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Despeckling is a crucial noise reduction task in improving the quality of synthetic aperture radar (SAR) images. Directly obtaining noise-free SAR images is a challenging task that has hindered the development of accurate despeckling…

Computer Vision and Pattern Recognition · Computer Science 2024-01-17 Shunya Kato , Masaki Saito , Katsuhiko Ishiguro , Sol Cummings

In the context of computer models, calibration is the process of estimating unknown simulator parameters from observational data. Calibration is variously referred to as model fitting, parameter estimation/inference, an inverse problem, and…

Methodology · Statistics 2023-10-16 Richard D. Wilkinson , Christopher W. Lanyon

(Abridged) The CASA software suite, can now reduce very long baseline interferometry (VLBI) data with the recent addition of a fringe fitter. Here, we present the Radboud PIpeline for the Calibration of high Angular Resolution Data…

A crucial part of a space mission for very-long baseline interferometery (VLBI), which is the technique capable of providing the highest resolution images in astronomy, is orbit determination of the mission's space radio telescope(s). In…

We present recent improvements in polarization analysis with the INTEGRAL SPI data. The SPI detector plane consists of 19 independent Ge crystals and can operate as a polarimeter. The anisotropy characteristics of Compton diffusions can…

Instrumentation and Methods for Astrophysics · Physics 2015-06-15 M. Chauvin , J. P. Roques , D. J. Clark , E. Jourdain

This paper presents the fifth part of the Very Long Baseline Array (VLBA) Calibrator Survey (VCS), containing 569 sources not observed previously with very long baseline interferometry in geodetic or absolute astrometry programs. This…

Astrophysics · Physics 2008-11-26 Y. Y. Kovalev , L. Petrov , E. B. Fomalont , D. Gordon

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…

Fourier ptychography captures intensity images with varying source patterns (illumination angles) in order to computationally reconstruct large space-bandwidth-product images. Accurate knowledge of the illumination angles is necessary for…

Signal Processing · Electrical Eng. & Systems 2018-11-01 Regina Eckert , Zachary F. Phillips , Laura Waller

We benchmark the reliability of the Rotation Measure (RM) synthesis algorithm using the 1005 Centaurus A field sources of Feain et al. (2009). The RM synthesis solutions are compared with estimates of the polarization parameters using…

Instrumentation and Methods for Astrophysics · Physics 2015-06-04 J. -P. Macquart , R. D. Ekers , I. Feain , M. Johnston-Hollitt

The alignment between the radio-based International Celestial Reference Frame (ICRF) and the optical Gaia Celestial Reference Frame (Gaia-CRF) is critical for multi-waveband astronomy, yet systematic offsets at the optical bright end (G<13)…

We present an algorithm to photometrically calibrate wide field optical imaging surveys, that simultaneously solves for the calibration parameters and relative stellar fluxes using overlapping observations. The algorithm decouples the…

The development of sensitive large format imaging arrays for the infrared promises to provide revolutionary capabilities for space astronomy. For example, the Infrared Array Camera (IRAC) on SIRTF will use four 256 x 256 arrays to provide…

Astrophysics · Physics 2016-08-30 D. J. Fixsen , S. H. Moseley , R. G. Arendt

We present an iterative scheme designed to recover calibrated I, Q, and U maps from Planck-HFI data using the orbital dipole due to the satellite motion with respect to the Solar System frame. It combines a map reconstruction, based on a…

Cosmology and Nongalactic Astrophysics · Physics 2015-03-19 M. Tristram , C. Filliard , O. Perdereau , S. Plaszczynski , R. Stompor , F. Touze

The linear polarization images of the jet in the giant elliptical galaxy M87 have previously been observed with Very Long Baseline Array at 7 mm. They exhibit a complex polarization structure surrounding the optically thick and compact…

High Energy Astrophysical Phenomena · Physics 2021-12-08 Jongho Park , Keiichi Asada , Masanori Nakamura , Motoki Kino , Hung-Yi Pu , Kazuhiro Hada , Evgeniya V. Kravchenko , Marcello Giroletti

We describe the POLAMI program for the monitoring of all four Stokes parameters of a sample of bright radio-loud active galactic nuclei with the IRAM 30m telescope at 3.5 and 1.3mm. The program started in October 2006 and accumulated, until…

The recent development of $\theta\mhyphen\theta$ techniques in pulsar scintillometry has opened the door for new high resolution imaging techniques of the scattering medium. By solving the phase retrieval problem and recovering the…

Instrumentation and Methods for Astrophysics · Physics 2023-08-09 Daniel Baker , Walter Brisken , Marten H. van Kerkwijk , Rik van Lieshout , Ue-Li Pen

Pooling biomarker data across multiple studies enables researchers to get more precise estimates of the association between biomarker exposure measurements and disease risks due to increased sample sizes. However, biomarker measurements…

Methodology · Statistics 2019-11-22 Yujie Wu , Mitchell H. Gail , Stephanie A. Smith-Warner , Regina G. Ziegler , Molin Wang

Bayesian calibration of computer models tunes unknown input parameters by comparing outputs with observations. For model outputs that are distributed over space, this becomes computationally expensive because of the output size. To overcome…

Methodology · Statistics 2018-10-05 Kai-Lan Chang , Serge Guillas

A new method is presented for modeling the transformation between two polarimetric pulse profiles in the Fourier domain. In practice, one is a well-determined standard with high signal-to-noise ratio and the other is an observation that is…

Astrophysics · Physics 2007-05-23 Willem van Straten