NDLI: MeqTrees and direction-dependent effects

Content Provider	IEEE Xplore Digital Library
Author	Smirnov, O.M. de Bruyn, A.G.
Copyright Year	2011
Description	Author affiliation: ASTRON, P.O. Box 2, Dwingeloo, 7900AA, The Netherlands (Smirnov, O.M.; de Bruyn, A.G.)
Abstract	The classical self-calibration algorithm employed in radio interferometry associates a single direction-independent complex gain term (which can have a complicated behaviour in frequency and time) with each antenna of the interferometer. This has been spectacularly successful, and has allowed dynamic range (DR) in excess of $10^{6}:1$ to be reached [1], but only for relatively narrow fields with a single dominant source of emission. In many other regimes of current and future instruments, direction-dependent effects (DDEs) — that is, effects that vary across the field of view (FoV) as well as between antennas — become significant enough to produce DR-limiting calibration artefacts. The Westerbork Synthesis Radio Telescope (WSRT) is a particularly low-DDE instrument due to its careful design, but at sufficiently high DR, clear DDE-related artefacts are also evident (Fig. 1, left). In a previous study [2], we applied the differential gains (DG) technique using the MeqTrees package [3] to eliminate these artefacts. This was very successful at producing a noise-limited image (Fig. 1, right), but did not explain the ultimate cause of the DDEs in the 3C 147 dataset. The per-antenna DG solutions for the 3C 147 field showed continuity in time and consistency across frequency bands [2], which was a clear indication of some “global” effect at work. Crucially, this also demonstrated that sources as faint as few mJy could be used to solve for differential gains, and could thus be employed as “calibration beacons” in the various closed-loop methods proposed for the calibration of DDEs.
Starting Page	1
Ending Page	4
File Size	3260231
Page Count	4
File Format	PDF
ISBN	9781424451173
e-ISBN	9781424460519
DOI	10.1109/URSIGASS.2011.6051222
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	2011-08-13
Publisher Place	Turkey
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Observatories Noise Radio interferometry Telescopes Dynamic range Calibration Antennas
Content Type	Text
Resource Type	Article

Sl.	Authority	Responsibilities	Communication Details
1	Ministry of Education (GoI), Department of Higher Education	Sanctioning Authority	https://www.education.gov.in/ict-initiatives
2	Indian Institute of Technology Kharagpur	Host Institute of the Project: The host institute of the project is responsible for providing infrastructure support and hosting the project	https://www.iitkgp.ac.in
3	National Digital Library of India Office, Indian Institute of Technology Kharagpur	The administrative and infrastructural headquarters of the project	Dr. B. Sutradhar bsutra@ndl.gov.in
4	Project PI / Joint PI	Principal Investigator and Joint Principal Investigators of the project	Dr. B. Sutradhar bsutra@ndl.gov.in Prof. Saswat Chakrabarti will be added soon
5	Website/Portal (Helpdesk)	Queries regarding NDLI and its services	support@ndl.gov.in
6	Contents and Copyright Issues	Queries related to content curation and copyright issues	content@ndl.gov.in
7	National Digital Library of India Club (NDLI Club)	Queries related to NDLI Club formation, support, user awareness program, seminar/symposium, collaboration, social media, promotion, and outreach	clubsupport@ndl.gov.in
8	Digital Preservation Centre (DPC)	Assistance with digitizing and archiving copyright-free printed books	dpc@ndl.gov.in
9	IDR Setup or Support	Queries related to establishment and support of Institutional Digital Repository (IDR) and IDR workshops	idr@ndl.gov.in

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