119 research outputs found
Measured Sensitivity of the First Mark II Phased Array Feed on an ASKAP Antenna
This paper presents the measured sensitivity of CSIRO's first Mk. II phased
array feed (PAF) on an ASKAP antenna. The Mk. II achieves a minimum
system-temperature-over-efficiency of 78 K at 1.23 GHz
and is 95 K or better from 835 MHz to 1.8 GHz. This PAF was designed for the
Australian SKA Pathfinder telescope to demonstrate fast astronomical surveys
with a wide field of view for the Square Kilometre Array (SKA).Comment: 5 pages, 2 figures, accepted for publication in Electromagnetics in
Advanced applications (ICEAA), 2015 International Conference o
The Murchison Widefield Array: the Square Kilometre Array Precursor at low radio frequencies
The Murchison Widefield Array (MWA) is one of three Square Kilometre Array
Precursor telescopes and is located at the Murchison Radio-astronomy
Observatory in the Murchison Shire of the mid-west of Western Australia, a
location chosen for its extremely low levels of radio frequency interference.
The MWA operates at low radio frequencies, 80-300 MHz, with a processed
bandwidth of 30.72 MHz for both linear polarisations, and consists of 128
aperture arrays (known as tiles) distributed over a ~3 km diameter area. Novel
hybrid hardware/software correlation and a real-time imaging and calibration
systems comprise the MWA signal processing backend. In this paper the as-built
MWA is described both at a system and sub-system level, the expected
performance of the array is presented, and the science goals of the instrument
are summarised.Comment: Submitted to PASA. 11 figures, 2 table
The Commensal Real-time ASKAP Fast Transients (CRAFT) survey
We are developing a purely commensal survey experiment for fast (<5s)
transient radio sources. Short-timescale transients are associated with the
most energetic and brightest single events in the Universe. Our objective is to
cover the enormous volume of transients parameter space made available by
ASKAP, with an unprecedented combination of sensitivity and field of view. Fast
timescale transients open new vistas on the physics of high brightness
temperature emission, extreme states of matter and the physics of strong
gravitational fields. In addition, the detection of extragalactic objects
affords us an entirely new and extremely sensitive probe on the huge reservoir
of baryons present in the IGM. We outline here our approach to the considerable
challenge involved in detecting fast transients, particularly the development
of hardware fast enough to dedisperse and search the ASKAP data stream at or
near real-time rates. Through CRAFT, ASKAP will provide the testbed of many of
the key technologies and survey modes proposed for high time resolution science
with the SKA.Comment: accepted for publication in PAS
Observing Pulsars with a Phased Array Feed at the Parkes Telescope
During February 2016, CSIRO Astronomy and Space Science and the
Max-Planck-Institute for Radio Astronomy installed, commissioned and carried
out science observations with a phased array feed (PAF) receiver system on the
64m diameter Parkes radio telescope. Here we demonstrate that the PAF can be
used for pulsar observations and we highlight some unique capabilities. We
demonstrate that the pulse profiles obtained using the PAF can be calibrated
and that multiple pulsars can be simultaneously observed. Significantly, we
find that an intrinsic polarisation leakage of -31dB can be achieved with a PAF
beam offset from the centre of the field of view. We discuss the possibilities
for using a PAF for future pulsar observations and for searching for fast radio
bursts with the Parkes and Effelsberg telescopes.Comment: 10 pages, 8 figures, 2 tables. It has been accepted for publication
in PAS
A GPU based Transient Dedisersion Search Engine for CRAFT
The Commensal Realtime ASKAP Fast Transient Survey (CRAFT[5]) will search the ASKAP data stream for fast (< 5sec) transient events, associated with the most extreme conditions in the Universe. The CRAFT search will run in parallel with all normal observing on ASKAP, giving a tremendous advance in the transient parameter space which can be searched. ASKAP offers high sensitivity, high resolution, and continous observations of a significant portion of the sky. However, to search across the wide field of view and at the data rates which are being provided by ASKAP is extremely challenging. Nevertheless, as reported here, we are on track to achieve the goals as laid out in the Survey Science Proposal. Using GPUs as a simple highly parallel compute-engine we can monitor the full field of view with a 5(sigma) sensitivity of ~Jy for a millisecond event covering the astronomically significant range of DMs. After that trigger detection we can download the beamformer data-buffer and image the sky at full sensitivity and spatial resolution with an arbitary frequency and time resolution
Phased Array Feed Calibration, Beamforming and Imaging
Phased array feeds (PAFs) for reflector antennas offer the potential for
increased reflector field of view and faster survey speeds. To address some of
the development challenges that remain for scientifically useful PAFs,
including calibration and beamforming algorithms, sensitivity optimization, and
demonstration of wide field of view imaging, we report experimental results
from a 19 element room temperature L-band PAF mounted on the Green Bank
20-Meter Telescope. Formed beams achieved an aperture efficiency of 69% and
system noise temperature of 66 K. Radio camera images of several sky regions
are presented. We investigate the noise performance and sensitivity of the
system as a function of elevation angle with statistically optimal beamforming
and demonstrate cancelation of radio frequency interference sources with
adaptive spatial filtering.Comment: 19 pages, 13 figure
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