Gary J. Hovey

Demonstration of a Dual-Polarized Phased-Array Feed

We describe the design and construction of a dual-polarized phased-array feed (PAF) with the purpose of demonstrating this technology as a means of expanding the instantaneous field-of-view of radio telescopes. The PAF beamformer is calibrated with observations of an unpolarized astronomical radio source, the covariance matrix of all receiver channels is calculated, and the two dominant eigenvectors are then used as beamformer weights. We show measurements demonstrating the capabilities of this instrument as a polarimeter, and confirm that the calibration method does produce orthogonally-polarized beams. These results are then analyzed to show the sensitivity to fluctuations in gain and phase in the multiple parallel receiver chains making up the phased-array feed. We also compare the performance of PAFs that beamform all array elements with PAFs that beamform only co-polarized elements.

The DRAO Phased Array Feed Demonstrator: Recent results

Future radio telescopes will be used by astronomers to make high-sensitivity wide-band and wide-field surveys of the radio sky. A candidate technology to provide these expanded capabilities is to place high-sensitivity phased-arrays at the focal plane of reflector antennas. Since this technology has not been proven yet, we have constructed the PHased-Array feed Demonstrator (PHAD) with the goal of exploring engineering aspects of this new technology. PHAD comprises 180 densely-packed Vivaldi elements operating from 1 to 2 GHz. Each element feeds a low-noise amplifier and a receiver (both commercial integrated circuits), with the outputs digitized and stored. Beamforming is performed off-line using a matrix language, providing great flexibility in diagnostics and algorithm development. PHAD testing began in a near-field range and has progressed to tests on a dedicated 10-m reflector antenna. Early results (with emphasis on calibration) are reported here.

The first CMOS LNA on a radio telescope

This paper reports on the worlds first CMOS low noise amplifier (LNA) operating successfully on a radio telescope since October 15th, 2010. The radio telescope used in this work is the Synthesis Telescope operated by the Dominion Radio Astrophysical Observatory, NRC, and located near Penticton, BC, Canada. This paper describes the work that led to the installation of the LNA on the telescope and shows measurement results obtained with the telescope.

An update on the mechanical and EM performance of the composite dish verification antenna (DVA-1) for the SKA

This paper will give an overview of the unique mechanical and optical design of the DVA-1 telescope. The rim supported carbon fibre reflector surfaces are designed to be both low cost and have high performance under wind, gravity, and thermal loads. The shaped offset Gregorian optics offer low and stable side lobes along with a large area at the secondary focus for multiple feeds with no aperture blockage. Telescope performance under ideal conditions as well as performance under gravity, wind, and thermal loads will be compared directly using calculated radiation patterns for each of these operating conditions.

Development of a low-noise wide-band phased-array feed

Low-noise phased-array feeds are a new way to expand the field of view of radio telescopes at centimetre wavelengths. First generation engineering demonstrators of this technology have been constructed and tested by several institutes worldwide. The development of second-generation phased-array feeds is now underway. We describe one effort to design and build an astronomy-capable phased-array feed using techniques to reduce front-end noise and increase system bandwidth.

A broadband fpga digital beamformer for the advanced focal array demonstrator (AFAD)

Broadband Focal Array Beamformers offer the potential to increase the field of view of reflector antennas. Such systems require a processing bandwidth of order 1 GHz and need to beamform tens of polarized beams from over 100 array elements. A number of such systems have been built but none with the bandwidth and number of elements required by the Square Kilometre Array. In this paper we outline the digital beamformer for the Advanced Focal Array Demonstrator being developed at the National Research Council¿s Dominion Radio Astrophysical Observatory ¿ a system that meets the bandwidth and beam requirements proposed for the Square Kilometre Array.

JCMT observatory control system

The JCMT, the worlds largest sub-mm telescope, has had essentially the same VAX/VMS based control system since it was commissioned. For the next generation of instrumentation we are implementing a new Unix/VxWorks based system, based on the successful ORAC system that was recently released on UKIRT. The system is now entering the integration and testing phase. This paper gives a broad overview of the system architecture and includes some discussion on the choices made. (Other papers in this conference cover some areas in more detail). The basic philosophy is to control the sub-systems with a small and simple set of commands, but passing detailed XML configuration descriptions along with the commands to give the flexibility required. The XML files can be passed between various layers in the system without interpretation, and so simplify the design enormously. This has all been made possible by the adoption of an Observation Preparation Tool, which essentially serves as an intelligent XML editor.

A high-performance FPGA platform for adaptive optics real-time control

Adaptive Optics Real-Time Control systems for next generation ground-based telescopes demand significantly higher processing power, memory bandwidth and I/O capacity on the hardware platform than those for existing control systems. We present a FPGA based high-performance computing platform that is developed at Dominion Radio Astrophysical Observatory and is very suitable for the applications of Adaptive Optics Real-Time Control systems. With maximum of 16 computing blades, 110 TeraMAC/s processing power, 1.8Terabyte/s memory bandwidth and 19.5 Terabit/s I/O capacity, this ATCA architecture platform has enough capacity to perform pixel processing, tomographic wave-front reconstruction and deformable mirror fitting for first and second generation AO systems on 30+-meter class telescopes. As an example, we demonstrate that with only one computing blade, the platform can handle the real time tomography needs of NFIRAOS, the Thirty-Meter Telescope first light facility Multi-Conjugate Adaptive Optics system. The High- Performance FPGA platform is integrated with Board Software Development Kit to provide a complete and fully tested set of interfaces to access the hardware resources. Therefore the firmware development can be focused on unique, userspecific applications.

New spectral line multibeam correlator system for the James Clerk Maxwell Telescope

A new Auto-Correlation Spectral Imaging System (ACSIS) for the James Clerk Maxwell Telescope (JCMT) is being developed at the National Research Council of Canada, in collaboration with the Joint Astronomy Centre and the United Kingdom Astronomy Technology Centre. The system is capable of computing the integrated power-spectra over 1-GHz bandwidths for up to 32 receiver beams every 50 ms. An innovative, multiprocessor computer will produce calibrated, gridded, 3-D data cubes so that they can be viewed in real-time and are in hand when an observation is over. When connected to arrays of receivers at the Nasmyth focus of the telescope, the system will be able to rapidly make large-scale images with high spectral resolution and map multiple transitions. The ACSIS system will be mated initially with the multibeam 350-GHz receiver system. Heterodyne ARray Program (HARP), under development at the Mullard Radio Astronomy Observatory in Cambridge, England. In this paper we describe ACSIS, how it is designed and the results of key performance tests made.

CryoPAF4: a cryogenic phased array feed design

Phased array feed (PAF) receivers used on radio astronomy telescopes offer the promise of increased fields of view while maintaining the superlative performance attained with traditional single pixel feeds (SPFs). However, the much higher noise temperatures of room temperature PAFs compared to cryogenically-cooled SPFs have prevented their general adoption. Here we describe a conceptual design for a cryogenically cooled 2.8 – 5.18 GHz dual linear polarization PAF with estimated receiver temperature of 11 K. The cryogenic PAF receiver will comprise a 140 element Vivaldi antenna array and low-noise amplifiers housed in a 480 mm diameter cylindrical dewar covered with a RF transparent radome. A broadband two-section coaxial feed is integrated within each metal antenna element to withstand the cryogenic environment and to provide a 50 ohm impedance for connection to the rest of the receiver. The planned digital beamformer performs digitization, frequency band selection, beam forming and array covariance matrix calibration. Coupling to a 15 m offset Gregorian dual-reflector telescope, cryoPAF4 can expect to form 18 overlapping beams increasing the field of view by a factor of ~8x compared to a single pixel receiver of equal system temperature.