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200 papers

We report on a recent 90 cm wide-field VLBI survey of two 3.1 deg^2 fields using the VLBA, Westerbork and Jodrell Bank telescopes. In-beam calibration was used to calibrate each field, the process was simplified by imaging the calibrators…

Astrophysics · Physics 2007-05-23 Emil Lenc , Mike A. Garrett , Olaf Wucknitz , James M. Anderson , Steven J. Tingay

We have combined high resolution VLBI Space Observatory Programme (VSOP) data at 1.6 and 4.8 GHz with Very Long Baseline Array (VLBA) data at higher frequencies and with similar resolutions to study the spectral properties of the core of…

Astrophysics · Physics 2015-06-24 Richard Dodson , Philip G. Edwards , Hisashi Hirabayashi

Model-independent distance constraints to binary millisecond pulsars (MSPs) are of great value to both the timing observations of the radio pulsars, and multiwavelength observations of their companion stars. Very Long Baseline…

Fifth-generation (5G) cellular systems will build on massive multi-user (MU) multiple-input multiple-output (MIMO) technology to attain high spectral efficiency. However, having hundreds of antennas and radio-frequency (RF) chains at the…

Signal Processing · Electrical Eng. & Systems 2018-03-02 Oscar Castañeda , Sven Jacobsson , Giuseppe Durisi , Tom Goldstein , Christoph Studer

The Atacama Large mm-submm Array (ALMA) is, by far, the most sensitive mm/submm telescope in the World. The ALMA Phasing Project (APP) will allow us to phase-up all the ALMA antennas and use them as one single VLBI station. This will be a…

Instrumentation and Methods for Astrophysics · Physics 2015-04-27 I. Marti-Vidal , A. Roy , W. Alef , J. Conway , M. Lindqvist , A. J. Zensus

We present the results of the pilot observations of the Deep Extragalactic VLBI-Optical Survey (DEVOS). Our ultimate aim is to collect information on compact structures in a large sample of extragalactic radio sources (~10000 objects) up to…

Astrophysics · Physics 2009-11-13 L. Mosoni , S. Frey , L. I. Gurvits , M. A. Garrett , S. T. Garrington , Z. I. Tsvetanov

We report the results of a 5-GHz southern-hemisphere snapshot VLBI observation of a sample of blazars. The observations were performed with the Southern Hemisphere VLBI Network plus the Shanghai station in 1993 May. Twenty-three…

We have carried out full imaging simulation studies to explore the impact of frequency standards in millimeter and sub-millimeter Very Long Baseline Interferometry (VLBI), focusing on the coherence time and sensitivity. In particular, we…

Instrumentation and Methods for Astrophysics · Physics 2015-06-11 M. Rioja , R. Dodson , Y. Asaki , J. Hartnett , S. Tingay

This paper addresses simultaneous, high-precision measurement and analysis of generic reference signals by using inexpensive commercial off-the-shelf Software Defined Radio hardware. Sine reference signals are digitally down-converted to…

Signal Processing · Electrical Eng. & Systems 2018-04-12 Carsten Andrich , Alexander Ihlow , Julia Bauer , Niklas Beuster , Giovanni Del Galdo

We present images of NRAO530 observed with the EVN (VLBI) at 5 GHz, the MERLIN at 1 .6 and 5 GHz, and the VLA at 5 and 8 GHz showing the complex morphology on scales from pc to kpc. The VLBI image shows a core-jet structure indicating a…

Astrophysics · Physics 2007-05-23 X. Y. Hong , J. H. Zhao , T. An , D. R. Jiang , H. Wang , W. X. Feng , C. H. Sun

An X-ray detector will be presented that is the combination of a segmented ionization chamber featuring one-dimensional spatial resolution integrated with an intelligent ADC front-end, multi DSP processing and embedded PC platform. This…

Instrumentation and Detectors · Physics 2010-01-26 Francesco Voltolina , Ralf H. Menk , Sergio Carrato

A new technique has been developed to remove the ionosphere's distorting effects from low frequency VLBI data. By fitting dispersive and non-dispersive components to the phases of multi-frequency data, the ionosphere can be effectively…

We report on an ongoing effort to image active galactic nuclei simultaneously observed at 2.3 and 8.6 GHz in the framework of a long-term VLBI project RDV (Research and Development - VLBA) started in 1994 aiming to observe compact…

Astrophysics · Physics 2008-12-31 A. B. Pushkarev , Y. Y. Kovalev

The demand for energy-efficient and high performance embedded systems drives the evolution of new hardware architectures, including concepts like approximate computing. This paper presents a novel reconfigurable embedded platform named…

Hardware Architecture · Computer Science 2024-10-02 Arvin Delavari , Faraz Ghoreishy , Hadi Shahriar Shahhoseini , Sattar Mirzakuchaki

Very-long-baseline interferometry (VLBI) at frequencies above 230 GHz with Earth-diameter baselines gives spatial resolution finer than the ${\sim}50 \mu$as "shadow" of the supermassive black hole at the Galactic Center, Sagittarius A* (Sgr…

Instrumentation and Methods for Astrophysics · Physics 2019-08-21 Daniel C. M. Palumbo , Sheperd S. Doeleman , Michael D. Johnson , Katherine L. Bouman , Andrew A. Chael

The VSOP mission is a Japanese-led project to study radio sources with sub-milliarcsecond angular resolution using an orbiting 8-m telescope, HALCA and global arrays of Earth-based telescopes. Approximately 25% of the observing time has…

We present total and linearly polarized 3 mm Global mm-VLBI Array images of a sample of blazars and radio galaxies from the VLBA-BU-BLAZAR 7 mm monitoring program designed to probe the innermost regions of active galactic nuclei (AGN) jets…

We report the development of a semi-automatic pipeline for the calibration of 86 GHz full-polarization observations performed with the Global Millimeter-VLBI array (GMVA) and describe the calibration strategy followed in the data reduction.…

Instrumentation and Methods for Astrophysics · Physics 2015-06-04 I. Marti-Vidal , T. P. Krichbaum , A. Marscher , W. Alef , A. Bertarini , U. Bach , F. K. Schinzel , H. Rottmann , J. M. Anderson , J. A. Zensus , M. Bremer , S. Sanchez , M. Lindqvist , A. Mujunen

A modern Q-band low noise amplifier (LNA) front-end is being fitted to the 10.4 m millimeter-wave telescope at the Raman Research Institute (RRI) to support observations in the 40-50 GHz frequency range. To assess the suitability of the…

Instrumentation and Methods for Astrophysics · Physics 2009-10-16 Ramesh Balasubramanyam , Suresh Venkatesh , Sharath B. Raju