URSI Commission J (Radio Astronomy) Report to CNC

Summer 2004

Dave Routledge, Canadian Commission J Chair, Univ. of Alberta [Dept. Electrical Engineering, Univ. of Alberta, Edmonton, AB T6G 2V4 Canada]

and

Ken Tapping, DRAO, Herzberg Institute of Astrophysics, NRC of Canada

INTRODUCTION

The involvement of Canadian radio astronomers in URSI is important because they are deeply committed to the development of the world's next generation of instrumentation for radio astronomy, and equally important, because radio astronomy's access to the electromagnetic spectrum is under threat. The membership of Canadian Commission J is split roughly equally between persons who observe with radio telescopes or use radio data but do not have direct involvement in improvement of instruments and techniques, and those who do. But roughly half of those in the "technically involved" group do not themselves make astronomical observations or interpret radio data for astrophysical purposes. Canadian radio astrophysical expertise and activity extends into many Canadian universities, large and small, but Canadian technical expertise in radio astronomy resides primarily within the Herzberg Institute of Astrophysics. [...] Historically, many profoundly innovative developments in astronomical instrumentation came from persons who had deep understanding of the technical principles and problems, but who were also involved in active astrophysical research and hence were driven by the needs of the science which the instruments are created to satisfy.

URSI and the conferences it organizes constitute an important channel for technical communication among the radio astronomers of the world, and between them and other users of the electromagnetic spectrum. The mandate of URSI Commission J includes (i) promotion of technical means of radio astronomical observations and data analysis, (ii) support of activities to protect radio astronomy from harmful interference, and (iii) observation and interpretation of celestial radio emissions.

RADIO ASTRONOMICAL FACILITIES

Federal government funding for ALMA and for the EVLA correlator development gives tangible approval of projects which received consensus backing from the entire Canadian astronomical community in the development of the Long Range Plan for Astronomy.

A. ALMA and EVLA

Details are being worked out for the integration of Japan into the Atacama Large Millimeter Array project. The project is currently a two-way partnership between a North American consortium (the U.S. and Canada, under NAPRA) and a European consortium. ALMA will be an aperture synthesis telescope providing high sensitivity, high spectral resolution, and very high angular resolution at mm/submm wavelengths. It will operate initially in four dual-polarization bands between 86 and 720 GHz., on a site at 5000 metres altitude in the Chilean Andes. The agreement with Chile for the land was signed in November 2003, and Chile is now officially part of the project. The current design has sixty-four 12-metre antennas, but addition of Japan as a third major partner will allow the array to be enhanced; e.g. the number of antennas may be increased, since the 12m antennas are the single most expensive item in the budget. Canada is involved in technical developments for ALMA in receiver development for Band 3, the IRMA phase correction system, and in software development and data archiving. In April 2004, the Band 3 Receiver Development project passed its preliminary design review at HIA Victoria.

In New Mexico, radiometric tests of the VertexRSI prototype antenna have produced its first total-power images of Mercury (95 GHz) and Saturn (265 GHz); holographic testing of the AEC prototype antenna is complete and it too is being readied for radiometric tests. Three IRMA devices will be tested on the Smithsonian Millimetre Array in Hawaii in 2004. At HIA, the ALMA Band 3 receiver project remains on schedule, with the noise temperature of the double-sideband SIS mixer design close to achieving the specification of 34 K; the IF amplifiers are also meeting specifications. The HIA test cryostat successfully completed its first cool-down to 3.3 K in February 2004; it will be used to test all future mixers for Band 3 receivers. An ALMA Science Workshop was held in Maryland in May 2004, to highlight the future scientific capabilities of the telescope.

Canada's participation in the Very Large Array Expansion project (EVLA) is part of the North American Partnership for Radio Astronomy Agreement (NAPRA), and it is because of the existence of NAPRA that Canada can be involved in the ALMA project. The objectives of the EVLA project are to increase the capabilies of the VLA by (i) about 104 in continuum sensitivity, (ii) over 10004 in spectral resolution, and (iii) about 104 in angular resolution by adding eight 25m antennas in New Mexico. The wavelength coverage of the VLA will also be extended shortward to 7mm. In addition, a super-compact "E-Configuration" will be established to provide efficient mosaicing capability with angular resolution midway between that of the current compact D-Configuration and the 110m Green Bank Telescope. The heart of the EVLA program is an enormously improved digital correlator being developed by HIA. DRAO's innovative "WIDAR" concept is the key to the design; the conventional design originally planned by NRAO would have been less flexible and less powerful. A key component of the WIDAR correlator is the new EVLA correlator chip; a call for tender was issued by HIA in January 2004. HIA is also designing and testing another key part of the correlator, which is an FIR digital filter. The correlator backend, which converts data coming from the WIDAR correlator into a form useable by scientists, is being designed by NRAO. HIA is participating in the development of the correlator software and its interface to the outside world. NRAO plans to decommission both the existing VLA correlator and the existing VLBA correlator when the WIDAR correlator is fully operational in 2009; the first scientific observations should be possible with the new DRAO correlator in 2007.

B. SKA/LAR

The work underway at DRAO by the team designing the EVLA correlator will in turn provide a springboard for even more advanced systems, including the digital beam-forming and correlation system for the Square Kilometre Array (SKA) project.

Canada has had a leading international role from the outset in the SKA. For high sensitivity, the SKA will require about 1004 the collecting area of the VLA. However, the SKA will also deliver angular resolution of milliarcseconds as an aperture synthesis telescope, with baselines stretching hundreds of kilometres. Each of perhaps thirty antennas must therefore contribute huge collecting area for sensitive cm/dm- wave spectroscopic imaging. Canada's design entry in the competition to establish the technology of the large-area antennas is the Large Adaptive Reflector (LAR) concept, which originated within HIA. This will be an adjustable offset-feed paraboloid constructed nearly flat on the ground for low cost, with light-weight reflecting panels controlled by actuators so that the antenna profile can be continuously adjusted to track objects in the sky. The telescope must have a long focal length (500m) to keep actuator throw minimal and cost low. The feed will therefore be carried under a multiply-tethered aerostat. This LAR concept is being developed by a Canadian NRC/university/industry consortium. For example, a $500,000 NSERC Strategic Research Grant has been obtained by researchers at U. Laval and McGill U. to develop the Confluence Point Mechanism which will fly at the focal point, at the confluence of the tethers, to support and steer the focal plane feed array. Simultaneously, work is proceeding at DRAO on development of focal-plane antenna arrays and receivers.

A 1/3-scale tethered helium aerostat is now flying at DRAO. This is being used to understand the behaviour of the airborne platform, to refine computer models, and to gain experience with ground-handling equipment and techniques. A GPS-based Confluence Point instrumentation package is in use, including a tilt sensor and an ultrasonic wind sensor. Three winches are now installed, but a six-tether closed-loop control system will ultimately be used. A prototype reflector "structure unit" has now been designed and built; this is a triangular steel truss assembly carrying an adjustable surface-support framework, and a corrugated steel surface on which the sheet steel reflector itself rides. The structure unit will be used to test actuation mechanisms, which are required to allow the paraboloidal surface of the LAR to be controlled in real time. Hydraulic actuators of large linear range are now being tested.

As a fully-steerable unblocked-aperture telescope of great sensitivity and moderately high angular resolution, the prototype Canadian Large Adaptive Reflector (CLAR) will be an exciting and versatile astronomical instrument in its own right. It will be extremely useful in Galactic and extragalactic spectroscopic programs, pulsar studies, VLBI observations, etc., in exactly the way that the recently commissioned NRAO 110-metre Green Bank Telescope is useful. It is immensely important that the LAR concept be sufficiently mature technically to survive the future "down-selection" of SKA technology concepts.

Large portions of the Universe in redshift, from before the advent of galaxies to the present, will be accessible to imaging by the SKA because of its broad spectral coverage, its huge collecting area, and its high resolution. The actual construction of the SKA will occur after ALMA. The international SKA consortium currently consists of 14 countries plus 3 more countries which send only official observers to meetings of the International SKA Steering Committee (ISSC). Canada contributes members to the ISSC, the International SKA Science Advisory Committee, and the International SKA Engineering Management Team. A national steering committee for the Canadian SKA project has been formed by CASCA, with representation from industry, universities, and the National Research Council. The 2004 international SKA meeting was hosted in July by Canada.

C. JCMT

The Canadian oversubscription factor on the JCMT is currently 2.6. This testifies to the indispensible role the telescope plays in Canadian radio astronomy with its current suite of instruments. Meanwhile, enormous upgrades are imminent.

The Auto-Correlation Spectrometer Imaging System (ACSIS) has been developed by HIA to produce calibrated spectra from a focal plane array of sixteen 345 GHz receivers. The spectra are produced at the rate of 20 per second, to be gridded and displayed in real time. The correlator hardware was developed at DRAO, and is now complete. The samplers, to convert the sixteen 345 GHz analog signals into digital streams, were also developed at DRAO. For the IF system, down-converter modules were built by Murandi Communications of Calgary; controllers for these modules were developed at DRAO. The ACSIS reduction software runs on an array of dual-processor Linux computers at DRAO and now interfaces successfully with the JCMT control system.

HARP (Heterodyne Array Receiver Programme) is the 16-element focal-plane array of 350 GHz antennas and receiver front-ends for the JCMT Nasmyth focus. In combination with ACSIS it will place 16 beams on the sky, with a multichannel spectrum per beam. It is being built at Cambridge, UK, with contributions from HIA; the HARP-B local oscillator system was completed at HIA Victoria in April 2004, and is being shipped to Cambridge. The ACSIS and HARP projects together will provide the JCMT with fast spectral (heterodyne) imaging capability, and increase the spectral bandwidth and resolution. Image data will be reduced and displayed in real time.

For continuum imaging, SCUBA (Submillimetre Common User Bolometer Array) currently produces 37 beams in a 5 arcmin2 field of view in the 750 and 850 mm atmospheric windows. SCUBA-2 will be a bolometer array far surpassing the current SCUBA in sensitivity and number of beams on the sky: SCUBA-2 will produce ~30,000 pixels in a 64 arcmin2 field of view at 850 and 450 mm. Hence the imaging speed of SCUBA-2 will permit large fields of view to be observed at high sensitivity which are precluded with the current SCUBA camera. SCUBA-2 will be accompanied by a polarimeter and a Fourier transform spectrometer developed at the University of Lethbridge. Funding for SCUBA-2 has been provided by Canada, the UK, and the Netherlands.

Canadians will have access to a high-altitude aperture synthesis array before ALMA is available, through interconnection between the JCMT, the CSO ten-metre telescope, and the Smithsonian Millimeter Array (SMA) at 4000 metres on Mauna Kea. The SMA now has eight antennas in place. The JCMT and CSO telescopes will in turn increase the sensitivity of the SMA. A 20 mm infrared water-vapour bolometer radiometer and a 183 GHz heterodyne water-vapour radiometer (U. Lethbridge) have been tested on Mauna Kea for antenna-based sub-mm phase correction.

D. DRAO

The Synthesis Telescope at DRAO continues to play the lead role in steadily producing high-quality data for the Canadian Galactic Plane Survey (CGPS), as part of the International Galactic Plane Survey (IGPS). The CGPS data set consists of high-dynamic-range mosaiced continuum and polarization 1.4 GHz images, and 256-channel spectroscopic 21cm HI images, all with ~1-arcminute resolution, plus 0.4 GHz continuum images with ~3.5-arcminute resolution. Phase I of the survey comprised 193 fields, and Phase II added 180 more. Phase III observations have now begun. The fidelity of the mosaics is unsurpassed because of the careful inclusion of low-order Fourier components from single-dish telescopes in the 21cm and 74cm continuum mosaics and in the 256-channel 21cm spectral line mosaics.

The 26m DRAO telescope is playing a vital role in providing the carefully calibrated and sidelobe-corrected 21cm spectra for inclusion in the CGPS HI mosaics as low-order Fourier components. For this purpose, the Low Resolution DRAO Survey of HI Emission from the Galactic Plane has been extended to provide the additional sky coverage needed for CGPS Phase II. The 26m telescope is also being used to provide fiducial polarization survey data (M. Wolleben, PhD student) for the 1.4 GHz polarization mosaics, i.e. the fundamental data to which the polarization observations made with the Effelsberg 100m telescope can be anchored. The Effelsberg data in turn will constitute the lower-order Fourier components in the ultimate CGPS polarization mosaics from the Synthesis Telescope.

The IGPS continues the objectives of the CGPS, mapping the atomic, relativistic, and ionized components of the ISM with arcminute resolution, and extends it to imaging most of the plane of the Galaxy. Data are being provided by DRAO (northern declinations), the Australia Telescope (southern declinations), and the Very Large Array (equatorial declinations). CO survey data are being contributed by the FCRAO mm-wave telescope. The IGPS 2004 Science Meeting was held at DRAO in May.

The sensitivity of the Synthesis Telescope continues to be improved by reduction of sources of receiver noise (MSc project, A. Garcia) and antenna noise (MSc project, T. Ng). Ng's MSc project also included computation of instrumental polarization across the Synthesis Telescope's field of view, and these results were presented at the IEEE/URSI conference in Ohio (see below). Other graduate students working at DRAO in 2003 included Ed Reid (PhD, U. of Alberta), Majk Wolleben (PhD, Bonn University), and Owen Davison (MSc, U. of Alberta).

The new observatory building was officially opened in September 2003, and named for Arthur Covington, Canada's pioneer radio astronomer. Covington, a National Research Council scientist, began NRC's program of regular 10.7cm observations of the Sun, and designed and built sophisticated compound interferometers which functioned in the spatial frequency domain as signal-processing telescopes. [...]

The 10.7cm Solar Radio Monitoring program became in 2003 jointly funded by NRC and the Canadian Space Agency. The new arrangement has allowed upgrades to be made in computers, data logging equipment, software, and a new website.

E. Space VLBI

The Canadian S2-Space VLBI correlator at DRAO produced its last output fringes in support of the VLBI Space Observatory Program (VSOP) Space-VLBI mission in August, 2003. These were observations of the Vela pulsar. The S2 VLBI correlator was designed and built at DRAO and was the major correlator for the VSOP Survey program. The correlator produced its first fringes in 1997, and support by the Canadian Space Agency for S2 correlator operation ended on August 30, 2003. CSA support continues for VSOP Survey data reduction and analysis at the University of Calgary Radio Astronomy Laboratory.

The Japanese satellite HALCA carries an 8m telescope and a sophisticated VLBI receiving system in an eccentric orbit to observe high-brightness objects in cooperation with ground telescopes. Almost all the recent VSOP observations have been correlated at the S2 correlation centre at DRAO. The VSOP project pioneered VLBI incorporating space-borne telescopes, but Canada is now planning for future SVLBI missions including VSOP-2 and I-ARISE. In addition, the Russian Space Agency has assigned the Radioastron space VLBI mission (an orbiting 10m antenna and 22 GHz receiving system) the number one priority position in the Russian space astronomy program. Apogee will be near 340,000 km, and the angular resolution will be unprecedented.

F. ODIN

Canada is an international partner with Sweden, France, and Finland in this combined (50/50) astronomy/aeronomy space mission. Scientific support of Odin astronomy in Canada is funded by the Canadian Space Agency, and contracted to the University of Calgary. Six Odin scientists from universities and HIA were selected in a nation-wide Canadian competition.

Odin was launched in 2001. The five mm/submm bands are centred on 119, 495, 548, 555 and 571 GHz. The spatial resolution ranges from ~2 arcminutes to ~9 arcminutes. Odin's astronomical objectives included mapping H2O in several molecular clouds and comets, and searching for O2 in the ISM. It achieved the first detection of the ground-state transition of ammonia.

INTERFERENCE PROTECTION and SPECTRUM MANAGEMENT

by Ken Tapping

The spectrum management scheme for radio astronomy continues to be very active. There is the ongoing problem of dealing with new radio services, and [...] we are having to learn to live in an environment that is steadily getting worse. A major issue is to ensure that the new radio telescopes under construction, mainly as expensive, international projects, will be able to produce high-quality, scientifically valuable data over at least the expected operational lifetimes of the instruments. On one side, these efforts are being helped by the rapid pace of technical progress. Radio service operators have the means to make their systems produce fewer and weaker unwanted emissions than was possible in the past, and those who design and construct radio telescopes are developing increasingly effective interference mitigation methods. A big effort in spectrum management is going into ensuring that all those involved are willing to make a balanced investment to protect their systems and minimize the radiation of interference. On the other hand, the march of technology has come up with something that could be a major threat to radio astronomy - the unregulated implementation of systems using Ultra-Wideband (UWB) technologies. In addition to these efforts, there is a steady background of manoeuvering by various radio service operators to weaken the measures in the Radio Regulations that protect radio astronomy, since this would substantially reduce their costs in a very competitive marketplace.

Compatibility Studies: The increasing number and variety of radio sources being studied, together with the development of new and more sensitive radio telescopes, has produced a need for an on-going series of compatibility studies between radio services and radio astronomy, on a band-by-band and service-by-service basis. The International Telecommunications Union has been locked into this on-going process for a decade, and will be for the foreseeable future. Unfortunately, results so far show that there seem to be insoluble problems with protecting radio astronomy in the 2.7 GHz, 10.7 GHz and SiO(1 - 0) 43 GHz bands. That doesn't mean we have given up, just that we have to keep working. However, it underlines the need to consider the compatibility between radio astronomy and proposed new services right from the beginning, at the design phase, and not when things are complete and it's too late to change them. In turn, this requires radio astronomers to work closely with national spectrum managers and to keep informed as to what new services are on the horizon. On a more positive front, an important consequence of the compatibility studies so far has been development of interference definition criteria that are useful for those modeling the interference potential of new radio systems, and development of tools for interference assessment and modeling. [...]

New Radio Astronomy Bands: The rapid progress of technical improvements continues to open up higher frequency bands. For some time radio astronomers have had the instrumentation needed to make observations at frequencies up to and exceeding 1000 GHz (a wavelength of 300 microns). Cost-effective commercial technologies are moving into these shorter wavelength regimes. On one hand we need to find spectral space for them. On the other we need to identify scientifically-valuable bands and get them allocated for astronomical research. We were very successful in the first phase of the work, when bands were allocated between 71 and 275 GHz. The next phase, 275 - 900 GHz, is now under consideration, and there are discussions about band allocations up to 3000 GHz (100 microns).

The advent of cheap infra-red lasers and suitable means for modulating them, together with cheap, sensitive receivers, is leading to their increasing use for broad-band data links between satellites, and between satellites and the ground. This raises the issue of possible interference with astronomical observations in the infra-red bands, and even destruction of sensors. This has raised administrative problems in spectrum protection, in that so far the regulatory process has followed the evolution of radio technology to shorter and shorter wavelengths. The lasers have brought the need for spectrum management and protection into a shorter wavelength regime. How to approach this issue is still under discussion, but time is limited, because data links and astronomical facilities are already in service.

Ultra-Wideband Technologies: There is a large number of proposed systems that are based on the transmission of very low flux densities (by radio transmission standards) over very wide bands. The idea is that these signals are so weak that nobody will be interfered with, so there should be no restriction on the frequency space used. Unfortunately, this does not apply to radio astronomy. At this point it is not clear whether any foreseeable deployment of these systems (data networks, collision avoidance systems in cars, home entertainment systems, etc.) will be a significant problem to radio astronomy or not. However, if the systems come into use there will be no going back. We are therefore actively involved in studies and modeling of interference situations (Task Group 1-8). At the moment the situation seems to depend very heavily upon models for propagation in hilly and built-up areas, and upon Monte Carlo calculations. There is more to be done before we can feel comfortable with this issue. [...] The Canadian position is that although UWB devices look attractive, the case for the claim of non-interference with other services remains to be proven, and needs to be proven before we proceed further. The USA's position is strongly in favour, and is applying strong pressure on other countries. A major worry for us is the essentially uncontrollable movement of UWB devices over the border.

RFI 2004: Mitigation of interference is an issue of growing interest to radio astronomers, especially to those concerned with the next generation of radio telescopes. In 2002, the Scientific Committee on Frequency Allocations for Radio Astronomy and Space Science (IUCAF - for historical reasons) held a highly successful international workshop at the MPIfR (Bonn) on interference mitigation in radio astronomy. Today interference mitigation is of crucial importance for the Square Kilometre Array project, and a workshop, co-sponsored by the SKA Consortium and IUCAF, was added to the 2004 SKA Conference held in Penticton. This workshop, called RFI 2004, produced a lot of valuable input and discussion. One important result was the definition of provisional protection criteria for the Square Kilometre Array that are based upon the criteria in ITU Recommendation 769.

Controlled Emission Zones: Future instruments, such as the SKA, involve substantial investments. It therefore behooves us to provide the best observing conditions possible for at least the operational life of the instrument, and also access to as much of the radio spectrum as possible, including - if at all feasible - frequencies lying outside bands allocated in the Radio Regulations to radio astronomy. To achieve this, the concept of "Emission Control Zones" has been under discussion. The idea is that major instruments such as the SKA antennas will sit within a zone where transmissions are rigorously controlled. There are two facets to this idea: the first is control of ground-based and airborne transmitters, which fall within the jurisdiction of the country hosting the instrument, and the second is transmitters on spaceborne platforms, which do not. This subject is under intense discussion within the ITU.

Solar Radio Monitoring: For historical reasons, the 10.7 cm Solar Radio Flux, one of the best indices of solar activity we have, is measured at 2800 MHz. This frequency lies within a band allocated to radiolocation, not radio astronomy. Unfortunately, the consistency of a record covering more than 50 years would be largely destroyed if the measurements were to be moved in frequency to a band allocated for radio astronomical use. The nearest band is the 2700 MHz radio astronomy band. However, in addition to the argument already made, protection of this band is problematic too. Until now, the 10.7 cm Solar Radio Flux has been protected informally, by a radio community that uses it very heavily. In the light of growing pressures on the spectrum, we are working nationally to achieve a more formal protection that will ensure long-term viability for the programme.

Possible Erosion of Radio Astronomy Protection: With many radio services fighting for frequency space in a very competitive market, there is an on-going effort to force radio astronomers to continuously re-justify the protection measures needed. Some proposals seek to erode these levels a dB or so at a time. However, there is currently extant a proposal to relax the limits by some 60 dB (106 in power, 103 in field strength). This would essentially destroy ground-based radio astronomy, so it is getting a lot of attention.

The OECD Initiative: The increasing influence within the International Telecommunications Union of industries involved in new and existing communications and broadcasting systems has led to greater and greater efforts being required to protect radio astronomy. There have been proposals that to protect radio astronomy in this changing environment, there is a need for another discussion forum and channel into the spectrum management process. Accordingly, a committee within the OECD has been discussing the problem of ensuring protection for new, major radio astronomical facilities, and has produced a very useful report on the subject. However, the OECD provides a discussion forum only; it provides no shortcut through the spectrum protection process. In the end, by international treaty, the ITU is where the spectrum management process happens, and with billions of international dollars being at stake with the new radio systems, this will remain the case. Canadian Content: In general, our approach to spectrum management and protecting observatories has been from the bottom up, rather than top down. Through the efforts of working with local municipalities, and with our national spectrum managers in Kelowna and in Ottawa, we have an Emission Control Zone in service around the Dominion Radio Astrophysical Observatory. When new services are proposed within 100 km or so of the observatory, and there could be an interference problem, then the observatory staff and spectrum managers work together to achieve license conditions that provide adequate protection while not impeding the new service any more than absolutely necessary. This has entailed being prepared to take part in national spectrum management meetings, and in increasing the awareness of our spectrum managers to what we are trying to do. To help achieve that end, we have assembled a course, called "Radio Astronomy for Spectrum Managers", which has been presented three times in Ottawa and once in Kelowna, and CD's of the PowerPoint presentation have been distributed. So far, this approach has worked well.

We are currently participating in the discussion on site evaluation for the SKA project. Our position is that for the protection of the SKA, and for the continued protection of existing radio astronomy sites, the protection criteria for the SKA should be linked in a credible way to the existing radio astronomy protection criteria. After a lot of discussion, this concept has been accepted.

IEEE-AP / URSI NARS Meeting 2003:

A large international engineering and scientific meeting, jointly sponsored by URSI, occurred in 2003. From June 22 to 27, the IEEE International Antennas and Propagation Symposium and URSI North American Radio Science Meeting was held in Columbus, Ohio. There were 1575 papers presented and the meeting was attended by antenna engineers and radio scientists from all over the world. URSI Commission J (radio astronomy) was well represented, and 17 out of 80 papers in the seven radio astronomy sessions came from Canadians:

URSI Commission J (Radio Astronomy) Special Session Canadian Papers in Session Total Papers in Session New Millimetre-Wavelength Arrays 3 12 Square Kilometre Array 3 12 Surveys at Radio Wavelengths (e.g. CGPS) 5 12 Identification and Mitigation of Radio Frequency Interference 3 13 New Developments in Cosmology 1 12 Calibration of Radiometers 1 7 Remote Sensing in Climate Research (joint with URSI commission F) 1 12

Radio astronomy is a science which is driven by technical advancement, and this was an important meeting for instrumentation development in radio astronomy. Canada has a strong reputation in radio astronomical instrumentation development, considerably larger than the size of its population would suggest.

=============================================================

PS: This article has been edited for the web. Web editor's notes are shown thus [...]