| 1. |
- Connor, Liam, et al.
(författare)
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Galactic Radio Explorer: An All-sky Monitor for Bright Radio Bursts
- 2021
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Ingår i: Publications of the Astronomical Society of the Pacific. - : IOP Publishing. - 0004-6280 .- 1538-3873. ; 133:1025
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Tidskriftsartikel (refereegranskat)abstract
- We present the Galactic Radio Explorer (GReX), an all-sky monitor to probe the brightest bursts in the radio sky. Building on the success of STARE2, we will search for fast radio bursts emitted from Galactic magnetars as well as bursts from nearby galaxies. GReX will search down to similar to ten microseconds time resolution, allowing us to find new super giant radio pulses from Milky Way pulsars and study their broadband emission. The proposed instrument will employ ultra-wide band (0.7-2 GHz) feeds coupled to a high-performance (receiver temperature <10 K) low noise amplifier originally developed for the DSA-110 and DSA-2000 projects. In GReX Phase I (GReX-I), unit systems will be deployed at Owens Valley Radio Observatory and Big Smoky Valley, Nevada. Phase II will expand the array, placing feeds in India, Australia, and elsewhere in order to build up to continuous coverage of nearly 4 pi steradians and to increase our exposure to the Galactic plane. We model the local magnetar population to forecast for GReX, finding the improved sensitivity and increased exposure to the Galactic plane could lead to dozens of FRB-like bursts per year.
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| 2. |
- Flygare, Jonas, 1988, et al.
(författare)
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Strategy and Overview for Development of Beyond-Decade-Bandwidth Quad-ridge Flared Horns for Radio Astronomy
- 2021
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Ingår i: 15th European Conference on Antennas and Propagation, EuCAP 2021.
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Konferensbidrag (refereegranskat)abstract
- This paper considers the potential of the dielectrically loaded Quad-ridge Flared Horn (QRFH) feed to provide continuous beyond-decade bandwidth in reflector telescopes for radio astronomy. An overview of the beam pattern evolution over frequency in a recent ultra-wideband feed designed for 1.5–15.5 GHz is presented.
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| 3. |
- Forkman, Peter, 1959, et al.
(författare)
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Water vapour radiometry in geodetic very long baseline interferometry telescopes: assessed through simulations
- 2021
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Ingår i: Journal of Geodesy. - : Springer Science and Business Media LLC. - 0949-7714 .- 1432-1394. ; 95:11
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Tidskriftsartikel (refereegranskat)abstract
- The accuracy of geodetic Very Long Baseline Interferometry (VLBI) is affected by water vapour in the atmosphere in terms of variations in the signal propagation delay at the different stations. This “wet” delay may be estimated directly from the VLBI data, as well as from independent instruments, such as collocated microwave radiometers. Rather than having stand-alone microwave radiometers we have, through simulations, evaluated the possibility to use radiometric data from the VLBI receiver in the VGOS telescopes at the Onsala Space Observatory. The advantage is that the emission from water vapour, as sensed by the radiometer, originates from the same atmospheric volume that delays the VLBI signal from the extra-galactic object. We use simulations of the sky brightness temperature and the wet delay together with an assumption of a root-mean-square (rms) noise of the receiver of 1 K, and observations evenly spread between elevation angles of 10∘–90∘. This results in an rms error of the estimated equivalent zenith wet delay of the order of 3 mm for a one frequency algorithm, used under cloud free conditions, and 4 mm for a two frequency algorithm, used during conditions with liquid water clouds. The results exclude rainy conditions when the method does not work. These errors are reduced by a factor of 3 if the receiver error is 0.1 K meaning that the receivers’ measurements of the sky brightness temperature is the main error source. We study the impact of ground-noise pickup by using a model of an existing wideband feed. Taking the algorithm uncertainty and the ground noise pickup into account we conclude that the method presented will be useful as an independent estimate of the wet delay to assess the quality of the wet delays and linear horizontal gradients estimated from the VLBI data themselves.
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| 4. |
- Pellegrini, Alice, et al.
(författare)
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MID-Radio Telescope, Single Pixel Feed Packages for the Square Kilometer Array: An Overview
- 2021
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Ingår i: IEEE Journal of Microwaves. - 2692-8388. ; 1:1, s. 428-437
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Tidskriftsartikel (refereegranskat)abstract
- The Square Kilometre Array (SKA) project is an international effort to build the world's largest radio telescope, enabling science with unprecedented detail and survey speed.The project spans over a decade and is now at a mature stage, ready to enter the construction and integration phase. In the fully deployed state, the MID-Telescope consists of a 150-km diameter array of offset Gregorian antennas installed in the radio quiet zone of the Karoo desert (South Africa). Each antenna is equipped with three feed packages, that are precision positioned in the sub-reflector focus by a feed indexer platform. The total observational bandwidth (0.35-15.4GHz) is segmented into seven bands. Band 1 (0.35 – 1.05 GHz) and Band 2 (0.95 – 1.76 GHz) are implemented as individual feed packages. The remaining five bands (Bands 3, 4, 5a, 5b, and 6) are combined in a single feed package. Initially only Band 5a (4.6 – 8.5 GHz) and Band 5b (8.3 – 15.4 GHz) will be installed. This paper provides an overview of recent progress on design, test and integration of each feed package as well as project and science goals, timeline and path to construction.
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