The Russian Academy of Sciences and Federal Space Agency, together with the participation of many international organizations, worked toward the launch of the RadioAstron orbiting space observatory with its onboard 10-m reflector radio telescope from the Baikonur cosmodrome on July 18, 2011. Together with some of the largest ground-based radio telescopes and a set of stations for tracking, collecting, and reducing the data obtained, this space radio telescope forms a multi-antenna ground-space radio interferometer with extremely long baselines, making it possible for the first time to study various objects in the Universe with angular resolutions a million times better than is possible with the human eye. The project is targeted at systematic studies of compact radio-emitting sources and their dynamics. Objects to be studied include supermassive black holes, accretion disks, and relativistic jets in active galactic nuclei, stellar-mass black holes, neutron stars and hypothetical quark stars, regions of formation of stars and planetary systems in our and other galaxies, interplanetary and interstellar plasma, and the gravitational field of the Earth. The results of ground-based and inflight tests of the space radio telescope carried out in both autonomous and ground-space interferometric regimes are reported. The derived characteristics are in agreement with the main requirements of the project. The astrophysical science program has begun.

Parabolic reflectors (dishes) are the most general purpose, flexible antennas used in radio astronomy, typically able with multiple feeds to cover two orders of magnitude in frequency. The SKA requirements will push the limits of dish design for decimetre wavelengths beyond that of any existing dishes. The SKAs sensitivity as well as its wide-field imaging requirements push performance limits, while the need to produce and deploy thousands of dishes in an array spanning continental baselines push cost and fabrication limits. This paper will discuss SKA requirements and a combination of techniques being brought to bear on this design problem.

The Square Kilometre Array (SKA) is intended as the next-generation radio telescope and will address fundamental questions in astrophysics, physics, and astrobiology. The international science community has developed a set of Key Science Programs: (1) Emerging from the Dark Ages and the Epoch of Reionization, (2) Galaxy Evolution, Cosmology, and Dark Energy, (3) The Origin and Evolution of Cosmic Magnetism, (4) Strong Field Tests of Gravity Using Pulsars and Black Holes, and (5) The Cradle of Life/Astrobiology. In addition, there is a design philosophy of "exploration of the unknown," in which the objective is to keep the design as flexible as possible to allow for future discoveries. Both a significant challenge and opportunity for the SKA is to obtain a significantly wider field of view than has been obtained with radio telescopes traditionally. Given the breadth of coverage of cosmic magnetism and galaxy evolution in this conference, I highlight some of the opportunities that an expanded field of view will present for other Key Science Programs.

We present a new large-scale survey of the J = 3-2 (12)CO emission covering 4.8 deg(2) around the Rosette Nebula. The results reveal the complex dynamics of the molecular gas in this region. We identify about 2000 compact gas clumps having a mass distribution given by dN/dM similar to M(-1.8), with no dependence of the power-law index on distance from the central O stars. A detailed study of a number of the clumps in the inner region shows that most exhibit velocity gradients in the range 1-3 km s(-1) pc(-1), generally directed away from the exciting nebula. The magnitude of the velocity gradient decreases with distance from the central O stars, and we compare the apparent clump acceleration with a photoionized gas acceleration model. For most clumps outside the central nebula, the model predicts lifetimes of a few 10(5) yr. In one of the most extended of these clumps, however, a near-constant velocity gradient can be measured over 1.7 pc, which is difficult to explain with radiatively driven models of clump acceleration.As well as the individual accelerated clumps, an unresolved limb-brightened rim lies at the interface between the central nebular cavity and the Rosette Molecular Cloud. Extending over 4 pc along the edge of the nebula, this region is thought to be at an earlier phase of disruption than the accelerating compact globules.Blueshifted gas clumps around the nebula are in all cases associated with dark absorbing optical globules, indicating that this material lies in front of the nebula and has been accelerated towards us. Redshifted gas shows little evidence of associated line-of-sight dark clouds, indicating that the dominant bulk molecular gas motion throughout the region is expansion away from the O stars. In addition, we find evidence that many of the clumps lie in a molecular ring, having an expansion velocity of 30 km s(-1) and radius 11 pc. The dynamical time-scale derived for this structure (similar to 10(6) yr) is similar to the age of the nebula as a whole (2 x 106 yr).The J = 3-2/1-0 (12)CO line ratio in the clumps decreases with radial distance from the exciting O stars, from 1.6 at similar to 8 pc distance to 0.8 at 20 pc. This can be explained by a gradient in the surface temperature of the clumps with distance, and we compare the results with a simple model of surface heating by the central luminous stars.We identify seven high-velocity molecular flows in the region, with a close correspondence between these flows and embedded young clusters or known young luminous stars. These flows are sufficiently energetic to drive gas turbulence within each cluster, but fall short of the turbulent energy of the Rosette giant molecular cloud by two orders of magnitude.We find 14 clear examples of association between an embedded young star (as seen by Spitzer at 24 mu m) and a CO clump in the molecular cloud facing the nebular. The CO morphology indicates that these are photoevaporating circumstellar envelopes. CO clumps without evidence of embedded stars tend to have lower gas velocity gradients. It is suggested that the presence of the young star may extend the lifespan of the externally photoevaporating envelope.

This paper describes a new Heterodyne Array Receiver Programme (HARP) and Auto-Correlation Spectral Imaging System (ACSIS) that have recently been installed and commissioned on the James Clerk Maxwell Telescope (JCMT). The 16-element focal-plane array receiver, operating in the submillimetre from 325 to 375 GHz, offers high (three-dimensional) mapping speeds, along with significant improvements over single-detector counterparts in calibration and image quality. Receiver temperatures are $\sim$120 K across the whole band and system temperatures of $\sim$300K are reached routinely under good weather conditions. The system includes a single-sideband filter so these are SSB figures. Used in conjunction with ACSIS, the system can produce large-scale maps rapidly, in one or more frequency settings, at high spatial and spectral resolution. Fully-sampled maps of size 1 square degree can be observed in under 1 hour. The scientific need for array receivers arises from the requirement for programmes to study samples of objects of statistically significant size, in large-scale unbiased surveys of galactic and extra-galactic regions. Along with morphological information, the new spectral imaging system can be used to study the physical and chemical properties of regions of interest. Its three-dimensional imaging capabilities are critical for research into turbulence and dynamics. In addition, HARP/ACSIS will provide highly complementary science programmes to wide-field continuum studies, and produce the essential preparatory work for submillimetre interferometers such as the SMA and ALMA.

We describe algorithms that detect 21 cm line H I self-absorption (HISA) in large data sets and extract it for analysis. Our search method identifies HISA as spatially and spectrally confined dark H I features that appear as negative residuals after removing larger scale emission components with a modified CLEAN algorithm. Adjacent HISA volume-pixels (voxels) are grouped into features in (l,b,v) space, and the H I brightness of voxels outside the three-dimensional feature boundaries is smoothly interpolated to estimate the absorption amplitude and the unabsorbed H I emission brightness. The reliability and completeness of our HISA detection scheme have been tested extensively with model data. We detect most features over a wide range of sizes, line widths, amplitudes, and background levels, with poor detection only where the absorption brightness temperature amplitude is weak, the absorption scale approaches that of the correlated noise, or the background level is too faint for HISA to be distinguished reliably from emission gaps. False detection rates are very low in all parts of the parameter space except at sizes and amplitudes approaching those of noise fluctuations. Absorption measurement biases introduced by the method are generally small and appear to arise from cases of incomplete HISA detection. This paper is the third in a series examining HISA at high angular resolution. A companion paper (Paper II) uses our HISA search and extraction method to investigate the cold atomic gas distribution in the Canadian Galactic Plane Survey.

Cost effective, new antenna technology is required to build the large collecting area being planned for the next generation of radio telescopes. The Large Adaptive Reflector (LAR) is a novel concept being developed in Canada to meet this challenge. A prototype with a 200-350m diameter reflector, operating up to 2 GHz with a bandwidth of 750 MHz is planned. With a collecting area up to ~10% of the planned SKA, and an array feed capable of imaging a 0.3 deg^2 field-of-view, the prototype would address a number of the most compelling questions in modern astrophysics.

We present a 21 cm line H I self-absorption (HISA) survey of cold atomic gas within Galactic longitudes l = 75° to 146° and latitudes b = -3° to +5°. We identify HISA as spatially and spectrally confined dark H I features and extract it from the surrounding H I emission in the arcminute-resolution Canadian Galactic Plane Survey (CGPS). We compile a catalog of the most significant features in our survey and compare our detections against those in the literature. Within the parameters of our search, we find nearly all previously detected features and identify many new ones. The CGPS shows HISA in much greater detail than any prior survey and allows both new and previously discovered features to be placed into the larger context of Galactic structure. In space and radial velocity, faint HISA is detected virtually everywhere that the H I emission background is sufficiently bright. This ambient HISA population may arise from small turbulent fluctuations of temperature and velocity in the neutral interstellar medium. By contrast, stronger HISA is organized into discrete complexes, many of which follow a longitude-velocity distribution that suggests that they have been made visible by the velocity reversal of the Perseus arm's spiral density wave. The cold H I revealed in this way may have recently passed through the spiral shock and be on its way to forming molecules and, eventually, new stars. This paper is the second in a series examining HISA at high angular resolution. A companion paper (Paper III) describes our HISA search and extraction algorithms in detail.

Sharpless 170 is a diffuse HII region ionized by a single main sequence O-star located near the periphery of a small dense molecular cloud at a distance of similar to2 kpc. We describe wide-field observations of the region in the radio continuum, in HI and CO-lines, and in the far-infrared which delineate the major ionized, atomic, molecular and dust components of the gas affected by the exciting star. From the thermal continuum emission we estimate the mass of ionized gas at similar to350 M-. within a radius of similar to7 pc. The HI (lambda21 cm) and far-infrared observations show an extended low-density atomic component, of similar to 1000 M-. within an irregular boundary surrounding the ionized gas of mean radius similar to10 pc. Mean densities in the HI and HII are similar, in the range 9-16 nucleons cm(-3). CO emission shows a molecular cloud of similar to 1150 M-. within an area 6 pc x 4 pc with densities similar to2000 nucleons cm(-3). A compact infrared component coincides with the cloud. The exciting star is located on the near side of the cloud, just inside the southern periphery.Sh170 is an example of a young HII region with the ionized gas, seen in Halpha emission, streaming outward in the manner of a "champagne flow". Although the observed velocities of the HI are close to the mean velocity of the CO cloud, the morphology of the associated atomic hydrogen closely resembles that seen in the surrounds of other young HII regions which show clear evidence of expansion of their HI. We propose that much of the HI is a diffuse dissociation zone beyond the ionization front, in directions from the star within a wide annulus, approximately transverse to the line-of-sight, between the dense photon-bounded region on the far side of the star and the density-bounded ionized flow region on the near side. In this view, much of the associated atomic gas, like the ionized gas, has been eroded from the molecular cloud in a small fraction (less than or equal to10%) of the star's main sequence lifetime.

Observations of the environment of the star-forming region NGC 7129 obtained with an angular resolution of 1' in the 21 cm line of Hi are described. Two features of the image are extensively discussed: (1) a ring of H I emission about 300 in extent and (2) a relatively dense concentration of H I with unusually wide line profiles positionally coincident with the B star BD + 65degrees1638. The H I ring is consistent with photodissociation of H-2 by the interstellar UV radiation field at the surface of an extended molecular cloud in which both BD + 65degrees1638 and NGC 7129 are situated. We further show that BD + 65degrees1638 appears to be an unusual example of a "dissociating star" surrounded by an extensive region of photodissociated H-2 and accompanied by a small H II region. The derived spectral type (B2.5) and the absolute magnitude for BD + 65degrees1638 further suggest that the latter is very close to the birthline. The very young stellar age implied by the parameters of the H I region, considerably less than 10(4) yr, is discussed, and the properties of the H I region are compared with those of the prototype for this rare class of objects. We discuss both aspects within the context of star formation in NGC 7129.

We present high resolution radio continuum maps of the Galactic nebula Simeis 57 (= HS 191 = G 80.3+4.7) made with the WSRT and the DRAObservatory at frequencies of 609, 1412 and 1420 MHz. At optical and at radio wavelengths, the nebula has a peculiar ``S'' shape, crossed by long, thin and straight filaments. The radio maps, combined with other maps from existing databases, show essentially all radio emission from the peculiar and complex nebula to be thermal and optically thin. Although neither the distance nor the source of excitation of Simeis 57 are known, the nebula can only have a moderate electron density of typically n(e) = 100 cm-3. Its mass is also low, not exceeding some tens of solar masses. Peak emission measures are 5000 pc cm-6.Obscuring dust is closely associated with the nebula, but seems to occur mostly in front of it. Extinctions vary from A(V) = 1.0 mag to A(V) = 2.8 mag with a mean of about 2 mag. The extinction and the far-infrared emission at 100 microns are well-correlated.

ACSIS (Auto Correlation Spectrometer Imaging System) is a real-time data collection and reduction system intended for use with a 16 pixel receiver at the James Clerk Maxwell Telescope on Mauna Kea, Hawaii. At peak operating speed, the correlator connected to each receiver will generate an autocorrelation lag array of 8192 numbers every 50 ms, or 10.5 Mbytes of data every second. The ACSIS reduction system converts raw lag-data into calibrated radio-frequency spectra as the data are obtained. In mapping modes, these spectra are further inserted into a 3-dimenslonal data cube of image planes as a function of radio frequency. The reduction system should produce calibrated data of sufficient quality that further o-line processing is not required. Since single dish radio telescopes can observe the sky in many different ways, the reduction system has been effectively designed as a collection of high-performance programmable calculators that can be easily reconfigured for different or new observing modes. We describe the object-oriented design of the system and present some initial timing results obtained from processing synthetic data on a small Beowulf cluster of sixteen 450-MHz commodity PCs. The astronomer can view the data as it is processed by a data display that shows both the radio spectra and the contents of the gridded data cubes as they are updated.

We present high resolution radio continuum maps of the Galactic nebula Simeis 57 (= HS 191 = G 80.3+4.7) made at the Westerbork Synthesis Radio Telescope and the Dominion Radio Astrophysical Observatory at frequencies of 609, 1412 and 1420 MHz. At optical and at radio wavelengths, the nebula has a peculiar S shape, crossed by long, thin and straight filaments. The radio maps, combined with other maps from existing databases, show essentially all radio emission from the peculiar and complex nebula to be thermal and optically thin. Although neither the distance nor the source of excitation of Simeis 57 are known, the nebula can only have a moderate electron density of typically ne = 100 cm −3 . Its mass is also low, not exceeding some tens of solar masses. Peak emission measures are 5000 pc cm −6 . Obscuring dust is closely associated with the nebula, but seems to occur mostly in front of it. Extinctions vary from AV = 1.0 mag to AV = 2.8 mag with a mean of about 2 mag. The extinction and the far-infrared emission at λ100 µm are well-correlated.

ACSIS is the Auto-Correlation Spectrometer Imaging System being developed for the James Clerk Maxwell Telescope and the B-band Heterodyne Array Receiver Project (HARPB). The system has an overall processing rate of 10 MB/sec, with a parallel data-flow architecture, consisting of over 25 processors and 50 real-time tasks that are organized in a distributed concurrent and pipeline fashion. We describe the scheme used by ACSIS, and the JCMT observing system, to co-ordinate these tasks for the collection and reduction of data in real-time.

The Canadian Large Adaptive Reflector (CLAR) is a proposed prototype of a new concept for large, filled-aperture radio telescopes. The prototype would have a 300-metre aperture, working up to frequencies of at least 1.4 GHz, and would be equipped with a multi-beam phased array providing a field-of-view of 0.8deg at that frequency. The largest fully-steerable radio telescope in the world, and endowed with a large field-of-view, the CLAR will be uniquely suited for deep spectral imaging over large areas of the sky. Conducted over a period of three to four years, a CLAR Northern-Sky Survey would allow us to simultaneously: survey at arcminute scales the distribution and kinematics of the faint HI in the halo of the Milky Way and High Velocity Clouds; chart the large scale distribution of galaxies in HI out to redshift close to 1; reveal the structure and dynamics of the cosmic web responsible for wide-spread Lyman $α$ absorption systems; image the signal of the reionization of the Universe over a large area with resolution of 10's of arcminutes.

We reveal cold Galactic clouds of neutral hydrogen in unprecedented detail. Our 21 cm synthesis maps, taken from the Canadian Galactic Plane Survey, show a numerous and diverse population of H I self-absorption (HISA) features in gas outside the solar circle. These objects vary in size, shape, and contrast against the background H I. All display a high level of angular and velocity structure, and most would appear significantly diluted, if not invisible, in lower resolution H I surveys. A number of Perseus arm features remain unresolved by the 1' beam of our survey, with apparent diameters less than 0.6 pc at 2 kpc distance. The majority of HISA features we detect have no obvious 12CO emission counterparts. This suggests that either HISA is not found predominantly in molecular clouds, as has often been presumed in the past, or that CO is not a good tracer of H2. Some HISA lacking CO shows far-infrared dust emission, though whether this arises from shielded molecular gas or from diffuse atomic clouds is not clear. Constraining the gas properties of HISA remains a difficult problem, but we introduce a new method that aids this process. Our approach relates a number of physical parameters via gas law and line integral relationships and should prove powerful if the input variables are sufficiently well known. We explore the current allowed parameter ranges for three sample features of very different appearance. We find spin temperatures ≲50 K and densities ≳102 cm-3.

The Canadian contribution to the VSOP Space VLBI mission is based on the S2 recording system, a correlation centre, and a data analysis and archive centre. The S2 record/playback terminals are a low cost and reliable means for recording VLBI data and are presently distributed worldwide at 17 observatories involved in the VSOP mission. The Canadian S2 correlator is a lag-based correlator, designed specifically to handle Space VLBI signal processing. Fringe de-rotation and delay compensation are station-based, and the correlator's 24576 lag channels can be distributed in a variety of ways to accommodate both continuum and spectral line observations. Unique design features include a station-based zoom filter for high spectral resolution, multiple pulsar gates, and a fast dump capability (1 kHz), principally used for pulsar observations. Subsequent data analysis and archiving are carried out to provide feed-back to the mission on data quality.

We describe an aperture synthesis radio tele- scope optimized for studies of the Galactic interstellar medium (ISM), providing the ability to image extended structures with high angular resolution over wide elds. The telescope produces images of atomic hydrogen emis- sion using the 21-cm H i spectral line, and, simultaneously, continuum emission in two bands centred at 1420 MHz and 408 MHz, including linearly polarized emission at 1420 MHz, with synthesized beams of 1 0 and 3:4 0 at the respective frequencies. A full synthesis can achieve a con- tinuum sensitivity (rms) of 0.28 mJy/beam at 1420 MHz and 3.8 mJy/beam at 408 MHz, and the 256-channel H i spectrometer has an rms sensitivity of 3.5B 0:5 sin K per channel, for total spectrometer bandwidth B MHz and declination . The tuning range of the telescope permits studies of Galactic and nearby extragalactic objects. The array uses 9 m antennas, which provide very wide elds of view of 3.1 and 9.6 (at the 10% level), at the two frequencies, and also allow data to be gathered on short baselines, yielding extremely good sensitivity to extended structure. Single-antenna data are also routinely incorpo- rated into images to ensure complete coverage of emission on all angular scales down to the resolution limit. In this paper we describe the telescope and its receiver and corre- lator systems in detail, together with calibration and ob- serving strategies that make this instrument an ecient survey machine.

The Large Adaptive Reflector (LAR), currently being developed at the National Research Council Canada, is a low-cost, large- aperture, wide-band, cm-wave radio telescope designed for implementation in the Square Kilometer Array (SKA). The LAR consists of a 200 m diameter, actuated-surface, parabolic reflector with a feed located at a 500 m focal length. Since the feed must be positioned on a 500 m hemisphere centered about the reflector and between a zenith angle of 0 degree(s) to 60 degree(s), an innovative method for feed positioning is required. This feed positioning will be achieved using a high- tension structure consisting of a 4100 m3 helium aerostat supporting an array of tethers. The length of each tether can be controlled through the use of winches, resulting in accurate control of the feed position. The feasibility of the tethered aerostat feed-positioning system is of critical importance to the success of the LAR. Extensive steady-state analyses of the multi-tethered aerostat have been completed and provide strong evidence that this feed-positioning system will operate reliably in moderate weather conditions (10 m/s constant wind velocity with 2.5 m/s wind gusts). The framework of these analyses and the corresponding results will be presented.