the earth (space Very Long Baseline Interferometry), receiver
backends with up to a million channels, superconducting components and system temperatures only a few
degrees above the absolute zero level.
Considerable technical innovation in the design of radio astronomy antennas will enable the building,
in the timeframe of 2003-2015, of a new generation of instruments with very large collecting areas,
having a sensitivity about a hundred times better than the largest instruments presently in operation.
An additional objective for these new instruments is observation capabilities in various frequency
bands not allocated to the Radio Astronomy Service. These (international) instruments will be built
in very remote areas, where the radio environment may offer better opportunities for protection of
the observations and enhanced protection of the radio environment is sought at their locations only.
It should be noted that most of the large radio telescopes presently in operation will continue to be
used for scientific research once these new instruments become operational.
Since investments for these instruments will be in the order of more than 2 Billion Euros or
US Dollars only a few of them will be built. Three specific telescopes are presently under development,
each of which constitutes a large step forward in observational abilities.
The Atacama Large Millimetre Array (ALMA), will operate in all
atmospheric windows in the frequency range 31 to 950 GHz. This observatory, comprising 64 telescopes
each with a 12 metre aperture will be located on a virtually rainless plateau at an altitude of 5000
meters in the Plain of Chajnantor in the Atacama desert in Northern Chile, in close proximity to the
borders with Argentina and Bolivia.
The total collecting area of this telescope will be a factor of 40 larger than the currently available
largest telescope at the upper end of the covered frequency range and at least a factor 8 at the lower
frequencies. This telescope will be built using the extensive experience of radio astronomers with
observational systems operating at frequencies up to 1200 GHz.
The second instrument, the Low Frequency Array (LOFAR),
is designed to operate in the 10-240 MHz frequency range, with a total collecting area of one square
kilometre. The telescope will consist of dozens of stations, each with numerous antennas (in total about
25000, each the size of a common TV antenna). There will be one core location of 320 hectares
and about 100 smaller locations ranging from two to four hectares each within an area with about
200 km radius. The stations concentrated in the core location
and all other elements of the instrument will be linked through a high-bandwidth optical cable network.
The location for the LOFAR is currently under investigation and will be decided in 2003.
The third instrument, the Square Kilometre Array (SKA),
will be designed to operate in the whole frequency range of about 150 MHz to 22 GHz, with a total collecting
area of one square kilometer. Design studies currently underway are aimed at specifying the operating
frequencies and determining the technology to be used for the telescope. The telescope may actually
consist of two arrays based on two different technologies and covering two complementary frequency
ranges.
There will be up to one hundred stations of about 100 by 100 m in
size, each comprising many antennas. The SKA will have a compact core with 25 percent of the stations,
simulating sensitive single-dish operations, combined with VLBI techniques applied on the longer
baselines towards the more distant stations as far out as 4000 km.
The location for the SKA is currently under investigation and will be decided in 2006 based on
technological, economic, and environmental factors.
The characteristics of the electromagnetic environment in the operating bands of the three
telescopes are totally different. The spectrum below 22 GHz is already used intensely by a
large number of terrestrial and satellite services, and potentially very harmful Power Line
Transmissions (PLT) are planned in the LOFAR frequency range (see item 7 of this Newsletter).
Whereas the spectrum between 30 and 60 GHz is currently being considered for future
large-scale implementation by these services, the active spectrum allocations above 60 GHz
are used only sporadically at present and the implementation of systems emitting
in many of these bands is still many years off.
Nevertheless, it may be necessary to have available in the Radio Regulations some specific
technical and regulatory provisions to ensure the required radio environment at these
observatories. The challenges that need to be faced to enable their successful
and efficient operation include the development of:
innovative, RFI-resistant systems by radio astronomers;
appropriate regulatory instruments for Administrations, which also avoid degrading impact
on active services.
Within the ITU-R Questions need to be defined and studied by all services concerned
(and not only the science services) to make an inventory of possible technical, operational
and regulatory measures, as well as of mitigation techniques, for the creation of the required
radio environment, in order to allow a future WRC to take the required decisions.
In Europe, the issue of Short Range Radar, SRR, is the subject of intensive discussion at the highest
Administrative level, with industry and with organisations representing the interests of the
potentially affected services, i.e. the Earth Exploration Satellite Service, EESS, the Fixed
Service, FS, the Radio AmateurService, RAm and the Radio Astronomy Service, RAS.
Following developments outside Europe, the automobile industry with support of the European Commission
aimed for SRR using a frequency band of 5 GHz centred on 24.15 GHz, i.e. from 21.65 to 26.65 GHz.
The deployment of SRR at ~24 GHz would generate several regulatory and technical problems that are difficult
to resolve. An important regulatory problem is that footnote 5.340 applies to the
frequency band 23.6-24.0 GHz and prohibits all emissions in this band. Technical studies show
that SRR at 24 GHz is not compatible with any of the services operating in the frequency range considered for SRR.
Radio astronomy operating in frequency bands near 24 GHz can be protected only if the e.i.r.p. per SRR device
is at least 80-100 dB lower than the value of -30 dBm/MHz hitherto considered. The scenario for the FS and the EESS
operating in this frequency range is, however, more favourable, but there are still discrepancies
of a few tens of dB between SRR emission levels and protection criteria for FS and EESS.
The CRAF position is that SRR deployment at ~24 GHz as anticipated by the automobile industry violates footnote
5.340 in the band 23.6 - 24.0 GHz and SRR must therefore avoid this band completely. This
view is shared by others as well.
The World Radiocommunication Conference of 1997 allocated the band 76 - 77.5 GHz to the Radiolocation Service.
This decision was specifically driven by the need for a frequency band for vehicular radar applications.
Currently, the automobile industry is looking for a frequency band in the 77 GHz range for SRR. Studies are
underway to address the compatibility between SRR and the potentially affected services, i.e. RAm and RAS.
Power Line Communications stands for a complex of applications that include
- Power Line Telecommunications (PLT or PLC), a means of transmitting high data rates on the
mains electricity network;
- Digital Subscriber Line (DSL), a means of transmitting high data rates on existing copper wire
telecommunication networks, for example plain ordinary telephone systems;
- cable communications, comprising a family of distribution networks that utilise dedicated coaxial cables,
to provide traditional Cable TV and increasingly new Interactive services, including Internet access;
- Local Area Networks (LANs).
It is currently considered that PLC will be deployed at frequencies below 30 MHz. This application is
strongly supported by electricity providers. The impact of the use of power lines for communication
on other users of radio frequencies is considered an issue of electromagnetic compatibility, EMC,
rather than radiocommunications, and it will be resolved by the appropriate organisations. The CEPT
has also addressed this matter and reported pfd levels that will not be sufficient to protect
the most sensitive potential victim services, such as radio astronomy.
Europe is extensively involved in leading edge research in radio astronomy frequencies below 2 GHz.
This frequency range is also of great interest for future radio astronomy because of the development of
a new generation of giant radio telescopes such as the Low Frequency Array Network,
LOFAR, which will have a diameter of 350 km (see section 5) and
for which there is a serious chance it will be located in The Netherlands, with several outlying
antenna stations in Germany.
The European standardization institutes working on EMC issues have not yet finalized their work. But
considering their progress so far, CRAF has serious concerns
that LOFAR will become PLC limited since the presently considered pfd limits exceed the
protection criteria for radio astronomy by more than an order of magnitude.
CRAF's view is that non-radio telecommunications should preferably use fibre optics cables, in order
to prevent radio interference to radiocommunication services.
The World Radiocommunication Conference 2003, WRC-03, will be held in Geneva from June 9 - July 4,
2003. The agenda of this conference contains several items which have relevance for radio astronomy.
CRAF has participated actively within CEPT in the preparation of European Common Proposals, ECPs,
for WRC-03 on these agenda items and supports them.
CRAF offers some additional comments on a number of agenda items:
1.8.2: The regulation of unwanted emissions to protect the passive services has been on the
ITU-R agenda for almost a decade. The CEPT proposes a regulatory solution for implementing pfd
limits for GSO systems and epfd limits for non-GSO systems based on the epfd concept as defined
in RR Article 22 in the relevant bands.
The results obtained from the band-by-band studies shall be the basis for bands where limits
will apply. Some radio astronomy (RAS) bands are already protected in the Radio Regulations
from unwanted emissions (see Nos. 5.208A, 5.443B,
5.511A and 5.551G): it is proposed to address
the protection of these RAS bands in the same way. Depending on the outputs of the discussions on
Agenda Item 1.15 dealing with footnote 5.443B and Agenda Item 1.32 dealing
with footnote 5.551G, there would be a need to review these footnotes and
to ensure consistency between all proposals addressing the protection of RAS bands with regard to
unwanted emissions from space services.
1.16: During the WRC-03 preparation no evidence for the need of feeder links around 1.4 GHz was
demonstrated. Furthermore, ITU-R studies have shown that the introduction of feeder links around
1.4 GHz would imply great difficulties for the protection of both the active and passive services
having an allocation in the frequency bands between 1 350 MHz and 1 452 MHz, and that it is very
unlikely that these can be solved. Therefore, CRAF supports fully the position of active NOC on
this agenda item.
1.31: Particularly the consideration in some proposals to allocate the band 1668-1670 MHz
to MSS (Earth-to-space) needs careful consideration. The Conference Preparatory Meeting for
WRC-03, CPM-03, (Geneva, 18-29 November 2002) concluded that separation distance of the order
of 500 km from a radio astronomy station operating in that band are needed to guarantee
protection of that station. This implies that the deployment of MSS stations in that band
within CEPT countries is basically not possible, considering the geographical density of
radio astronomy stations in Europe. In other regions, this CPM-03 conclusion may imply
restrictions on MSS as well.
The 36th CRAF meeting was held on 27-28 March 2003 at the EISCAT Headquarters in Kiruna, Sweden.
Key items discussed were:
- Notification of radio astronomy stations with the ITU-R, or their update, is urgently needed,
since without proper notification with ITU-R radio astronomy stations may not have the right to claim
protection against interference from various sources, specifically space stations. Consultation with
the national Administrations is required, since only they are mandated to file these notifications with
the ITU-R.
- Broadcasting-Satellite in the band 620-790 MHz: France (Astrium) proposed a project for
satellite broadcasting (BSS) in the band 620 to 790 MHz which led to concern in other CEPT
Administrations. CRAF and France are studying the compatibility between BSS and radio astronomy in the
bands 608-614 MHz and 1330-1427 MHz in the CEPT project team SE27.
- Revision of broadcasting channel plan in ITU-R Region 1 (Stockholm 1961): The ITU-R will convene
a Regional Radiocommunication Conference in 2004/05 (RRC-04/05) on the planning of terrestrial
broadcasting in the VHF/UHF bands, for the combined planning area covering the European Broadcasting Area, the
African Broadcasting Area, and the countries outside the African Broadcasting Area which
are parties to the Regional Broadcasting Agreement Geneva-1989. The interests of radio astronomy
in the band 608-614 MHz were explained to CEPT project team FM24. It was recommended that the
administrations take the radio astronomy interests into account when developing their proposals for the
conference.
- Power Line Transmissions, PLT or PLC: The PLC developments may have crucial consequences for, i.e.,
the perspectives for LOFAR: according to the PLC radiation limits that are currently considered, LOFAR
may well become `PLC-limited'. In a Joint Working Group ETSI, CENELEC and CISPR are currently working on
the definition of the radiation- and product norm for PLC. CRAF is concerned that in this Joint
Working Group the concerns of radio astronomy will not be considered properly.
- Global Transmission System experiment on the International Space Station, GTS: the Russian GTS
administration recognized that the frequency choice of 1428 MHz is wrong and stated that this band will
not be used by the system, which is currently on board of the International Space Station.
- The progress of SE24 compatibility studies on the Ultra Wide Band transmissions and Short Range
Radar at 24 GHz and 77 GHz are being monitored with great attention and concern by CRAF. CRAF participates
actively in the studies within CEPT on these issues.
- It is foreseen that a major revision of the CRAF Handbook for Radio Astronomy will be published
early in 2004.
- CRAF participates actively in CEPT discussions on common European positions on WRC-03 agenda
items relevant for radio astronomy. CRAF supports the European Common Proposals for this conference.
Several CRAF members will participate in the WRC-03 conference.
ALMA = Atacama Large Millimetre Array
BSS = Broadcasting-Satellite Service
CENELEC = European Committee for Electrotechnical Standardisation
CEPT = Conference of European Post and Telecommunication administrations
CISPR = International Special Commitee on Radio Interference
CPM = Conference Preparatory Meeting (ITU)
CPM-03 = CPM for WRC-03
CRAF = Committee on Radio Astronomy Frequencies (ESF)
DSL = Digital Subscriber Line
ECP = European Common Proposal (WRC)
EESS = Earth Exploration-Satellite Service
EISCAT = European Incoherent Scatter Scientific Association
EMC = Electro-Magnetic Compatibility
ESF = European Science Foundation
ETSI = European Telecommunication Standardisation Institute
FS = Fixed Service
GSO = Geostationary Orbit
GTS = Global Transmission System Experiment
ITU = International Telecommunication Union
ITU-R = International Telecommunication Union - Radiocommunication Sector
LAN = Local Area Network
LOFAR = Low Frequency Array
MSS = Mobile-Satellite Service
NGSO = Non-GSO
NOC = No-Change
PLC = Power Line Communication
PLT = Power Line Transmission
RAm = Radio Amateur Service
RAS = Radio Astronomy Service
RFI = Radio Frequency Interference
RR = Radio Regulations (ITU-R)
RRC = Regional Radiocommunication Conference (ITU-R)
SKA = Square Kilometre Array
SRR = Short Range Radar
UHF = Ultra High Frequency (300 to 3000 MHz)
VHF = Very High Frequency (30 to 300 MHz)
VLBI = Very Long Baseline Interferometry
WRC = World Radiocommunication Conference (ITU-R)
WRC-03 = WRC 2003
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Editorial Group: R.J. Cohen, P. Scott, W. van Driel
Last modified: 7 February, 2005