The RadioAstron Dedicated DiFX Distribution

Gabriele Bruni,Helge Rottmann,James Anderson,Walter Alef,J Zensus,Andrei Lobanov

doi:10.3390/galaxies4040055

Gabriele Bruni, Helge Rottmann + Show 4 more

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https://doi.org/10.3390/galaxies4040055

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Journal: Galaxies	Publication Date: Oct 27, 2016
Citations: 22	License type: CC BY 4.0

Affiliation: Max Planck Institute for Radio Astronomy

Abstract

Distributed FX-architecture (DiFX) is a software Very Long Baseline Interferometry (VLBI) correlator currently adopted by several main correlation sites around the globe. After the launch of the RadioAstron Space-VLBI mission in 2011, an extension was necessary to handle processing of an orbiting antenna, to be correlated with supporting ground arrays. Here, we present a branch of the main DiFX distribution (2.4), uploaded on the publicly available repository during July 2016, that the Max Planck Institute for Radio Astronomy (MPIfR) developed to process data of the three key active galactic nuclei (AGN)-imaging RadioAstron science projects, as well as part of the AGN survey project, and General Observing Time (GOT) projects proposed since Announcement of Opportunity 2 (AO-2, July 2014–July 2015). It can account for general relativistic correction of an orbiting antenna with variable position/velocity, providing a routine to convert the native RadioAstron Data Format (RDF) format to the more common Mark5 B (M5B). The possibility of introducing a polynomial clock allows one to mitigate the effects of spacecraft acceleration terms in near-perigee observations. Additionally, since for the first time polarimetry on space-baselines is available thanks to RadioAstron, this DiFX branch allows one to include the spacecraft orientation information at the correlation stage, in order to perform proper polarization calibration during data reduction. Finally, a fringe-finding algorithm able to manage an arbitrarily large fringe-search window is included, allowing one to increase the search space normally adopted by common software packages like HOPS.

Highlights

The Distributed FX-architecture (DiFX) software correlator was first introduced in 2007 [1] to offer a versatile alternative to the previous generation of hardware correlators
In 2011, a second version was made available to the community (DiFX-2, [2]), including a number of improvements and new utilities, including multiple phase-center correlation in a single pass, phase-calibration tones extraction for geodetic applications, zoom-mode for correlation of disparate but overlapping sub-bands, full support for VDIF data format, arbitrary-order polynomial clock, and many more
The RadioAstron space radio telescope was launched in July 2011 by the Russian space agency (Roscosmos) and it is led by Astro Space Center (ASC, Moscow)

Summary

Introduction

The Distributed FX-architecture (DiFX) software correlator was first introduced in 2007 [1] to offer a versatile alternative to the previous generation of hardware correlators. In 2011, a second version was made available to the community (DiFX-2, [2]), including a number of improvements and new utilities, including multiple phase-center correlation in a single pass, phase-calibration tones extraction for geodetic applications, zoom-mode for correlation of disparate but overlapping sub-bands, full support for VDIF data format, arbitrary-order polynomial clock, and many more. The RadioAstron space radio telescope was launched in July 2011 by the Russian space agency (Roscosmos) and it is led by Astro Space Center (ASC, Moscow).

Results

Conclusion