Date: October 10, 2006

Time: 4:00 p.m.

Location: Centergy One 5186

Speaker(s): Dr. Alle-Jan van der Veen, Delft University of Technology, Netherland

Title: Self Calibration for the LOFAR Radio Astronomical Array

Abstract:
LOFAR (www.lofar.org) is a low frequency radio astronomical array currently under development in The Netherlands. It is designed to produce synthesis images of the most distant celestial objects yet observed. Due to high red shift levels, observations must be at unusually low frequencies (30-240 MHz), over large apertures (100 km), using thousands of antennas. At these frequencies the Earth's ionosphere acts as a random refractive sheet which over the large aperture induces source direction dependent gain and phase errors that must be estimated and calibrated out. Current radio astronomy "self calibration" algorithms do not address direction dependence and will not work in the LOFAR environment. The presentation considers the parameter estimation problem for LOFAR calibration. It is shown that although the unconstrained direction dependent calibration problem is ambiguous, physically justifiable constraints can be applied in LOFAR to yield viable solutions.

Bio:
Alle-Jan van der Veen received the Ph.D. degree (cum laude) in Electrical Engineering in 1993 from TU Delft, The Netherlands. At present, he is a Full Professor in the Signal Processing group of DIMES, Delft University of Technology. He is a Fellow of the IEEE. He is the recipient of a 1994 and a 1997 IEEE Signal Processing Society Young Author paper award. He was chairman of the IEEE Technical Committee on Signal Processing for Communications and Editor-in-Chief of IEEE Signal Processing Letters (2002-2005). He is currently Editor-in-Chief of IEEE Transactions on Signal Processing (2006-2008), and an elected Member-at-Large of the IEEE Signal Processing Society Board of Governors (2006-2008). His research interests are in the areas of signal processing for communications, array signal processing, and in particular in linear algebra techniques applied to these areas. Website: http://cas.et.tudelft.nl/~allejan/

Date:	October 10, 2006
Time:	4:00 p.m.
Location:	Centergy One 5186
Speaker(s):	Dr. Alle-Jan van der Veen, Delft University of Technology, Netherland
Title:	Self Calibration for the LOFAR Radio Astronomical Array
Abstract:	LOFAR (www.lofar.org) is a low frequency radio astronomical array currently under development in The Netherlands. It is designed to produce synthesis images of the most distant celestial objects yet observed. Due to high red shift levels, observations must be at unusually low frequencies (30-240 MHz), over large apertures (100 km), using thousands of antennas. At these frequencies the Earth's ionosphere acts as a random refractive sheet which over the large aperture induces source direction dependent gain and phase errors that must be estimated and calibrated out. Current radio astronomy "self calibration" algorithms do not address direction dependence and will not work in the LOFAR environment. The presentation considers the parameter estimation problem for LOFAR calibration. It is shown that although the unconstrained direction dependent calibration problem is ambiguous, physically justifiable constraints can be applied in LOFAR to yield viable solutions.
Bio:	Alle-Jan van der Veen received the Ph.D. degree (cum laude) in Electrical Engineering in 1993 from TU Delft, The Netherlands. At present, he is a Full Professor in the Signal Processing group of DIMES, Delft University of Technology. He is a Fellow of the IEEE. He is the recipient of a 1994 and a 1997 IEEE Signal Processing Society Young Author paper award. He was chairman of the IEEE Technical Committee on Signal Processing for Communications and Editor-in-Chief of IEEE Signal Processing Letters (2002-2005). He is currently Editor-in-Chief of IEEE Transactions on Signal Processing (2006-2008), and an elected Member-at-Large of the IEEE Signal Processing Society Board of Governors (2006-2008). His research interests are in the areas of signal processing for communications, array signal processing, and in particular in linear algebra techniques applied to these areas. Website: http://cas.et.tudelft.nl/~allejan/