URSI Commission J (Radio Astronomy) Report to CNC
June 2005
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 URSI and the conferences which URSI organizes form an important means of communication among the world's radio astronomers, and between the world's radio astronomers and the other users of the electromagnetic spectrum. Commission J of URSI is mandated (i) to promote the technical means of radio astronomical observations and data analysis, (ii) to support activities to protect radio astronomy from harmful interference, and (iii) to observe and interpret celestial radio emissions. Because Canadian radio astronomers are deeply committed to developing the world's next generation of radio astronomical instrumentation, and also because radio astronomical access to the electromagnetic spectrum is increasingly threatened, it is important that they continue to be involved in URSI. Canadian technical radioastronomical expertise resides primarily within the Herzberg Institute of Astrophysics, but Canadian astrophysical expertise and activity extends into many large and small Canadian universities. The membership of Canadian URSI Commission J is divided roughly 3/4 - 1/4 between members who themselves make observations with radio telescopes or interpret radio data for astrophysical purposes, and those whose interests are purely technical. On the other hand, roughly a third of the astrophysically-oriented members are also active in technical improvements. Thus a quarter of the members belong in both the technical and astrophysical camps, and are a powerful force for advancement of the field. Many of these members, who are technically expert but whose innovations are driven by scientific needs, work within HIA and are widely respected within Canada and in the world astronomical community. RADIO ASTRONOMICAL FACILITIES A. ALMA and EVLA Up to 5 terabytes of data per day are expected from ALMA. The four main ALMA science themes are galaxies and cosmology, star and planet formation, stars and their evolution, and solar systems near and far. Amongst other capabilities, ALMA is expected to reveal motions of material in absorption against circumstellar disks, detect photospheric emission from a large number of normal stars, reveal detailed structure in the envelopes of evolved stars, image volcanic plume evolution on Io and winds on Mars and Venus, image gas streaming from cometary nuclei, reveal the detailed structure of star-forming clouds in other galaxies, and provide spatially and spectroscopically resolved images of the most interesting galaxies in less than an hour each. Japan officially joined the ALMA project in September 2004 and will provide a compact array and its correlator, with three receiver bands. The ALMA project is now under-going rebaselining. Tests of two 12m prototype antennas from Alcatel/EIE and Vertex/RSI were apparently finished at the VLA site in New Mexico in May, 2004, and the bids for construction of production antennas were then evaluated. However, procurement of antennas has been delayed, and testing was later resumed to address remaining technical issues including repetitive fast switching. Progress at HIA (Victoria) on the Band 3 (84 - 116 GHz) Receiver Project has been good. Measurements on Cartridge #1 gave excellent results for SSB noise, image rejection, cross-polarization, gain saturation, gain stability, and IF output power and gain flatness. In addition the HIA cryogenic HEMT 4-8 GHz IF amplifier design has excellent performance and may be used in other ALMA bands. The first complete ALMA front end, which has four cartridges in a single dewar, has now been assembled. The ALMA baseline correlator design has also been altered to give more flexibility and higher resolution in the widest bandwidth. Canada's participation in the EVLA Project 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. Phase I of the Expanded Very Large Array (EVLA) Project, which will increase the sensitivity of the VLA by an order of magnitude, is now in its fourth year. In Phase II the resolution will also be increased by an order of magnitude. The VLA will operate continuously throughout the upgrade, and the WIDAR (Wideband Interferometric Digital ARchitecture) correlator will be brought into operation in stages. Progress on the design of the EVLA correlator at HIA (Penticton) is going well; studies on the optimum chip technology were completed and bids were received from four companies. A contract has been placed for the design and fabrication of the new correlator chip, and prototype boards are being built. An on-sky test of a prototype correlator is expected in early 2006. The WIDAR concept originated within HIA (Penticton), and its extremely flexible design will permit it to accommodate real-time data from the EVLA and disk-recorded data from the Very Long Baseline Array, with great flexibility in the use of subarrays of antennas. B. SKA/CLAR: The Square Kilometre Array is an international project of very large scale with the objective of building a cm/dm-wavelength sparse aperture synthesis radio telescope array offering angular resolution of milliarcseconds and collecting area of 106 m2. Its very large collecting area will provide great sensitivity for spectroscopy of weak or rapidly time-varying sources, spectroscopic imaging of low-brightness emission, pulsar and magnetar observations, etc.. Countries involved are Australia, Canada, China, India, Italy, Netherlands, South Africa, UK, USA, and a European SKA consortium. Canada has played a leading astrophysical and engineering role in the SKA enterprise since its inception, and is an exponent of the "large-A small-N" approach requiring a relatively small number of large-area antennas, which is antipodal to the "small-A large-N approach" requiring a very large number of small-area antennas, such as 4400 paraboloids of 12m diameter. Since multiple beams must be placed on the sky simultaneously to achieve a wide field of view in the high-resolution synthesised images (e.g. 1-degree diameter at a 21cm wavelength), a "small-A large-N" design would entail a huge real-time signal processing capability and a large maintenance overhead which would be expensive, whereas the Canadian approach assumes that it will soon be possible to construct relatively few large collecting area elements at low cost per m2. Contenders in the antenna technology competition within the international SKA consortium are small paraboloids (e.g. 12m diameter), aperture arrays with no moving parts (e.g. fixed printed-circuit tiles), large line-fed cylindrical reflectors (e.g. 110m x 15m), large paraboloidal reflectors with multiply- actuated segmented surfaces (e.g. 200m diameter) using natural Karst topography, and large (e.g. 200m diameter) offset-fed multiply-actuated segmented paraboloids of long focal length constructed very close to level ground (Large Adaptive Reflectors, or LARs). The LAR concept originated with an HIA scientist and is being developed by an NRC/university/industry consortium within Canada. Its long focal length and large diameter require that the focal plane array feed package be suspended from a multiply tethered aerostat whose position relative to the reflector will change with the desired telescope pointing, while the shape of the reflector is altered with ground-mounted hydraulic actuators in real time to produce the required section of the parent paraboloidal figure. Work is underway at DRAO and other institutions within the Canadian LAR consortium to design and test prototypes of key parts of the LAR technology. The scientists involved are convinced that the cost per m2 of the telescope can be kept below ~1000 US$ without compromising antenna efficiency across the required frequency range (1 to 25 GHz) and without excessive maintenance and operating costs. The sole function of the aerostat in the LAR concept is to put tension on the tethers, giving stiffness to the telescope structure, while the focal plane array feed and receiver package rides at the nearly motionless "confluence point" where the tethers come together. From the confluence point, a single tether (a "leash") runs up to the aerostat, thus decoupling the slow movements of the aerostat from the confluence point. A one-third-scale multiply tethered helium aerostat is being tested at DRAO. Several triple-tether flights have been performed, with an instrument platform located at the confluence point. The desired 3-dimensional position of the instrumentation package can now be entered as input, and the system responds in real time. The instrument platform collects data with a differential GPS receiver, an electronic compass, tiltmeters, a wind speed and direction measurement system, and load cells for measuring tension in the tethers. With the aerostat at 300m altitude and the instrument platform at 150m altitude, the stability of the confluence point is found to be commensurate with GPS accuracy. With a full-scale aerostat the system will be much stiffer (the lift will be many times larger), and stability will also increase because the aerostat will no longer be located in the atmospheric boundary layer near the ground. Work is also underway at DRAO on other key components of the LAR. One is a two-dimensional array of broadband Vivaldi antennas for use as a focal plane array. Digital beamforming experiments are planned with this prototype feed array. Another key component is the actuated surface of the reflector, which must be rugged, accurate, lightweight, and low-cost. A prototype hydraulically-actuated segment of the reflector is now operating at DRAO. The ultimate proof of the Large Adaptive Array concept for the SKA will be to construct and operate a full-scale LAR of 300m diameter as a stand-alone radio telescope of huge sensitivity and great versatility. This innovative single-dish telescope design is known as the Canadian Large Adaptive Reflector, or CLAR, and in its own right it will be a world-class instrument capable of out-performing the Effelsberg 100m telescope, the new 110m Green Bank Telescope, and the Arecibo Telescope. (It should be mentioned here that the Arecibo spherical reflector is under-illuminated, i.e. its aperture is strongly vignetted; it functions as roughly a 200-metre telescope with limited range in zenith angle.) A 300m-diameter CLAR would therefore in fact be the world's largest single-dish telescope and would offer immense versatility because of its huge sensitivity, wide range in zenith angle, reasonably high resolution ( < 3 arcminutes at 21cm wavelength), wide instantaneous field of view (achieved with the focal plane array feed), extremely flat spectroscopic baselines (because it is offset-fed), broadband capability (Vivaldi focal plane arrays are expected to have 3:1 bandwidth or more), and correctable instrumental polarization (cross-polarization leakage removed during beam formation with the focal plane array outputs). CLAR will have the capability to make significant progress in several key areas of astrophysics and cosmology, and a number of areas of astrophysical research in Canada will be enormously stimulated. Among many other capabilities, CLAR will be able to investigate the distribution of matter in the Universe by mapping the distribution of galaxies in redshift out to z ~ 4, detect the "cosmic web" of HI in the intergalactic gaseous network, map weak magnetic fields in clusters and superclusters of galaxies (possibly the "seed field" for galactic fields), study High Velocity Clouds in groups of galaxies to ascertain whether HVC's originate in primordial dark matter haloes or are tidal debris from galactic interactions, detect masers in the accretion disks of supermassive black holes and in shocks driven by jets and winds, reveal the kinematics and evolution of low-density extended HII regions in our Galaxy using radio recombination lines, reveal magnetic field strengths and directions within molecular clouds from large scales down to 0.1 pc scale through observations of OH and CCS, detect pulsar wind nebulas and cavities formed in the ISM by supernova precursors, and study slowly varying and flare-type radio emissions from nearby solar-type main sequence stars. CLAR will be the world's most powerful telescope for studies of neutron stars, offering unparalleled opportunities for investigation of the most extreme conditions in the observable Universe and for observational tests of basic scientific theories such as general relativity and quantum electrodynamics. C. JCMT A hugely important development is that with its suite of fast new instruments with wide fields of view, the JCMT is about to undertake large-scale survey-mode observations. SCUBA-2 is a bolometer array camera which will bring 40 X 32 - pixel observing to the JCMT, imaging the 450 micrometer and 850 micrometer continuum simultaneously. The images will cover a field of view greater than 50 arcmin2. With its high sensitivity, SCUBA-2's imaging speed will be far greater than that of the current SCUBA camera. FTS-2 is a Fourier transform spectrometer which will operate in conjunction with SCUBA-2, covering nearly a quarter of the field of view. High-sensitivity polarization imaging with SCUBA-2 will be made possible by the POL-2 wide-field polarimeter. This is an important development because large-scale polarimetric images of low-density material in molecular clouds are required to show how the magnetic field in dense star-forming regions is connected to the magnetic field threading the rest of the cloud. For spectroscopic imaging, the HARP-B focal-plane array and the HIA-developed ACSIS correlator will offer 16-pixel observing in the 325 - 375 GHz band with twenty spectra per second in each pixel. ACSIS and HARP-B have now been delivered to Hawaii, and the first spectrum has now been observed. Two of the surveys to be undertaken by the JCMT are the Gould's Belt Legacy Survey and the JCMT Legacy Survey of the Galactic Plane: (a) The Gould's Belt Legacy Survey has the objective of covering all star-forming regions within 500 pc of the Sun, from starless cores to protostars. This project will require observing ~5000 sources with SCUBA-2, HARP-B, and POL-2. The scientific goals are to determine protostellar lifetimes and accretion rates, determine the origin of the initial mass function, reveal all scales of physical structure from cores to clouds, investigate the kinematics of cores and filaments, and elucidate the role and geometry of the magnetic field in star formation. In this work, HARP-B will observe 12CO, 13CO, and C18O in the J = 3 - 2 transition. (b) The JCMT Legacy Survey of the Galactic Plane (JPS) has the objective of 512 square degrees, comprising 10-degree < l < 250-degree, |b| < 1-degree, plus the W3 - 4 - 5 region to b < 2-degree, and NGC 7538 within -4-degreee < b < 3-degree. The scientific goals are to establish the evolutionary sequence for massive star formation, determine how the star-forming environment is regulated, reveal the structure of molecular clouds and the formation process of molecular clouds, and to reveal Galactic structure. For the JPS, the instruments used will be SCUBA-2 (850 and 450 micrometers), HARP-B, and FTS-2. The Gould's Belt and Galactic Plane surveys will both be pathfinders for ESA's submm and far-infrared Herschel Space Observatory (which will carry two instruments, SPIRE and HIFI, in whose development Canadians are participating), and for ALMA. D. DRAO Galactic Plane Survey: Both the Synthesis Telescope and the 26-metre telescope are being used for work essential to the ongoing Canadian Galactic Plane Survey (CGPS), which is a key project in the International Galactic Plane Survey (IGPS). The IGPS also includes the VLA Galactic Plane Survey (VGPS) and the Southern Galactic Plane Survey (SGPS). Together these three surveys are covering ninety percent of the disk of the Galaxy. The CGPS is actually a suite of arcminute-resolution surveys of atomic gas (DRAO spectroscopic 21cm HI images), molecular gas (FCRAO spectroscopic CO images), and dust (CITA 12 & 25 mircometer Mid-Infrared Galaxy Atlas, and Caltech 60 & 100 micrometer Infrared Galaxy Atlas), plus DRAO images of synchrotron and thermal emission at 408 and 1420 MHz. All these images are mosaiced to yield very-large-field images which are revealing structures in the ISM which have not been discovered in any previous observations with any telescope, either (a) because the angular resolution was inadequate and the structure (e.g. filamentary structure) was washed out by the beamsize, or (b) because the field of view was too small to reveal the feature. Salient examples of such structures in the ISM are those being revealed in the 1420 MHz continuum polarization mosaics from the Synthesis Telescope. The 26-metre telescope, besides contributing the crucial low-order Fourier components to the ?21cm spectroscopic HI mosaics, is also proving indispensable data to the 1420 MHz polarization mosaics. For these mosaics, the Stokes parameter images from the DRAO Synthesis Telescope will be combined with the Effelsberg Medium-Latitude Polarization Survey made at 1.4 GHz with the 100-metre telescope of the Max Planck Institut fur Radioastronomie (MPIfR). However, the 100-metre data, which are taken over 10-degree x 10-degree -fields, must themselves be corrected for unknown zero-levels at the four corners of each 10-degree field. As a result, the MPIfR and DRAO have embarked on a well-calibrated, Nyquist-sampled polarization survey of the northern sky using the DRAO 26-metre telescope. To this end the instrumental polarization of the 26m telescope is being carefully investigated with electromagnetic simulation and measurements. With the addition of a wide-band front-end and polarizer for the 26m telescope, an intriguing spin-off will be Faraday-rotation mapping capability for the 26m telescope, and ultimately Faraday tomography of the ISM. The processes that govern the evolution of very distant galaxies are of great interest to cosmologists and astronomers today. However, a galaxy's ISM is an evolving milieu in which successive generations of stars are formed and age, while the milieu itself is altered structurally, dynamically, chemically, and thermally. Unfortunately, these processes are still poorly under-stood. Because of our unique vantage point within the Milky Way Galaxy, studies of all aspects of its structure and its ISM must be carried out over the full range of spatial scales, from the sub-parsec scale of stellar formation to the kiloparsec scale of spiral arms. These studies motivate the Galactic Plane Survey work which is underway at DRAO now. Ongoing improvements in the system temperature of the Synthesis Telescope from antenna and receiver modifications have already resulted in nearly twenty percent increase in its sensitivity. The telescope is primarily engaged in Galactic Plane survey observations, but has lately also been directed toward higher-latitude regions in targetted observations. Two examples of these are (a) a mosaic of part of the Taurus Molecular Cloud star-forming region, and (b) the DRAO Planck Deep Field, for precise deconvolution of Galactic "foreground" radiation from the Cosmic Microwave Background, and to reveal the structure, energetics, and physical states of matter in the Galactic Halo. [...] Conferences: three important conferences were held at Penticton in 2004 by the staff of DRAO. These were the international SKA meeting, an international RFI workshop, and the 2004 meeting of the International Galactic Plane Survey. The SKA conference, called SKA2004, was an international meeting of astronomers and engineers to discuss and refine the science goals and telescope concepts for the Square Kilometre Array. Special sessions were held for leading SKA science areas (e.g. evolution of galaxies and large scale structure), the convergence of telescope concepts for this very large aperture synthesis instrument, and pivotal technology and system design issues. An Engineering forum consisted of invited and contributed presentations related to engineering development for the SKA. RFI2004 was a workshop dedicated to Radio Frequency Interference and Interference Mitigation, sponsored jointly by the International SKA consortium and IUCAF (Inter-Union Committee for the Allocation of Frequencies). A large fraction of the SKA2004 attendees also participated in RFI2004. E. Radio Astronomy in Space Space VLBI: Canada was until late 2003 an important participant in the VLBI Space Observatory Program (VSOP) which involved the Japanese HALCA 8m orbiting telescope and several ground telescopes. This participation occurred through use of the Canadian S2 Space VLBI correlator designed, built, and operated at DRAO. VSOP Survey data reduction and analysis continued thereafter at the University of Calgary. Canadians are now planning to participate in future space VLBI missions including VSOP-2 and RadioAstron. VSOP-2 is a next-generation space VLBI mission planned by Japan. Improvements in resolution and sensitivity by orders of magnitude over the VSOP mission are anticipated with higher observing frequencies, cooled receivers, increased bandwidths, and a larger orbiting telescope. Use of phase-referencing, requiring rapid slewing by the orbiting antenna, would improve the sensitivity even further. The Russian Federal Space Agency has recently announced that it will launch the RadioAstron orbiting VLBI telescope in 2007. Canadian radio astronomers have been involved in this international project (Russia, USA, Canada, Finland, ESA, India, Australia, Ukraine) for many years. The RadioAstron project has been greatly delayed by political changes, but is now a top science mission of the Russian Space Agency. The main objective will be observation of regions of ultra-high brightness temperature near massive black holes with micro-arcsecond resolution. This high resolution will be achieved by orbiting the 10m antenna with an apogee near 340,000 km and observing at frequencies as high as 22 GHz. It is expected that general relativistic effects such as warped space-time structure near black holes will be detectable. The formation of radio jets will also be studied in detail. BLAST (Balloon-borne Large Aperture Submillimetre Telescope) is a 2-metre far-infrared telescope, using high-sensitivity cryogenic bolometer arrays and observing at 250, 350, and 550 micrometers. The 2m mirror primary is spherical but is combined with a 40cm correcting secondary. BLAST is intended to survey Galactic star formation regions and high-redshift galaxy formation, and may also image high velocity clouds within our Galaxy. The project is joint among USA, Canada, UK, and Mexico. Canadian involvement in BLAST is centred at University of Toronto, UBC, and AMEC Dynamic Structures Ltd.. Canada designed and built the gondola, the pointing control system, and other electronic equipment. The window of opportunity for the launch from Kiruna, Sweden, is May 20 - June 30, 2005, and the flight could last a week at 130,000 ft altitude. It is hoped that the flight will end near Inuvik. ODIN: The Odin Submillimeter Satellite, a joint astronomy/aeronomy mission among Sweden, Canada, France and Finland, was the second submm telescope in space. It consists of a 1.1m telescope and four submm receivers centred on 606, 547, 540, and 525 micrometers. There is also a receiver at 2.52 mm for the ground-state transition of O2. The angular resolution at the shortest wavelength is ~2 arcminutes. Odin has been operating for over four years. Besides observations of H2O and O2, Odin has the unique capability, because its receivers are tunable, of taking spectra throughout the submm window. Activity in the Odin project is centred at the University of Calgary. ====================================================== INTERFERENCE PROTECTION and SPECTRUM MANAGEMENT by Ken Tapping Introduction The environment in which we have to do radio astronomy continues to get more challenging. In addition to our needing far more sensitive instruments and more demanding observing methods, the rapidly growing list of new radio services is placing increasing pressure on the spectrum. There has to be space to fit all these new services in there somewhere. Because new allocations have to be spliced into a hard-to-change spectrum allocation scheme that has been evolving over many decades, many of the new allocations are unavoidably non-optimal for avoiding interference with other users of the spectrum, particularly radio astronomy. A further consideration is that the instruments needed for front-line radio astronomical research tend to be large, expensive multinational projects, and it is necessary to ensure that these instruments will be able to work to their design specifications for at least the specified project lifetime. This means having a long-term approach to interference control at these instruments. To some extent the steady progress in signal processing and interference mitigation is helping us to accommodate more challenging interference environments, but this is not an argument for relaxing our efforts to protect the spectrum. Band-by-Band Studies Over more than a decade, the International Telecommunication Union has operated a series of Task Groups having the mandate to look at the spectrum usage by radio services operating transmitters and to assess interference risks to radio astronomers making observations in frequency bands allocated to radio astronomical use. The objective is to find the interference risks and to identify mitigation measures that could be applicable. The continuing appearance of new radio services and allocation of new radio astronomy bands make this an on-going task. Some useful research has been done. There has been some use of the results in avoiding interference issues. However, [...] the most useful output of these studies may have been a set of standard tools for identifying potential interference situations and standardized criteria for clearly identifying problems that require action, and for their incorporation into the International Radio Regulations.. Data Transmission Over Power Lines For some years there has been a growing interest in using the distribution networks used by electrical power utilities for data communication. The attraction is that these networks already exist almost everywhere. The downside is that they are not designed for radio frequency communication. The intention is to transmit broad-band digital signals at frequencies up to tens of MHz. Mismatch, and resistive and radiation losses are likely to be significant. One company suggested that this could easily be remedied by using "plenty of power". The issue of emission by the power lines and harmonic generation in poor joints, corrosion, and degraded insulators have raised a lot of questions and skepticism. Pending any rulings on this issue, the International Telecommunications Union has requested studies be made. Modelling the emission with reasonable accuracy is difficult. Canada has built a technology tester and is evaluating it. Some estimates suggest the emissions from the lines might be a significant interference source more than 400 km from the line, and perhaps detectable over the whole world; others suggest they will not be a problem. The USA is implementing these systems already. The Canadian point of view is that with many more effective communications options being available, communications over power lines will have limited use. Space Radio Astronomy Radio astronomy from space platforms offers access to frequencies that do not penetrate to the Earth's surface and baselines for interferometry experiments that are not possible using only ground-based radio telescopes. The International Telecommunications Union has agreements indicating that the L2 Lagrange Point would be a good place for a Radio Astronomy Reserve. The differences between space and ground-based radio astronomy are making it necessary to review whether there should be specific protections and allocations for this area of radio astronomy. Emission Control Zones Instruments like ALMA and the Square Kilometre Array may reach their potential over the planned lifetime only if they are embedded in a zone where they are protected against interference, hopefully with exemptions that provide additional spectrum access. In Canada addressing this problem for national facilities such as the Dominion Radio Astrophysical Observatory is through an "emission control zone", where the local observatory staff work with local and national spectrum managers to ensure that interference problems are identified and avoided while minimizing any inconvenience to radio services that are not interference threats. There are proposals for stronger, more rigid arrangements, but the Canadian position is that these situations are best dealt with by organizations working together. New Spectrum for Radio Astronomy Technical developments are rapidly pushing viable radio receivers to higher and higher frequencies. The International Telecommunications Union is now looking at the allocation of the spectrum to 3,000 GHz. With the wealth of molecular lines at such frequencies, radio astronomers are in the process of identifying and prioritizing bands that would be good to have allocated for radio astronomical use. Infra-red lasers are now being used for inter-satellite communication and are proposed for space-Earth links and even for deep space applications. These could have serious ramifications for facilities such as GEMINI which are heavily used for observations in the infra-red. This is receiving useful discussion at the ITU but there is as yet nothing approaching allocations or protection measures. Time is limited, because data links and astronomical facilities are already in service. Ultra-Wideband Technologies A number of countries are now implementing systems that are based upon 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. The International Telecommunication Union has set up a Task Group to look at the compatibility of UWB. Modelling these systems is complicated, and is very dependent upon calculations of propagation in hilly and built-up areas, and upon Monte Carlo calculations. 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. However, the USA is already deploying UWB systems, and is applying strong pressure to Canada and other countries. 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 at DRAO. 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 (1 million in power, 1000 in field strength). This would essentially destroy ground-based radio astronomy. The radio astronomers have reacted officially to this proposal within the ITU, and a dialogue is now active. 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. In an effort to ensure better discussion of radio astronomy issues in this changing environment, especially with respect to ensuring the major new radio telescopes such as the SKA and ALMA, another forum has been developed within the OECD. However, the OECD provides a discussion forum only; it provides no shortcut through the spectrum protection process. A very useful report has been produced and is being taken to the International Telecommunications Union by IUCAF for use in radio astronomy protection negotiations. The OECD forum has no legislative power. That remains exclusively in the hands of the ITU. Canadian Content Over the last year, Canada has continued to work vigorously nationally and inter-nationally on issues pertaining to the protection of radio astronomy. At a local and national level this has involved work with local and national spectrum managers. Canada continues to lobby internationally for an extensive evaluation of the benefits and impacts of new systems such as ultra-wideband technologies and data communication over power lines before they are put into widespread service. Canada also proposed international discussions about the status of space radio astronomy. For example, if the inverse square law is an important part of protecting ground-based radio telescopes from satellites, how does one approach protection of radio telescopes on spacecraft, which are much closer to the satellite transmitters? It has been possible to get some recognition that the most effective way to protect facilities from interference is to provide adequate protection while not impeding the new service any more than absolutely necessary. This is the best way to maintain a good atmosphere for dealing with problems on an on-going basis. Example (D. Routledge) The JPL-Colorado State CloudSat cloud-mapping spacecraft arrived at Vandenburg Air Force Base on May 2, 2005, to begin final preparations for launch on a Delta II vehicle. It will fly in a near-polar orbit with a 99 minute period at 705 km altitude, carrying a pulsed 1.8 kW, 94 GHz radar with a nadir-pointing high-gain antenna. The www.iucaf.org/CloudSat website states that if CloudSat passes over a radio telescope using SIS receivers, the receivers will likely saturate regardless of where the telescope is pointing, and the receivers could be burned out if CloudSat crosses the main beam. CloudSat will fly overhead, or nearly so, at a substantial fraction of the world's observatories. It should be noted that the ALMA Band 3 (84-116 GHz) receivers could be directly affected. NASA has recently placed contracts for a later spacecraft which will broadcast downward at 14 and 36 GHz and also scan off-axis.=============================================================
PS: This article has been edited for the web. Web editor's notes are shown thus [...]