Preparing for the New Area of Radio Astronomy
By: Tam Huynh &
Dominion Radio Astrophysical Observatory (DRAO) in Penticton recently
hosted RFI2004, an international workshop dedicated to Radio Frequency
Interference and Interference Mitigation.
The workshop was held July 16-18, 2004.
Astronomers and engineers from around the world were invited to the
Okanagan to find ways to minimize the impact of the growing levels of
man-made radio interference in space.
For radio astronomers, the Radio Frequency
Interference (RFI) environment continues to worsen, making this a critical
issue in the development of the next generation of radio telescopes. Radio Astronomy requires a greater spectrum
for its services, development of new radio telescopes and greater
Canada was invited to RFI2004 to discuss the Spectrum Management
Operation. We brought the Spectrum Explorer, which was mounted on a
mobile trailer, to demonstrate some of the operations of Spectrum
Management measurement and analysis. Gord Herrmann,
Greg Corbett and
Micheal Amyotte from the Okanagan Kootenay District Office were on site to
demonstrate the trailer to delegates.
IC's demonstration was extremely successful, with approximately 25 of the
75 delegates touring the trailer.
The workshop was attended by
Tam Huynh and
Chantal Gazaille from DG Spectrum Engineering. The seminars
proved to be very interesting, covering a range of issues from the
scientific, technical and regulatory issues associated with Interference
Mitigation, to field experiences and demonstrations of new techniques.
RFI2004 was a precursor to the Square
Kilometre Array Conference (SKA04), an international meeting to discuss
and refine the science goals and telescope concepts for the Square
Kilometre Array (SKA), the world's largest radio telescope, currently
being planned for construction in the next decade.
of you may be still be asking yourselves why these issues are so
Basically, to study distant sources,
scientists from around the world need to be able to decipher radio
emissions from the universe. These are currently being masked by local
signals. To fulfill its objectives of discovering the universe, the New
Radio Astronomy requires a greater allocation of spectrum for its
services, more advanced radio telescopes, and more protection.
The Dominion Radio
The full array of DRAO's
In current practice, radio-astronomic observations are done within
frequency bands allocated for this service. Due to the general expansion
of the universe and the doppler effect, the observed frequencies of the
spectral features of very distant sources are ‘red-shifted’  to lower
frequencies that can be up to 5 times smaller than their original
New Radio Astronomy, advanced radio telescopes will be required to ‘see’
across a wider range of spectrum, including frequencies well outside the
bands presently allocated to the radio astronomy service. For
example the 21 cm spectral line (1400-1427 MHz, excited by interstellar
neutral hydrogen HI), which has a rest frequency of 1400.4057 Mhz, can
shift to a lower frequency and be observed at 430 Mhz for a distant
The intensity of radio astronomy signals is well below that of man-made
signals, yet the observations in the New Radio Astronomy need to mitigate
the effects of human-generated interference. In other words, it's a
crowded and noisy universe.
New methods and techniques for RFI
mitigation have been developed and were presented at RFI2004 by the
research community in radio astronomy. One way to do this is by
establishing radio-quiet zones that call for protection from many levels:
global regulatory protection (ITU Radio Regulations), local protection
(Regulations at national level), and self-protection (computers,
electronics associated with telescope control, signal processing).
There are already some existing Radio quiet
zones in the world , for example Greenbank, West Virginia set one up in
1956; the 300m Arecibo Radio Telescope in Puerto Rico; the Giant Meter
Wave Radio Telescope GMRT in Pune, India; the Atacama Large Millimeter
Array ALMA, in the Atacama Desert, Chile.
The Square Kilometre Array is a global project to design and build a next
generation of radio telescope that will have advanced features. These
will include a sensibility 100 times higher than current radio telescopes,
a huge collecting area of one square kilometre.
Eleven countries are participating to this
project: Australia, Canada, China, Germany, India, Italy, Poland, Sweden,
the Netherlands, UK, and USA. Candidates competing for the SKA sites are:
Australia, South Africa, and China.
In the design of SKA concept and
technology, seven proposals from Australia, Canada, China, Europe, India
and the US are competing to gain acceptance. A detailed description of the
Canadian proposal, the “Large Adaptive Array", can be viewed at NRC's
web site. A description of the SKA project and these proposals are
found at www.skatelescope.org. In the SKA timeline, the site and concept
selection will be done by 2005 and 2007 respectively; operation of the SKA
starts by 2020.
Besides Radio Frequency Interference (RFI) mitigation techniques, the New
Radio Astronomy has to gain the support of regulatory bodies at various
levels, from global regulations (through ITU-R, WRC) , regional (CITEL,
CEPT, APT) to national (Industry Canada) . Other sources of RFI that
are growing in importance and may become disturbing in the near future
are: ultra wideband applications, power line communication system, licence
exempt devices operating in the 5Ghz band with transmit power up to 1W.
While the Radio Astronomy service is preparing to enter a new area, Canada
is present and well represented in the community. Dr. Ken Tapping from
the National Research Council, Herzberg Institute of Astrophysics at the
Dominion Radio Astrophysical Observatory (DRAO) in Penticton sits in the
TG 1-8 of ITU-R and is an IUCAF member. As well, the DRAO was the host of
RFI2004 and SKA2004.
Although not a candidate for the SKA site,
Canada is one of the seven proposals in the design and development of the
SKA technology, with the Large Adaptive Reflector (LAR) concept being
developed at DRAO. This is the process where several reflective panels
positioned to form a parabolic dish are used to converge radio signals
from space to a feeder suspended at the focus point of the parabolic dish
by a tethered balloon at least 500m overhead.
On the protection issue, DAO is also
concerned about the recognition and establishment of the observatory as a
radio-quiet zone. There is a housing development and a golf club on the
road to the DRAO (about 2km away). Another concern is the Coordination
with the US for interference from south of the border (i.e., interference
from Aeronautical Mobile services in Monumental, WA ).
These concerns are all valid and will
hopefully be managed successfully in the future. Eliminating interference
will ensure a bright future for Radio Interference, and the DRAO and IC's
SITT will definitely be playing a role.
 Spectrum Management for Radio Astronomy, Proceedings of the IUCAF
Summer School, 2002
 Jim Cohen, Radio-Quiet Zones: National and International Perspectives,
 Sharing analysis between Aeronautical Mobile services in Monumental
Mountain, WA, US and Dominion Radio Astronomy Observatory in Pentiction,
BC, Canada. Industry Canada, Doc. TN-277